Look East in December 2013 – take the Pleiades challenge!

“Glitter like a swarm of fireflies, Tangled in a silver braid.”  – (Words from Tennyson, photo from NASA.) No you don’t see the Pleiades star cluster quite like this with your naked eye, but binoculars and small telescopes give you an awesome view. I should add, however, that the nebulosity that surrounds them is difficult to see even with optical aid.

The focus for those learning the stars this month is the beautiful star cluster, the Pleiades, and while charming to those with dark skies and good eyesight,  I guarantee you it will look far better in just about any binoculars you point towards it.   When you look east starting about 45 minutes to an hour after sunset, here’s what you should see.

Click imager for larger version. (Prepared from Starry Nights Pro screen shot.)

Go here to download a printer-friendly version of this chart.

Capella, which we met last month, dominates the northeast and now it’s easy to pick out the familiar kite figure which, lead by Capella, covers the heart of the constellation Auriga. About parallel with Capella, but south of it will be the Pleiades – but don’t expect to see them well until it gets darker. You may pick them up with binoculars an hour after sunset, but to really appreciate them, wait an hour and a half after sunset.

East of the Pleiades – below it as you look at the eastern sky – is the bright guidepost star, Aldebaran. It highlights a “V” asterism that marks the head of Taurus the Bull. Dominant as it is, imagine just for a moment what it would be like if Aldebaran were our Sun. James Kaler points out that it would span 20 degrees in our sky – our Sun spans half a degree! So rising in the east, it would nearly fill the space between the Pleiades and the horizon. Get the following vision of Aldebaran in your head as you gaze to the east on a December evening.

Aldebaran, looking like the “Great Pumpkin” of Peanuts comic fame, would overwhelm us with its orange brilliance and dominate our sky if it were as close to us as our Sun. (Actually, if we were this close to Aldebaran we would be overwhelmed – charred to a crisp!)

Aldebaran is what is classified as a “giant,”  and it is indeed huge when compared to our Sun, but there are many stars much larger. It’s the 14th brightest star in our sky – compare it to Capella and you will notice that Capella is  brighter.  Aldebaran is 67 light years away – reasonably close – and in the ecliptic – the path the Sun, Moon, and planets take in our sky. This means it frequently flirts with Mars and at such times it’s fun to compare the color of these two reddish objects. It also gets occulted, from time to time, by our Moon – meaning the Moon passes in front of it. Its surface temperature is a bit lower than our Sun’s, thus the orange tint. It radiates quite a lot of its energy in infrared and is about 425 times as luminous as our Sun.

Vital stats for Aldebaran (al-DEB-ah-ran)

• Brilliance: Magnitude .85; its luminosity is the equal of 425 Suns.
• Distance: 67 light years
• Spectral Types: K5
• Position: 04:36, +16:32

Aldebaran appears to be the brightest star in another star cluster, the Hyades. In reality, it is not part of that cluster, for it’s much closer to us.  Its name – Aldebaran – means “follower” – for it appears to follow the Pleiades up the sky.  (Actually, skywatchers sometimes use the terms “precedes” and “follows” to indicate sky direction. A star that “follows” is to the east of the object it is following – and one that precedes, is to the west.)

In classical depictions of the constellations, Aldebaran is the “bull’s eye,” and  the “V” of stars near it is the bull’s head. But that V is, as mentioned ,  another open star cluster, the Hyades.

Taurus, as depicted in Uranometria (Bayer, 1603), showing Aldebran as one of his eyes. (Used with permission from the  Linda Hall Library of Science, Engineering, & Technolog.)

Hyades and Pleiades

Now what’s fun here is to pause a moment and go back and forth between the Hyades and the Pleiades. Both are open star clusters, and in reality they cover roughly the same area of space – about a dozen light years – but, you will notice immediately that the Hyades appear much larger. There’s a simple reason for that – the Hyades are just 151 light years away, while the Pleiades are more like 400 light years from us.

A careful observer will also notice that the Hyades tend to be yellowish stars, while the Pleiades are icy, blue diamonds. That’s because the Hyades at 660 million years are about ten times as old as the Pleiades. Of course, in astronomical terms both contain young stars, our Sun being about 5 billion years old and our galaxy something like 12 billion years. But the few hundred million years of age the Hyades has over the Pleiades means it does contain more yellow stars.

One more thing you might notice about the Pleiades – they look like a tiny dipper – in fact, I’ve had more than one visitor ask me if this is the “Little Dipper.” I guess you could call it “The Littlest Dipper!” You also could call it “Subaru.”   That’s the Japanese name  for  this little purse of celestial gemstones,  and the car maker does include them in its logo. And here are a couple of Pleiades challenges for you:

1. How many Pleiads can you see with the naked eye?

2. And can you see – with naked eye, binoculars, or telescope – the faint nebulosity that surrounds these stars?

It was that nebulosity that apparently inspired Alfred Lord Tennyson as he penned this famous tribute in “Lockesley Hall”:

Many a night I saw the Pleiades,
Rising thro’ the mellow shade,
Glitter like a swarm of fireflies
Tangled in a silver braid.

Beautiful, but no words or image can do justice to the live, real-time experience of standing outside on a crisp December evening, raising binoculars to your eyes, and seeing these icy diamonds! (Oh they can be seen with the naked eye, but binoculars give a much better view.)

Even without binoculars, the Pleiades can be quite dazzling for those with good eyes and dark skies. Not me. With my aging eyes they tend to blend together, and even when I put my glasses on I can only with care see four or five separate stars. Younger eyes do much better.

So how many stars do you see? Take your time. Patience is the key. I suggest you get a comfortable beach chair, lean back, relax, and look for at least a solid minute at a time.  How many should you see? I suspect most people who take the time to observe carefully get as many as six to 10.  Walter Scott Houston, who wrote a Sky and Telescope magazine column when astronomy was new to me in the 1950s, counted 18 with the naked eye! And the visual observer I most  admire today, Stephen James O’Meara, says in his book “The Messier Objects:”

Although largely symbolic, the age-old association of the Pleiades with the number seven remains fixed to this day – to the point that some observers swear they cannot see more than seven members, even though the Pleiades contains 10 stars brighter than 6th magnitude. Some observers question how it is possible to see 10 Pleiads in The Seven Sisters (a demonstration of the power of words . . . ) The fact is that almost three times that magic number of stars can be seen without magnification by an astute observer under dark skies.

O’Meara says he logged 17 while observing in Cambridge, MA – which hardly has dark skies.  “The trick,” he says, “is to spend a lot of time looking and plotting.” This business of “time on target” is something I find hard to convey to new observers. But it is the key. Another key is simply experience. I frequently see things that those with younger eyes don’t see, simply because I’ve seen them before and know exactly what to expect. Crossen and Tirion in their book “Binocular Astronomy” have this general piece of advice, which certainly applies here:

When I first began observing with binoculars I could not see the Rosette Nebula at all, but now it is not difficult for me even under poor sky conditions.
The most important thing in observing is to really look – a mere glance at an object or a field is simply not enough. You must keep your eye at the oculars for at least a full minute at a time.

That said, don’t let the numbers and reports by others discourage you – the Pleiades are yours to enjoy no matter how many you count.  Another noted popular astronomy author, Terrence Dickinson, writes in his book “Nightwatch,” that he has “a tough time seeing more than six stars with the unaided eye, even under excellent conditions,” but he also notes that some of his “astronomy students have reported seeing as many as 11.”

And turn binoculars on them and you should be able to easily count between 25 and 50.

The second challenge is more subtle. It involves the nebulosity that shows up in nearly every photograph of this cluster. No, don’t go looking for such a photograph. It will only prejudice you as to both the nebulosity and the fainter stars – and besides, you’ll never match a long exposure photograph with your eyes because film, or the modern CCD accumulate  much more light than our eyes.

The Pleiades, as I mentioned, are “young” stars – about 100 million years old, and in astronomical terms that means they’re mere babes. (Our star – the Sun – is about 5 billion years old. ) The Pleiades are not far removed from the cosmic womb of gas and dust in which they were formed. Until fairly recently it was assumed that this nebulosity we see was the last wispy remains of the nebulae in which the Pleiades were formed. Today it is more generally thought that this nebulosity is just a happy accident – an entirely different gossamer cloud of gas and dust that is reflecting the brilliant light of the Pleiades as they pass through it.

In any event, Tennyson seems to reference it when he refers to his “swarm of fireflies” being in a “tangled braid.“  When I look with the naked eye I certainly don’t see it. But be careful. A couple of these stars are quite bright, and because they’re close together, their light tends to blend and perhaps give the impression of being surrounded by nebulosity. Perhaps that’s all Tennyson saw, especially as the stars were near the horizon – or at least that’s where he puts them in his poem.

So while I assume Tennyson was talking about a naked eye view and perhaps glimpsed the nebulosity in pristine Victorian skies free of modern light pollution, I feel this second challenge is best pursued with binoculars and small telescopes.  While there is nebulosity near several stars, the brightest part is southeast of Merope. (Merope is identified in the downloadable charts at the end of this section.)  So I would look for this first.  What you need to do is look for a difference in the darkness of the background sky in this region. Using binoculars move away from the cluster a tad to avoid the glare – see how dark the sky is? Now move closer to it – do you detect any change in the background brightness?  Again, be careful you don’t confuse the glow around a bright star with nebulosity.

When you think you have spotted the nebulosity, it would be helpful to quickly sketch its location on the provided chart – then compare it with a picture of the Pleiades, such as this one, to see  if your impression of the location and size of the nebulosity matches what the camera reveals.

When to look

To take the challenge you want the Pleiades high in a dark – moonless – sky. In December of 2013  thef first and last weeks will be the best time to see the Pleiades in relatively Moonless skies at a reasonable hour.

This is a good lesson, however, for looking at any faint astronomical object. When we do that we are constantly balancing these different factors of how high the object is above the horizon – the higher the better because the higher it is the less atmosphere you need to look through to see it – and where the Moon is, because it is constantly changing position and brightness, and it tends to wash out the sky anywhere near it.  But as you can see, there’s at least a two-week window when you can take the Pleiades’ challenge – assuming the weather cooperates! And, of course, the Pleiades will still be with us through the winter.

Some helpful charts

Click image for larger version. (This chart is derived from a Starry Nights Pro screen shot. A printer friendly version appears in the links at the end of this post.)

There are three printer-friendly charts listed here, but for starters I suggest you download only the first two. They both show the brightest Pleiads but the second one has no names on it and is meant for you to use – and add to – when taking either challenge. Put it on a clipboard and take it, a pencil, and a soft red light to your observing location. Then when you spot a faint star you can mark its location in relation to the brightest stars. Once you’ve done this, take a look at the third chart which shows the Pleiades as seen through a typical pair of binoculars. This chart will tell you whether fainter stars you identified and noted on your chart are in the sky or just in your imagination 😉

Chart 1 – Download this chart as a starting point for your observations – and to get to know the names of the Pleiads. (Atlas and Pleione are the parents of the seven sisters.)

Chart 2 – Download this chart to use for note-taking while you’re observing.

Chart 3 – Download this chart to check for faint stars you detected to see if you marked them in the right position.

Finally, compare your observation of the nebulosity with a picture of the Pleiades, such as this one.

Look North in December 2013 – seeing red yet?

That’s “red” as in garnet, for William Herschel’s Garnet Star, which is particularly well placed for observation in our northern sky in December, though it may take binoculars to bring out the color. OK, I’m getting ahead of the game. First let’s take a look at what the north sky looks like about an hour after sunset on a December evening from mid-northern latitudes.

Click image for larger chart. (Modified screenshot from Stellarium.)

Go here to download a printer-firiendly version of this chart. 

Highest of the circumpolar constellations this month is Cepheus, which I always see as a home plate – and in December, a home plate pointing roughly downward towards Polaris, the North Star. We discussed Cepheus in some detail in September. And if you’ve been following these “Look North” posts for several months you’ve also met the “W” of Cassiopeia, the “Bow” of Perseus (both to the east) and the slithering form of Draco the Dragon to the west, curling its way up, then down, and finally between the Little Dipper and the Bigger Dipper, which now is hugging the northern horizon. But what about that garnet star? Where’s that? High on our chart. Let’s zoom in on the “home plate” of Cepheus.

Click image for larger chart. (Labels added to Stellarium screenshot.)

Go here for a printer friendly version of this chart. 

Now the big question is – will this star really look red? I would say emphatically “yes!” – if seen in a telescope. “Probably,” if seen with binoculars, and “perhaps,” if seen with the naked eye. Star colors are better described as “tints.” They are very much real and relate directly to the surface temperature of a star – but they are frequently difficult for beginners to see, and I’ve met some experienced observers who swear they can’t detect color in stars.

One reason is our eyes are simply not designed for it. We see color only when the light is bright. In dim light we see in black and white. Because telescopes gather more light, it is more likely that a star seen in a telescope will show its true color. But binoculars gather a lot more light than our naked eye, so they also help significantly when trying to detect color. And in this case we’re talking about a very red star known for a couple centuries as “William Herschel’s Garnet Star.” He described it as “a very fine deep garnet color . . . .”

Looking with binoculars  I really could not detect much color with 8X40 glasses. With 10X42 I could see some. With 11X56 it clearly had a reddish tint – and with 15X70 glasses I had no doubt that I was looking at the “Garnet Star.”

OK, my font color choices in this software don’t give me garnet, so I’ve been using red in this post. But this shot of the mineral garnet really looks – at least on my computer display – hauntingly like the tint I see for Mu Cephei in my telescope. What do you see? Mu Cephei is a variable, so if you happen to catch it near its brightest, it should be easy to pick out with the naked eye. Catch it when dim and it will be down in the range of the fainter stars of the Little Dipper. Once you identify it, ponder these facts, gathered from James Kaler’s “The Hundred Greatest Stars.” Mu Cephei is:

• among the most luminous and largest stars in our galaxy
• about 2,000 light years away
• shining through lots of interstellar dust that diminishes it by about 2.5 magnitudes
• radiates 350,000 times more energy than the Sun
• has a radius that would mean that if placed in our Solar System it would engulf Mercury, Venus, the Earth, Mars, the asteroid belt, Jupiter, and reach nearly halfway to Saturn
• is in a variable stage, is unstable, losing mass, and will “surely explode someday”

Of course “someday” to astronomers could mean millions of years. Don’t go out there assuming you might catch it going out in a blaze of garnet glory! Just go out there and enjoy this wonder of the universe. Oh – and that “variable stage” means it does change in brightness in an irregular fashion going up or down about a magnitude and a half. That’s one more factor that could impact how red it looks to you – catch it near it’s peak – magnitude 3.6 – and it should look redder simply because the more light we see the easier it is to see red. near minimum it is about magnitude 5 and the changes takes place irregularly over a period of 2 – 2.5 years.

Look North in December 2012 – seeing red yet?

That’s “red” as in garnet, for William Herschel’s Garnet Star, which is particularly well placed for observation in our northern sky in December, though it may take binoculars to bring out the color. OK, I’m getting ahead of the game. First let’s take a look at what the north sky looks like about an hour after sunset on a December evening from mid-northern latitudes.

Click image for larger chart. (Modified screenshot from Stellarium.)

Go here to download a printer-firiendly version of this chart. 

Highest of the circumpolar constellations this month is Cepheus, which I always see as a home plate – and in December, a home plate pointing roughly downward towards Polaris, the North Star. We discussed Cepheus in some detail in September. And if you’ve been following these “Look North” posts for several months you’ve also met the “W” of Cassiopeia, the “Bow” of Perseus (both to the east) and the slithering form of Draco the Dragon to the west, curling its way up, then down, and finally between the Little Dipper and the Bigger Dipper, which now is hugging the northern horizon. But what about that garnet star? Where’s that? High on our chart. Let’s zoom in on the “home plate” of Cepheus.

Click image for larger chart. (Labels added to Stellarium screenshot.)

Go here for a printer friendly version of this chart. 

Now the big question is – will this star really look red? I would say emphatically “yes!” – if seen in a telescope. “Probably,” if seen with binoculars, and “perhaps,” if seen with the naked eye. Star colors are better described as “tints.” They are very much real and relate directly to the surface temperature of a star – but they are frequently difficult for beginners to see, and I’ve met some experienced observers who swear they can’t detect color in stars.

One reason is our eyes are simply not designed for it. We see color only when the light is bright. In dim light we see in black and white. Because telescopes gather more light, it is more likely that a star seen in a telescope will show its true color. But binoculars gather a lot more light than our naked eye, so they also help significantly when trying to detect color. And in this case we’re talking about a very red star known for a couple centuries as “William Herschel’s Garnet Star.” He described it as “a very fine deep garnet color . . . .”

Looking recently with binoculars  I really could not detect much color with 8X40 glasses. With 10X42 I could see some. With 11X56 it clearly had a reddish tint – and with 15X70 glasses I had no doubt that I was looking at the “Garnet Star.”

OK, my font color choices in this software don’t give me garnet, so I’ve been using red in this post. But this shot of the mineral garnet really looks – at least on my computer display – hauntingly like the tint I see for Mu Cephei in my telescope. What do you see? Mu Cephei is a variable, so if you happen to catch it near its brightest, it should be easy to pick out with the naked eye. Catch it when dim and it will be down in the range of the fainter stars of the Little Dipper. I haven’t studied it in binoculars – that’s on my observing list for this December – but Gary Seronik in his “Binocular Highlights” book says that “even in 10X30 binoculars Mu appears distinctly yellowish orange and is easy to identify in a pretty field because of that.” And once you identify it, ponder these facts, gathered from James Kaler’s “The Hundred Greatest Stars.” Mu Cephei is:

• among the most luminous and largest stars in our galaxy
• about 2,000 light years away
• shining through lots of interstellar dust that diminishes it by about 2.5 magnitudes
• radiates 350,000 times more energy than the Sun
• has a radius that would mean that if placed in our Solar System it would engulf Mercury, Venus, the Earth, Mars, the asteroid belt, Jupiter, and reach nearly halfway to Saturn
• is in a variable stage, is unstable, losing mass, and will “surely explode someday”

Of course “someday” to astronomers could mean millions of years. Don’t go out there assuming you might catch it going out in a blaze of garnet glory! Just go out there and enjoy this wonder of the universe. Oh – and that “variable stage” means it does change in brightness in an irregular fashion going up or down about a magnitude and a half. That’s one more factor that could impact how red it looks to you – catch it near it’s peak – magnitude 3.6 – and it should look redder simply because the more light we see the easier it is to see red. near minimum it is about magnitude 5 and the changes takes place irregularly over a period of 2 – 2.5 years.

Events December 2012: Mercury, Meteor Shower, Dwarf Planet, Jupiter, and more!

OK, so the meteor shower might be a snow shower, it being December and all, but we also get  an especially nice apparition of Mercury with Saturn and Venus guiding us to the elusive planet. And if that’s not enough, we have the ever reliable Winter Solstice – start beating the drums to bring the Sun back out way, please – and the King himself, Jupiter dominating an already brilliant eastern evening sky  plus a nice asteroid pass to accompany a not-quite-as-bright Dwarf Planet – you know, one of those Pluto-like things! Whew – out of breath just thinking about it all.

Here are the links to one  event at a time if you want to jump straight to the details.

• Geminid Meteor Shower – the rain of these bright little particles doesn’t get any better- December 13-14
• Mercury – an early month, early morning stage appearance with Saturn and Venus
• The Winter Solstice – Sure it happens every year but it always seems special – December 21
• Have you ever seen a Dwarf Planet? – Here’s your chance to see one (Ceres) , plus a prime member of the Asteroid Club (Vesta)
• Jupiter dominates the evening sky in the east and is with us all night

Geminid Meteor Spectacular – December 13-14

First, please meditate on this: Ask someone who is 50 miles away to strike a wooden kitchen match. Can you see it? Of course not. But that’s what’s going on when you see a meteor flash across the sky! Chances are it is from a particle about the size of the head of a kitchen match – or smaller –  and it is burning up as it hits the atmosphere above you travelling at up to 100 times faster than a rifle bullet.The result? A very, very bright “match.”

And now the Geminids – As you may know, I really don’t like that word “shower.” It builds expectations out of proportion usually, but if you have clear skies on the night of December 13-14th it’s worth digging that folding  chaise lounge out of storage, wrapping yourself in a sleeping bag – with binoculars and hot beverage handy – and staring up at those wonderful bright stars of winter waiting for some to “fall.”  Hey, if you have an Iphone or Ipad there’s an app for this – no kidding – you can record what you see and ship it off to NASA, thus contributing to scientific research –  all quite painlessly. (Go here for details.)

Oh – and this is the time of new Moon, so the Moon won’t be present to upstage the show with its bright light. The official word goes something like this – expect “about 120 meteors visible per hour for an observer at a dark sky site late on the peak night.”  That’s how Sky and Telescope puts it and those folks certainly know what they’re talking about, but in many nights of meteor watching I’ve never seen anything close to 120 per hour. When that’s the forecast I figure I have a good chance of seeing 20-30 an hour and believe me, that’s a real treat.  Maybe your skies are darker than mine, maybe your eyes are better, and maybe you’re more patient – so maybe you’ll see 120. Me – I will be delighted with a meteor every two-to-three minutes –  if not a quite a shower, that’s a  snappy snow flurry!

So where do you want to look? Up! Any part of the sky  can produce meteors, but if you trace their trails backward you will see they all emerge from the same general section of sky near Castor, the slightly dimmer Gemini twin.  Since they appear to radiate from this area of sky the most meteors will be visible when it is high overhead – and looking in that general direction is a good idea. Here’s a chart for 1:46 am ET -when Castor is at its highest – on the morning of December 14.

Click image for larger version. (Prepared from Starry Nights Pro screen shot.)

So does that mean you have to wait until  early morning to enjoy the Geminids? No! But it makes sense that if the radian point is near the eastern horizon – which it is a couple hours after sunset – then you cut your chances of seeing a meteor in half – which still means a very respectable number of meteors.  The higher the radiant point the more chance you have of seeing more meteors. But then, you can’t watch the whole sky at once – even if you have remarkably clear horizons – and one thing about meteors – they are very fast and there’s no instant replay. Blink – or be looking the wrong way – and you may hear the ooohhs and aaaahhs of companions, but you will most likely not see what they saw.

Most meteor showers are the result of the Earth passing through a trail of comet dust  – think of “Pigpen” in “Peanuts” and you get the idea of comets leaving a trail of dust. But not the Geminids. They’re something of a mystery, but the current theory is that they come from a maverick asteroid. To read all about it, go here.

Hey – why not do the observing right?  Go out about 2 am and enjoy a couple hours of meteor watching, then shift your focus to the eastern horizon where Saturnn, Venus, and eventually Mercury will put in an appearance – quite a show, really.

Mercury – an early month, early morning stage appearance with Saturn and Venus

Mercury  reaches longest elongation – distance from the Sun –  on December 4th and while it will be well-placed for another couple weeks, you need to grab the little winged messenger when you can. It pops above the horizon six times a year – three in the morning sky and three in the evening sky, but not all pops are created equal. This happens to be its best appearance for 2012.  As a bonus, brilliant Venus will act as a guide. The two planets will be closest on December 9th when you should be able to squeeze them both into the same low-power binocular field of view. But all month they will be close enough for Venus to help in finding Mercury and Saturn will be visible a bit above Venus.

Of the three, Venus will absolutely dominate in brightness at magnitude -3.9. But Mercury on December 4th will be just a tad dimmer than the brightest star we can see (roughly -0.5) and Saturn is no slouch at 0.65 – and they’re in the southeast with two bright guidepost stars, Arcturus and Spica. Here’s what to expect.

Click image for larger version. (Prepared from Starry Nights Pro screen shot.)

December 11th isn’t so shabby either because we get a crescent Moon in the picture as well, though both Venus and Mercury have dropped  down a bit, you should still be able to find them both. Venus will be easy. Mercury – well, you may want to use binoculars, though it should still be visible to the naked eye if you have clear skies – and, of course, an unobstructed eastern horizon. It’s only about half a fist above the horizon at this point.

Click image for larger version. (Created from Starry Nights Pro screen shot.)

The Winter Solstice – Sure it happens every year but it always seems special – December 21

What’s so special about the Winter Solstice? Well, for me it’s a reminder that all life – you and I, plus every animal and plant on this tiny planet depend on the Sun. The Winter Solstice – as seen from the Northern Hemisphere –  reminds me of this because on the morning of December 21 the Sun will rise as far south as it gets. In the next few days it will start inching it’s way back north and that is certainly a good sign. Sure, our seasons lag behind the sky a bit. The worst of the winter weather is yet to come. But the fact that the Sun is on its way back is certainly an encouraging sign. More primitive societies that were in better sync with the natural rhythms of the sky, celebrated this time of year and with darned good reason.

Ceres is Ceres – but you can call it a dwarf planet

“Dwarf planet” was the category astronomers agreed upon in 2006 to fit objects that are big enough to be round, but too small to have cleared the area of their orbit of other objects. That’s what Ceres is and so is Pluto, and three other known objects.  It amazed me that this rather technical decision (I have greatly over-simplified the definition) caused such a stir because it demoted Pluto from planet to dwarf planet. These are simply classifications and in astronomy over time classifications get kind of messy. I mean, stars in the 19th Century  were classified in a nice alphabetical list by their spectra – but then we kept learning more and the list got screwed around  to anything but alphabetical: OBAFGKMLT. What’s more, our Sun – and many other stars that are among the larger ones, is called a “dwarf star!” Oh my – now that sounds illogical, if not offensive.

Oh – and Ceres, the first asteroid discovered (1802) – and largest (952km) – is still often referred to as an “asteroid” because it is a dwarf planet inside the orbit of Neptune where we usually find asteroids – arghhhhhhh! See why I want to just call it Ceres and be done with the naming thing ?  😉

Do click on this for the full-size image – that’s really Vesta as imaged by Dawn, but essentially this is an artists view of what it must have looked like as the Spacecraft orbited the asteroid.  (We didn’t send anyone along in another spaceship to take pictures of the two!)

But Ceres – and even brighter Vesta – have been the subject of an extensive examination conducted by the NASA  “Dawn” spacecraft.  It has spent a year examining Vesta and is now on its was to get up close and personal with Ceres. But you can beta it to it – you can see both Cere and Vesta from your backyard this month with nothing more than binoculars, a few charts, and some determination. Of course your view will be a bit less detailed. The two will appear as stars just below naked-eye visibility. And although it’s about half the size, Vesta is the brightest because it happens to be made of – or have on it’s surface – shinier material.

This is an excellent opportunity for you to test your skill with binoculars. This month they will both look like sixth magnitude stars and thus be easily seen in binoculars – but I won’t underestimate the challenge. The good news is they are well placed near bright, familiar stars and the brilliant planet Jupiter in the evening eastern sky. That makes it easy to find the general area in which to search. The bad news is there are lots of stars up there – especially when you look with binoculars – so you need to really study the charts before you go outside, then do  very careful observing. If you find it one night, it’s  fun to look again in a few days, or even a week or two – because they do change positions rather rapidly while the stars, of course, stay put.

Go here to get a printable chart of the Path of Ceres and Vesta over the next few months.

Now print this chart to use to mark your observations of Ceres and Vesta over the same period.  It’s a chart of the same area of sky covered by the previous chart, but with the position of Ceres and Vesta shown only for December 9, 2012 as viewed from mid-northern latitudes about four hours after sunset. However, while the orientation changes somewhat by date and time, it should serve to track Ceres and Vesta for December and January. Magnitudes of a few selected objects are given in parenthesis to help identify Ceres and Vesta. Before going outside to make your observation, study the chart and determine where you think Ceres and Vesta should be that night.

And as you look at Vesta, get this picture in your mind’s eye – and as you will see at the end, Ceres look a bit different, but how different – well, we’ll see when Dawn gets there!

And here’s the best view we have of Ceres as seen by the Hubble Space Telescope.

Source: Hubblesite.org

Jupiter – let’s not forget the king of the planets

As some wag commented, our Solar Systems consist of the Sun, Jupiter, and some debris!

It is big – and only Venus outshines it, and yes, with careful viewing you can see one or more of the four Galilean moons using only binoculars. The key is to hold them steady and observe – don’t just look.  A “look” is what most people tend to do at first – that is, they hold the binoculars up and if, in 10 seconds or so, they have not seen the moons, they give up. That is not observing. To observe you need to look for at least a solid minute. That won’t guarantee you see the moons, but just taking a quick look can mean you easily miss them.

They may all be on one side of the planet and they constantly change their relationship with the planet and one another so that even with binoculars you can notice the difference over the course of a few hours. They will look like tiny stars, they will be close to the planet, and they will be roughly in a straight line that passes through the planet’s equator. This line will be pointing upward as the planet rises, level off when it’s near the mid-point of its arc across the sky, and be slanting down as it heads for the western hprizon.

The best way to prepare yourself for what to see – to check to see if you are seeing the right thing – is to go to the Sky and Telescope web site and use the javascript simulator there for your date and hour.  To do that, go here . With binoculars you want the right-side up view. With small telescopes it is much easier, of course, to see these Moons, but a telescope will change the orientation and this script allows you to change that orientation to match your telescope’s view. Here’s a typical example of what you will see.

Events December 2011 – Eclipse, Planets galore, and a very starry Christmas!

• A very starry Christmas
• Great lunar eclipse as long as you don’t live where I do ;-(
• Getting to know – I mean, really know – a planet when you see one
• Mars, Saturn, Mercury and the Moon – a morning event
• A note about meteors – not this month, but be ready in early January!
• Oh – and don’t forget Algol!

Let’s start with that very starry Christmas – I’ll be brief. If you like Christmas lore, the sky certainly cooperates this Christmas with brilliant Venus playing the role of the Christmas Star low in the southwest shortly after sunset. The sky at that time should look about like this:

Click image for larger version - Stellarium screen shot.

Click image for larger view.

And to identify what you’re seeing in the image above, click this thumbnail of the same scene.

Now – without going into great detail, suffice it to say that the Christmas Star lives in the hearts of believers,  as well as those for whom a bright star simply is a charming symbol of the season, as is a decorated tree or wreath. However, theologians and astronomers have put forth various theories over the years about what star, or comet, or combination of planets might be the “star” referenced in the Bible, and I’ve yet to encounter a single, credible explanation that makes me say – ah, that’s what it was!

But what we do have in the Christmas sky every year at this time is an asterism called the “Northern Cross.”  This is our old friend, Cygnus the Swan, who when rising in early summer appears to be flying south. Now he’s diving into the ground in the northwest and his main stars are much easier to make sense of as an upright cross asterism. The other identified stars on the chart  – Vega, Altair, and Deneb – mark the familiar “Summer Triangle,” which gets in one last shot before the wintry blasts descend on us.

And the Star of Bethlehem? Well, this year you might want to choose Venus to represent it as it begins a winter-long – and  brilliant – stand as our “evening star,” warming up the winter western sky with its shadow-casting radiance.

Great lunar eclipse as long as you don’t live where I do ;-(

My friends in Australia will have a great seat for this show on December 10-11. I won’t. Although the farther west you go in the US, the more interesting it gets, especially for early birds.

Essentially, a lunar eclipse starts with a “penumbral” eclipse, and this may give casual readers of various eclipse sites the idea that we in the east will see more than we actually will. Even on the East Coast of the US the penumbral stage of the eclipse will be underway just before the Moon sets – and that’s just half an hour before dawn.  But even under the best of conditions I find  the penumbral eclipse less than exciting – heck, I find it barely detectable. What it means is the Moon is entering the outer – dimmer – part of the Earth’s shadow. This will barely dim its light. And for us on the East Coast this will be especially difficult to notice with the Moon low in the west and us well into twilight.  So I’ve resigned myself to waiting until the next total lunar eclipse  April 14,15 of 2014 – which will be seen here.

But – elsewhere this eclipse  gets a lot more interesting. Here’s how NASA sums it up with a graphic on their eclipse web site – OK, you may need a little rocket science training to read this, but not much – be patient 😉

NASA eclipse details - see below for explanation. (You can click on this for a larger version.)

The important numbers here are in Universal Time.  To translate to your local time  go here.

The Moon enters the penumbral shadow at 11:33 Universal Time – that’s “P1” in the above graphic. For me in Massachusetts, that is 6:33 am on December 10.  For my friend John, in Oregon, that’s 3:33 am on December 10. And for my observing friends in Sydney, Australia, that’s  21:33 – 10:33 pm on December 10. See how things get better and better the farther west you go?

Unfortunately, things don’t begin to get really interesting until the umbral phase begins.  The Moon makes first contact with the dark (umbral) part of the Earth’s shadow at 12:45 UT. That’s 7:45 am for me – well after moonset and sunrise, so meaningless. Out in Oregon that’s 4:45 am, so John certainly should be able to see this phase and should see right up to the early stages of totality, though the Moon will be awfully near the horizon then – 6:06 am local time in Oregon and I imagine twilight will certainly impact the drama.

But the folks in Sydney? They get to see the whole show. Totality begins for them at 01:06 am,  Sunday December 11, 2011, with the Moon high in a dark sky.

And yes, if you haven’t figured it out by now, Europe misses this one.

If you would like to get a better handle on what’s going on – or perhaps share this experience with your kids in a meaningful way, I urge you to build my simple Earth-Moon model. I think you’ll find it fun and instructive.

Getting to know – I mean, really know – a planet when you see one

“What’s the bright star in the west right after sunset?”

I guarantee you I’ll get that question more than once in the coming months. I hope it won’t be from someone who has been reading these posts.  The truth of the matter is, we can see only five planets with our naked eye and one of those five is rare – Mercury. You have to know just when and where to look for it. But the other four are pretty darned easy to recognize on sight if you know a little about their habits and looks.

William Tyler Olcott made this clear in his wonderful  little 1907 “A Field Book of the Stars.”  Here is his short  list of rules – each of which you can put to the test any clear night this month:

If the planet is in the west, and very brilliant, it is safe to assume that it is the planet Venus.

If it is brighter than any of the fixed stars, and it is some distance from the Sun, it is doubtless the colossal Jupiter.

If it is very red it will probably be Mars.

Saturn is distinguised because of its pale, steady, yellow light.

OK, let’s  do a few “for examples.” For example, if you go out on the evening of December 26, 2011, about an hour after sunset, and look to the southwest, here’s what you should see.

Click for larger image - Stellarium screen shot.

Yep, that’s dominant Venus less than a fist away from the 2-day-old crescent Moon and both pretty near to where the Sun set an hour ago.  And when you think about it, you’re always going to see Venus somewhere relatively close to the Sun. From our perspective it swings to one side of the Sun for several months, then to the other side of it, since its orbit is closer to the Sun than ours. This coming winter it will get about as far away from the Sun as it can get, before starting to fall back towards it, so this is a good time to watch it – check on its progress from week to week.

What this means is it will frequently be an “evening star” in our western sky – BUT, though Olcott didn’t mention this – it will just as frequently be a “morning star” dominating the eastern sky before sunrise.

Mercury does the same thing – just much faster and it is doesn’t get nearly so brilliant. Last month it was in our western sky, this month it’s in the east before sunrise.

And how about Jupiter? Well, as Olcott wrote: “it is brighter than any of the fixed stars, and it is some distance from the Sun . . .” He also noted that the planets are always found in a relatively narrow arc of sky – the same one that the Sun and Moon follow – I threw the big arrow into this next screen shot to emphasize how the Moon, Venus, and Jupiter are all on the same path – that is, they are all in the plane of our solar system.

So after you locate Venus, swing your head about some to the south and look higher up. Here’s what you should see. This is for December 26, but with the exception of the Moon you should be able to see roughly the same scene any clear evening this month about 45 minutes after sunset. (OK – it will be easier to see the later in the month you look because Venus will be getting higher each night.)

Click image for larger version. This is a modified Stellarium screen shot showing a much larger area of sky than the previous one with just Venus and the Moon.

Mars, Saturn, Mercury and the Moon – a morning event

Now Mars and Saturn are a bit more problematic.  I agree with Olcott’s descriptions, but I also find it hard sometimes to distinguish between a twinkling star and a non-twinkling one that is the visual signature of a planet – and while I can readily identify star colors, they really are just tints and are not all that obvious to the unpracticed eye. Heck, I know some very experienced amateur observers who just don’t see the colors.

But to see what Olcott means, go out just about any morning this month and look to the east about an hour before sunrise.  I’ve chosen the morning of December 22 for a couple of reasons – first, the crescent Moon is in the sky and will help to guide you – and second, this happens to be the longest night of the year – the Winter Solstice, and so it’s a good time to get out and beat the drums and hope the Sun really is going to turn around again this year – stop heading south and start heading back north to chase away the winter doldrums and warm us up.

Aging Moon joins Mercury, Mars, and Saturn in the morning sky - Stellarium screen shot with labels added. Click image for larger version.

A few notes on this image: First, while Mercury is as bright as Mars, this makes it look even brighter – but it really will appear dimmer because it is so close to the horizon and in the morning twilight.  It’s about one fist away from the Moon and less than that above the horizon and will be much easier to spot if you use binoculars.  Saturn and Mars give us a lesson in color.  First, Saturn – kind of yellowish – is right next to the bluest of stars, Spica.  They both would fit in a single binocular field and Saturn is just a tad brighter.

Mars is just a bit brighter, too, and much higher – but don’t expect to see bright red. Fred Schaaf, writing in Sky and Telescope this month, says Mars plainly shows “its striking orange-yellow hue” to the naked eye this month. Yep.  Go back and forth several times between Mars, Saturn, and Spica and you should get the idea of what colors really are like in the sky. Looking at these three objects in binoculars should enhance the color a bit.

Oh – and this is the other end of that arc – the one represented by the arrow in the previous image, showing the way the planets, Sun, and Moon travel on the same path. Here the arrow should stretch from Mercury – near where the Sun will rise, to Mars. When the Sun rises, this is the general path it will follow.

A note about meteors – not this month, but be ready in early January!

The Geminids (December 13-14) are usually a great meteor shower in mid-December, but  this year the Moon will drown out all but the brightest.

However, here’s a heads-up for early January, 2012. Mark January 4, 2012, on your calendar. The rarely seem Quandrantids (I’ve caught them once and not at their best) will peak around 3 am EST on January 4. This is a shower where the peak can be spectacular – 60-200 meteors an hour– but it lasts only a couple of hours. So it’s rare to have the peak come in the early morning hours for your section of the world when the showers radiant is also at or near its highest point and when the Moon offers little or no interference.

For me a fairly bright 10-day-old Moon sets at 2:55 am – weather permitting – and it will be cold, I’m sure – I’ll start watching about 2 am and plan to stick at it until about 5 am – weather permitting.  This, by the way, is a good lesson in how “annual” astronomy events, such as the Quandrantid meteor shower, frequently become “once-in-a-lifetime” opportunities, for this will only happen if the time of the shower’s peak is just right for your location, and if the Moon isn’t interfering – and last, of course, if the local weather cooperates. That’s a lot of “ifs” and it’s why, when you get an opportunity such as this, you shouldn’t pass it up.

Oh – and don’t forget Algol!

I always check the mid-eclipse times for the coming month –  they vary depending on your location. For me the dates and times that look best are:

• 12/10/2011 @ 08:46 pm
• 12/13/2011 @ 05:35 pm
• 12/30/2011 @ 10:30 pm

That means Algol will be at its dimmest for about an hour either side of those times. To make your own checks, go to the Web calculator found here.

For more details on Algol, go here.

Look East in December 2011 – see Jupiter and take the Pleiades challenge!

 “Glitter like a swarm of firefliesTangled in a silver braid.”  – No you don’t see the Plides star cluster quite like this with your naked eye, but binoculars and small telescopes give you an awesome view. (Words from Tennyson, photo from NASA.)

The focus for those learning the stars this month is the beautiful star cluster, the Pleiades, and while charming to those with dark skies and good eyesight,  I guarantee you it will look far better in just about any binoculars you point towards it.   But in December 2011 you also have Jupiter dominating the eastern sky in early evenings – it’s the brightest “star” there – and for many parts of the world you have a total lunar eclipse on December 10. For all practical purposes the coast of Eastern North America misses this eclipse entirely – but if you live elsewhere, check out the details here – it will be especially good for those in the Pacific.

We’ll deal with the planets and lunar eclipse in more detail in a separate “events” post.   Here we’ll focus on the sky spectacular that happens every December when you look east starting about 45 minutes to an hour after sunset. Here’s what you should see.

Go here to download a printer-friendly version of this chart.

Capella, which we met last month, dominates the northeast and now it’s easy to pick out the familiar kite figure which, lead by Capella, covers the heart of the constellation Auriga. About parallel with Capella, but south of it will be the Pleiades – but don’t expect to see them well until it gets darker. You may pick them up with binoculars an hour after sunset, but to really appreciate them, wait an hour and a half after sunset.

East of the Pleiades – below it as you look at the eastern sky – is the bright guidepost star, Aldebaran. It highlights a “V” asterism that marks the head of Taurus the Bull. Dominant as it is, imagine just for a moment what it would be like if Aldebaran were our Sun. James Kaler points out that it would span 20 degrees in our sky – our Sun spans half a degree! So rising in the east, it would nearly fill the space between the Pleiades and the horizon. Get the following vision of Aldebaran in your head as you gaze to the east on a December evening.

Aldebaran, looking like the “Great Pumpkin” of Peanuts comic fame, would overwhelm us with its orange brilliance and dominate our sky if it were as close to us as our Sun. (Actually, if we were this close to Aldebaran we would be overwhelmed – charred to a crisp!)

Aldebaran is what is classified as a “giant,”  and it is indeed huge when compared to our Sun, but there are many stars much larger. It’s the 14th brightest star in our sky – compare it to Capella and you will notice that Capella is  brighter.  Aldebaran is 67 light years away – reasonably close – and in the ecliptic – the path the Sun, Moon, and planets take in our sky. This means it frequently flirts with Mars and at such times it’s fun to compare the color of these two reddish objects. It also gets occulted, from time to time, by our Moon – meaning the Moon passes in front of it. Its surface temperature is a bit lower than our Sun’s, thus the orange tint. It radiates quite a lot of its energy in infrared and is about 425 times as luminous as our Sun.

Vital stats for Aldebaran (al-DEB-ah-ran)

• Brilliance: Magnitude .85; its luminosity is the equal of 425 Suns.
• Distance: 67 light years
• Spectral Types: K5
• Position: 04:36, +16:32

Aldebaran appears to be the brightest star in another star cluster, the Hyades. In reality, it is not part of that cluster, for it’s much closer to us.  Its name – Aldebaran – means “follower” – for it appears to follow the Pleiades up the sky.  (Actually, skywatchers sometimes use the terms “precedes” and “follows” to indicate sky direction. A star that “follows” is to the east of the object it is following – and one that precedes, is to the west.)

In classical depictions of the constellations, Aldebaran is the “bull’s eye,” and  the “V” of stars near it is the bull’s head. But that V is, as mentioned ,  another open star cluster, the Hyades.

Taurus, as depicted in Uranometria (Bayer, 1603), showing Aldebran as one of his eyes. (Used with permission from the  Linda Hall Library of Science, Engineering, & Technolog.)

Hyades and Pleiades

Now what’s fun here is to pause a moment and go back and forth between the Hyades and the Pleiades. Both are open star clusters, and in reality they cover roughly the same area of space – about a dozen light years – but, you will notice immediately that the Hyades appear much larger. There’s a simple reason for that – the Hyades are just 151 light years away, while the Pleiades are more like 400 light years from us.

A careful observer will also notice that the Hyades tend to be yellowish stars, while the Pleiades are icy, blue diamonds. That’s because the Hyades at 660 million years are about ten times as old as the Pleiades. Of course, in astronomical terms both contain young stars, our Sun being about 5 billion years old and our galaxy something like 12 billion years. But the few hundred million years of age the Hyades has over the Pleiades means it does contain more yellow stars.

One more thing you might notice about the Pleiades – they look like a tiny dipper – in fact, I’ve had more than one visitor ask me if this is the “Little Dipper.” I guess you could call it The Littlest Dipper! You also could call it “Subaru.”   That’s the Japanese name  for  this little purse of celestial gemstones,  and the car maker does include them in its logo. And here are a couple of Pleiades challenges for you:

1. How many Pleiads can you see with the naked eye?

2. And can you see – with naked eye, binoculars, or telescope – the faint nebulosity that surrounds these stars?

It was that nebulosity that apparently inspired Alfred Lord Tennyson as he penned this famous tribute in “Lockesley Hall”:

Many a night I saw the Pleiades,
Rising thro’ the mellow shade,
Glitter like a swarm of fireflies
Tangled in a silver braid.

Beautiful, but no words or image can do justice to the live, real-time experience of standing outside on a crisp December evening, raising binoculars to your eyes, and seeing these icy diamonds! (Oh they can be seen with the naked eye, but binoculars give a much better view.)

Even without binoculars, the Pleiades can be quite dazzling for those with good eyes and dark skies. Not me. With my aging eyes they tend to blend together, and even when I put my glasses on I can only with care see four or five separate stars. Younger eyes do much better.

So how many stars do you see? Take your time. Patience is the key. I suggest you get a comfortable beach chair, lean back, relax, and look for at least a solid minute at a time.  How many should you see? I suspect most people who take the time to observe carefully get as many as six to 10.  Walter Scott Houston, who wrote a Sky and Telescope magazine column when astronomy was new to me in the 1950s, counted 18 with the naked eye! And the visual observer I most  admire today, Stephen James O’Meara, says in his book “The Messier Objects:”

Although largely symbolic, the age-old association of the Pleiades with the number seven remains fixed to this day – to the point that some observers swear they cannot see more than seven members, even though the Pleiades contains 10 stars brighter than 6th magnitude. Some observers question how it is possible to see 10 Pleiads in The Seven Sisters (a demonstration of the power of words . . . ) The fact is that almost three times that magic number of stars can be seen without magnification by an astute observer under dark skies.

O’Meara says he logged 17 while observing in Cambridge, MA – which hardly has dark skies.  “The trick,” he says, “is to spend a lot of time looking and plotting.” This business of “time on target” is something I find hard to convey to new observers. But it is the key. Another key is simply experience. I frequently see things that those with younger eyes don’t see, simply because I’ve seen them before and know exactly what to expect. Crossen and Tirion in their book “Binocular Astronomy” have this general piece of advice, which certainly applies here:

When I first began observing with binoculars I could not see the Rosette Nebula at all, but now it is not difficult for me even under poor sky conditions.
The most important thing in observing is to really look – a mere glance at an object or a field is simply not enough. You must keep your eye at the oculars for at least a full minute at a time.

That said, don’t let the numbers and reports by others discourage you – the Pleiades are yours to enjoy no matter how many you count.  Another noted popular astronomy author, Terrence Dickinson, writes in his book “Nightwatch,” that he has “a tough time seeing more than six stars with the unaided eye, even under excellent conditions,” but he also notes that some of his “astronomy students have reported seeing as many as 11.”

And turn binoculars on them and you should be able to easily count between 25 and 50.

The second challenge is more subtle. It involves the nebulosity that shows up in nearly every photograph of this cluster. No, don’t go looking for such a photograph. It will only prejudice you as to both the nebulosity and the fainter stars – and besides, you’ll never match a long exposure photograph with your eyes because film, or the modern CCD accumulate  much more light than our eyes.

The Pleiades, as I mentioned, are “young” stars – about 100 million years old, and in astronomical terms that means they’re mere babes. (Our star – the Sun – is about 5 billion years old. ) The Pleiades are not far removed from the cosmic womb of gas and dust in which they were formed. Until fairly recently it was assumed that this nebulosity we see was the last wispy remains of the nebulae in which the Pleiades were formed. Today it is more generally thought that this nebulosity is just a happy accident – an entirely different gossamer cloud of gas and dust that is reflecting the brilliant light of the Pleiades as they pass through it.

In any event, Tennyson seems to reference it when he refers to his “swarm of fireflies” being in a “tangled braid.“  When I look with the naked eye I certainly don’t see it. But be careful. A couple of these stars are quite bright, and because they’re close together, their light tends to blend and perhaps give the impression of being surrounded by nebulosity. Perhaps that’s all Tennyson saw, especially as the stars were near the horizon – or at least that’s where he puts them in his poem.

So while I assume Tennyson was talking about a naked eye view and perhaps glimpsed the nebulosity in pristine Victorian skies free of modern light pollution, I feel this second challenge is best pursued with binoculars and small telescopes.  While there is nebulosity near several stars, the brightest part is southeast of Merope. (Merope is identified in the downloadable charts at the end of this section.)  So I would look for this first.  What you need to do is look for a difference in the darkness of the background sky in this region. Using binoculars move away from the cluster a tad to avoid the glare – see how dark the sky is? Now move closer to it – do you detect any change in the background brightness?  Again, be careful you don’t confuse the glow around a bright star with nebulosity.

When you think you have spotted the nebulosity, it would be helpful to quickly sketch its location on the provided chart – then compare it with a picture of the Pleiades, such as this one, to see  if your impression of the location and size of the nebulosity matches what the camera reveals.

When to look

To take the challenge you want the Pleiades high in a dark – moonless – sky. In December of 2011  you’ll have to wait until about December 13 to see the Pleiades in Moonless skies at a reasonable hour.  Each night it will get better – that is, the Pleiades will be higher by the time the Moon rises and so will be seen more clearly. By the 18th the Moon isn’t rising until after midnight.  By Christmas the Moon is back in the sunset sky, but won’t offer much competition for the Pleiades until near the end of the year.

This is a good lesson, however, for looking at any faint astronomical object. When we do that we are constantly balancing these different factors of how high the object is above the horizon – the higher the better because the higher it is the less atmosphere you need to look through to see it – and where the Moon is, because it is constantly changing position and brightness, and it tends to wash out the sky anywhere near it.  But as you can see, there’s at least a two-week window when you can take the Pleiades’ challenge – assuming the weather cooperates! And, of course, the Pleiades will still be with us through the winter.

Some helpful charts

Click image for larger version. (This chart is derived from a Starry Nights Pro screen shot. A printer friendly version appears in the links at the end of this post.)

There are three printer-friendly charts listed here, but for starters I suggest you download only the first two. They both show the brightest Pleiads but the second one has no names on it and is meant for you to use – and add to – when taking either challenge. Put it on a clipboard and take it, a pencil, and a soft red light to your observing location. Then when you spot a faint star you can mark its location in relation to the brightest stars. Once you’ve done this, take a look at the third chart which shows the Pleiades as seen through a typical pair of binoculars. This chart will tell you whether fainter stars you identified and noted on your chart are in the sky or just in your imagination 😉

Chart 1 – Download this chart as a starting point for your observations – and to get to know the names of the Pleiads. (Atlas and Pleione are the parents of the seven sisters.)

Chart 2 – Download this chart to use for note-taking while you’re observing.

Chart 3 – Download this chart to check for faint stars you detected to see if you marked them in the right position.

Finally, compare your observation of the nebulosity with a picture of the Pleiades, such as this one.

Look North in December 2011 – seeing red yet?

That’s “red” as in garnet, for William Herschel’s Garnet Star, which is particularly well placed for observation in our northern sky in December, though it may take binoculars to bring out the color. OK, I’m getting ahead of the game. First let’s take a look at what the north sky looks like about an hour after sunset on a December evening from mid-northern latitudes.

Click image for larger chart. (Modified screenshot from Stellarium.)

Go here to download a printer-firiendly version of this chart. Highest of the circumpolar constellations this month is Cepheus, which I always see as a home plate – and in December, a home plate pointing roughly downward towards Polaris, the North Star. We discussed Cepheus in some detail in September. And if you’ve been following these “Look North” posts for several months you’ve also met the “W” of Cassiopeia, the “Bow” of Perseus (both to the east) and the slithering form of Draco the Dragon to the west, curling its way up, then down, and finally between the Little Dipper and the Bigger Dipper, which now is hugging the northern horizon. But what about that garnet star? Where’s that? High on our chart. Let’s zoom in on the “home plate” of Cepheus.

Click image for larger chart. (Labels added to Stellarium screenshot.)

Go here for a printer friendly version of this chart. Now the big question is – will this star really look red? I would say emphatically “yes!” – if seen in a telescope. “Probably,” if seen with binoculars, and “perhaps,” if seen with the naked eye. Star colors are better described as “tints.” They are very much real and relate directly to the surface temperature of a star – but they are frequently difficult for beginners to see, and I’ve met some experienced observers who swear they can’t detect color in stars. One reason is our eyes are simply not designed for it. We see color only when the light is bright. In dim light we see in black and white. Because telescopes gather more light, it is more likely that a star seen in a telescope will show its true color. But binoculars gather a lot more light than our naked eye, so they also help significantly when trying to detect color. And in this case we’re talking about a very red star known for a couple centuries as “William Herschel’s Garnet Star.” He described it as “a very fine deep garnet color . . . .”

Looking recently with binoculars  I really could not detect much color with 8X40 glasses. With 10X42 I could see some. With 11X56 it clearly had a reddish tint – and with 15X70 glasses i had no doubt that I was looking at the “Garnet Star.”

OK, my font color choices in this software don’t give me garnet, so I’ve been using red in this post. But this shot of the mineral garnet really looks – at least on my computer display – hauntingly like the tint I see for Mu Cephei in my telescope. What do you see? Mu Cephei is a variable, so if you happen to catch it near its brightest, it should be easy to pick out with the naked eye. Catch it when dim and it will be down in the range of the fainter stars of the Little Dipper. I haven’t studied it in binoculars – that’s on my observing list for this December – but Gary Seronik in his “Binocular Highlights” book says that “even in 10X30 binoculars Mu appears distinctly yellowish orange and is easy to identify in a pretty field because of that.” And once you identify it, ponder these facts, gathered from James Kaler’s “The Hundred Greatest Stars.” Mu Cephei is:

• among the most luminous and largest stars in our galaxy
• about 2,000 light years away
• shining through lots of interstellar dust that diminishes it by about 2.5 magnitudes
• radiates 350,000 times more energy than the Sun
• has a radius that would mean that if placed in our Solar System it would engulf Mercury, Venus, the Earth, Mars, the asteroid belt, Jupiter, and reach nearly halfway to Saturn
• is in a variable stage, is unstable, losing mass, and will “surely explode someday”

Of course “someday” to astronomers could mean millions of years. Don’t go out there assuming you might catch it going out in a blaze of garnet glory! Just go out there and enjoy this wonder of the universe. Oh – and that “variable stage” means it does change in brightness in an irregular fashion going up or down about a magnitude and a half. That’s one more factor that could impact how red it looks to you – catch it near it’s peak – magnitude 3.6 – and it should look redder simply because the more light we see the easier it is to see red. near minimum it is about magnitude 5 and the changes takes place irregularly over a period of 2 – 2.5 years.

Events December 2010: Eclipse of the Moon, Great Geminid meteors, and planets at all hours!

Lunar Eclipse Update – December 21, 2010 – 11 am EST – I fear much of the lunar eclipse reporting  – and photos –  doesn’t capture the real wonder  of what is going on – the up-the-down-escalator motion of the Moon through Earth’s shadow.

My friends Dom and Daphne from Australia, who were here observing with us in October, had a very special view of the eclipsed Moon, that does drive this home and have created a wonderful, online slideshow so we can see what they saw.  The for their view is the Moon was just emerging from totality as it rose in their eastern sky at sunset.  What make their report  special is the nearness to the eastern horizon of the Moon and the  proximity of all this to sunset so that the Earth’s shadow is actually tangible to us, along with the Belt of Venus, in the Eastern sky.

So take special note of the first shot that looks east where the shadow and the belt of Venus are.  Then watch as the Moon drops out of that shadow, diving towards the ocean – the eastern horizon. Also note the curvature of the Earth’s shadow on the moon – something that told the Greeks, long before Columbus, that the Earth was round.

What this drives home for me is that we  are seeing the shadow of the Earth darken the skynear the horizon to the east, as we always do right after sunset and – since we’re on the Earth – that shadow is huge from our perspective. Yet, out in the vicinity  of the Moon the shadow is only about 6,000 miles in diameter. At that distance, 6,000 miles would cover about a degree and a half of our sky – just three times the apparent diameter of the Moon – and so we see  the Moon appear to drop down out of that shadow – that is the Moon is moving eastward towards the horizon, while the whole show – Earth’s shadow and the Moon appear to be moving westward as the Earth turns.

Simply wonderful!  we all know the textvook explanation, but nothing beats seeing it live and the next best thing is to get a fine report of it such as the slide show Daphne put together – enjoy!

http://www.bondiblue.net/lunareclipse/eclipse.htm

 

Lunar Eclipse Update – December 21, 2010 – 7 am EST Lot’s of reports with splendid photos of the eclipse showing a very red Moon as happens when our upper atmosphere is clear can be found on today’s Spaceweather.com. Go there and explore.  Although I love to observe without aid of cameras and computers, I also loved this report and photos from Bill Williams, an amateur in Florida. Bill wrote:

“I robotically controlled my telescope (14.5-inch RCOS) and camera (Apogee U16M) remotely 307 miles away at the Chiefland Astronomy Village using the internet. I transferred the data back to Boca Raton and processed it. Is this a great hobby or what?!”

To see his pictures go here.

Lunar Eclipse Update – December 21, 2010 – 3 am EST – Bt was cloudy here in Westport, MA, but there were several Web cameras available from various locations, though most of the ones I checked were being overwhelmed by the number of people looking for a live feed showing the eclipse.

I did find the one pictured below and although it sometimes stood still, it really did give a sense of being there. Here are some screen shots of the “live” action I could see.  I should note, that while we had light snow all day, and the sky was totally overcast, before the eclipse both the sky and the night in general were very light. The full Moon shone through the clouds and bounced off the fresh snow.  By totality, however,  it was very dark – not because of heavier clouds, of course, but because the Moon wasn’t shining through the high thin overcast any more. Very dramatic change I hadn’t anticipated. Here are the screen captures of one web cast.

Click on image for larger view. In the last image of Moon the folks web casting this had changed their camera settings so it was more sensitive to the light of the eclipsed Moon.

Orrinal post on December events follows:

It’s been three years since North America was treated to a total eclipse of the Moon – and it will be more than three years until we get another chance like this! That’s a long time between lunar eclipses, so let’s put clear weather on our holiday wish list for the night of December 20/21 when there will be a terrific total eclipse!

And that’s not all – with the right weather December could be a classic month for sleep deprivation with two great early morning events, plus other cool stuff happening at more reasonable hours, so this post is divided into three parts:

• Best lunar eclipse in years! December 20/21, 2010
• A Geminids Storm! December 13/14 2010
• And Planets at all Hours – Jupiter, Uranus, Saturn – even Mercury and Venus with a cameo appearance by Mars

Best lunar eclipse in years! December 20/21, 2010

Click image for larger view.

Yep, you folks on the East Coast are reading that correctly – this is a morning event for us, but before you write it off, read on. I have a “half-is-much-more- than-50-per-cent” eclipse plan that you might want to try. The West Coast gets a break – an eclipse of the Moon happens at the same instant for everyone, but since we live in different time zones that instant occurs at different local times. So for the West Coast, the Moon turns into the Great Pumpkin just before midnight Pacific Standard Time. Oh – and if you’re on the East Coast of Australia – say Sydney? Well, you don’t miss out entirely. You get treated to the rather eerie spectacle of the Moon rising while already totally eclipsed. That will mean your first eclipse challenge will be to find the Moon! And all of this takes place in the most fabulous section of sky imaginable – right in the middle of some of the brightest constellations – Orion, Gemini, Taurus, and friends. And of course, these will be washed out by the full Moon prior to the eclipse, but during the eclipse they’ll come out in their full glory and the darkened Moon will occult a star or two as it journeys eastward. What a show! Study the map below to see if the eclipse is visible form your section of the world.

Click on image for a larger view.

And here is the eclipse sequence in Greenwich Mean Time so you can figure out how that relates to your time zone.

Click on image for larger view.

All these wonderful graphics are courtesy of Fred Espenak, www.MrEclipse.com) / CC BY-NC-ND 3.0 who has a terrific eclipse web site with lots of details about this eclipse and eclipses in general.

My half-is-much-more-than-50-per-cent plan

The real fun of an eclipse is in seeing the cover up – or uncovering – while at the same time watching the changing sky. I’m for seeing the whole show and if the weather gods cooperate, I plan to. But, I’m retired and seldom sleep more than four hours at a time, so mornings are no problem for me. Others have jobs to do and need their sleep. If that were my situation, I would try to carve out two hours and dedicate them to eclipse watching. That way I could get a real sense of the eclipse, while minimizing sleep loss. I figure if you see half of it, it’s almost as good as seeing the whole thing. So using the EST times I would make it a point to go out some time in the early evening for a few minutes just to appreciate the full Moon and note how it has washed out all but the brightest stars. Then I’d set my alarm for about 1:15 am and pop out to see the onset of the partial eclipse, which starts at 1:33 am. Again, note how the Moon is washing out most of the bright stars, even though it’s now fully into the penumbra – the weak part of the Earth’s shadow – and starting to enter the umbra. I’d stick it out to totality which begins at 2:41 am, take the next 20 minutes to enjoy the full glory of the stars with a totally eclipsed Moon, then be back to bed shortly after 3 am – thus losing about two hours sleep.

Of course you could work the same thing on the other side of the eclipse. Go to bed early and then get up about 3:15 am. If you’re out by 3:30 am, that will give you time to locate and appreciate the fully eclipsed Moon – note on the star charts below where it will be then – then watch it emerge from the Earth’s shadow starting at 3:53 am and over the next hour wash out more and more of the stars until totality ends at 5:01 am.

Or the-heck-with-sleep-plan, bring on the show!

Hey – one complete total eclipse in nearly six years – are you really going to let a little sleep deprivation steal the show? I’m not. This eclipse has me really psyched for several reasons. First, this is a real dry period between eclipses. There is one next June 15, but North America misses that one entirely. Next December (December 10, 2011) there’s another, and this one can be seen in part by those on the West Coast of North America. But the next full show for all of North America is not until April 14-15, 2014.

Another thing I like about this eclipse is it comes near the time of the winter solstice – 6:38pm, December 21,2010 – and that means the full Moon will be very high in our sky. The full Moon always rises opposite the Sun – so as the winter Sun sets in the southwest, the full Moon will rise in the northeast and travel high overhead.

A third thing I like is where, exactly, in the sky the Moon will be – it’s right in the middle of the Winter Hexagon – an area of sky that includes some of the brightest stars we see and most dramatic asterisms. In fact, the constellation that nearly everyone knows is Orion, and on eclipse night it’s going to look like Orion’s balancing the Moon on the end of his raised club! No kidding. Maybe we should think of that club as a torch for this night. Take a look!

Here's the Moon poised near the end of Orion's club just before the eclipse begins. Of course the Moon will drown out all but the brightest stars in Orion, but once totality begins most of these stars should be visible. (Starry Nights Pro screenshot.)

Is that cool? But wait, there’s more!

I admit I can’t spend hours looking at an eclipsed Moon – especially when there are so many other things to see in the surrounding sky. So by all means, bring your binoculars or a small telescope to this event. I’ll be using a telescope, but here I’ll stick to describing the naked eye and binocular sights.

Winter Hexagon and other things to look for as the moon gets darker and the stars come out. (Modified Starry Nights Pro screenshot.)

Click here for a printer-friendly version of the above chart.

The Winter Hexagon is a wonderful region of night sky, alive with a wide variety of sights. The stars that form it are among the brightest, starting with Sirius, the brightest star in the northern celestial hemisphere and at 8 light years, one of our closest companions. Procyon plays the “Little Dog” to the Sirius “Big Dog” – Sirius is the brightest star in Canis Major, Procyon the brightest star in Canis Minor. Castor and Pollux, the heavenly twins, anchor the next corner of the hexagon; then comes brilliant Capella, followed by the orange-tinted Aldebaran – the “bull’s eye” – and finally, the icy blue star at Orion’s left foot, Rigel. The best binocular sites in this area start with the Pleiades star cluster and its close neighbor, the Hyades cluster. (See the “look east” post for December for more about these two.) Orion’s Belt – the three bright stars in a row – slashes across the celestial equator and also is a wonderful, star-rich area to explore with binoculars. Finally, there’s the Great Orion Nebula – M42 – in the giant’s sword that hangs below his belt. Binoculars will show a little cloud in the middle of the sword that is an incredible region of gas and dust where stars are being born. Of course to see all this at its best you need to wait for totality at 2:41 am.

With binoculars or telescope

Obviously you can look at mountains, craters, and seas on the Moon and watch as they each get caught in the Earth’s shadow. But what I think will be most fun is to note the eastward motion of the moon by looking at its leading edge – the dark edge – and watch as one star after another gets snuffed out by the Moon. Now these stars will be more difficult to see during the partial phase, but the darker the moon gets, the easier it will be to see this happen and thus get a real sense that the Moon is indeed traveling around us. The Moon, like everything else in the sky, will appear to move from east to west. But at the same time, its motion around the Earth causes it to move eastward against the backdrop of distant stars. Once totally eclipsed, these “occultations” should be very easy to see.

The following video is a simulation made with Starry Nights Pro software. It shows the view from my location at 42 degrees north. Your view of the Moon – and which stars it occults – will depend on your latitude -so unless you’re within about 10 degrees of me either direction, you should take this simulation as illustrating what to expect in general, but the specific stars will differ. The brightest star occulted near the start is magnitude 7 HIP27698 – which should be visible in binoculars, if not at the start, certainly later when it pops out of the other side from behind a fully eclipsed Moon. The dimmest shown are about magnitude 12 and only visible in telescopes of the size most amateur astronomers use.

Oh – and if you stay up until the end of the eclipse, be sure to take a look at Saturn about 30 degrees high in the southeast and just five degrees from the beautiful double star Porrima. As always, it’s a grand show in any size telescope and now its rings are well displayed – the last couple of years they haven’t been. Below and to the left, Venus will be about six degrees above the eastern horizon and outshining everything except the Moon. Porrima, by the way, is an exquisite, but challenging double for small telescopes that’s getting a little easier to split every month as the two nearly identical stars move farther apart in their orbits.

A Geminids Storm! December 13/14 2010

This could be the best meteor shower of the year, especially for residents on the East Coast of North America – though it should be very good across the country.

The Geminids weren’t discovered until 1862, and when they were, they were more a meteor sprinkle, than a meteor shower. In 1877 astronomers were recording about 14 per hour. That’s wimpy. The Zenith Hourly Rate (ZHR) for the Perseids is 120. But a funny thing happened on the way to 2010 – the Geminids just kept getting better. In the 1930s the rate climbed to 50, was 60 per hour in the next two decades, and about 80 for the remainder of the century. But the respected “Observer’s Handbook 2010” of the Royal Astronomical Society of Canada puts the rate for this year at 120 – tied with the Perseids – and some say it could go higher!

Now before you get salivating to go out on a cold December night and lie in a lounge chair, let me set the record straight on “zenith hourly rate.” This is the number that’s usually quoted in various accounts – but most of the time this rate is mentioned it’s not explained and it leaves too many people with false hopes – especially those living in light-polluted areas, which is most of us. This rate is for ideal conditions, and I’ve never been lucky enough to have those ideal conditions. I would be tickled pink if I averaged one meteor per minute from a very dark site – the best I can do near home. Here’s how ZHR is defined in the Handbook:

Zenith Hourly Rate (ZHR) defined as the number of meteors a single average observer would see if the radiant were directly overhead and the sky dark and transparent with a limiting stellar magnitude of +6.5 (conditions that are rarely met in reality.)

That last phrase could also be written as “never in my lifetime!” 😉 I consider my skies super when the limiting magnitude is 5.5. Now I’m not a dedicated meteor shower watcher – but I’ve certainly been out there many nights over the years and generally have had very enjoyable meteor observing sessions – but seldom anything like what people report from the rare ideal site. But then – to have all the astronomical conditions just right is rare enough – yet that’s what this year’s Geminids could deliver, particularly for folks in the eastern half of the country. (As you move west there will be more interference from the Moon at the predicted shower peak time, but the Geminids still should put on a terrific display. The Moon will be low and just past first quarter.)

Oh – and for the radiant of this shower to be directly overhead here? The radiant – the general area where the meteors appear to radiate from – is a point less than two degrees from the bright star Castor and will be as high as it gets in my sky at 2:42 am EST. That won’t be directly overhead – but it’s at about 79 degrees altitude which is close enough to call directly overhead. (Use the Winter Hexagon chart posted above to find Castor – it’s the bright star near the top and is identified in that chart.)

Now here’s the really great news – and it’s why if the weather is clear I will be out there from 1 am on watching for Geminids. The quarter moon – which won’t interfere too much with earlier observing, sets at 1:16 am EST locally. AND – the Geminids are forecast to reach their peak at about 2 am EST. Now these forecasts are seldom right on, but they’re usually good. And I still have fond memories of a Leonid shower near the start of this century which really was a shower – the best I’ve seen in my life. And I hope to top that with this year’s Geminids.

But if the early morning peak turns you off, don’t give up on observing the Geminids. Start observing about four or five hours after sunset and you still should see enough to make it worth your while.

Where to look? They can appear anywhere. But more will be nearer the radiant. During my observing time I plan to be lying flat on my back and looking straight up. And by the way – that one or two a minute? That’s an “average.” Don’t expect to see one or two every minute. You have to look up continuously. And while you can talk to a friend, don’t let your eyes drift from the sky. Do that for at least 30 minutes and you should come close to the average – which I hope will be about one a minute. And I would be real happy with one every couple of minutes.

Finally, if you do see any, note their color – Geminids can be any of several colors – and, of course, notice how the meteor traces back to the radiant point in the sky in the constellation of Gemini. If you see a particularly bright one – take your binoculars and look where it just flashed. You ‘ll have a good chance of seeing a trail, similar to the vapor trail of a jet.

One last note: I think of most meteor showers as comet dust. That is, the Earth is passing through the dusty remnants left by a comet as it got near the Sun. But the Geminids are a bit of a puzzle here. They are believed to be associated with an asteroid known as 3200 Phaethon – only some folks feel this is not an ordinary asteroid. In fact, it is a dead comet. The jury is still out – but whatever the source, it should sprinkle some pixie dust our way December 13/14, and I hope to catch my share.

And Planets at all Hours – Jupiter, Uranus, Saturn – even Mercury and Venus, with a cameo appearance by Mars

Planet-wise, the month starts out with a bang. Jupiter and Uranus are high to the south at sunset; Saturn is getting higher and higher in the pre-dawn sky; and on December 2 there’s a terrific little triangle about an hour before sunrise of the crescent Moon, brilliant Venus, and the guidepost star, Spica. meanwhile, off to the north is another bright guidepost star, Arcturus, and Saturn is well placed above the triangle. (The Moon has a similar conjunction with Venus in the pre-dawn sky of December 31.)

Click image for larger version. (Starry Nights Pro screenshot with labels added.)

Click here to download a printer-friendly version of this chart.

Binocular users can bag Uranus, the planet that about doubled the size of our solar system – the “Georgian Star.” (To learn more about Uranus, see the September post here.) Uranus can be seen with binoculars, assuming it’s well placed, any time – but it’s far easier to locate when it is right near a bright planet such as Jupiter. This is the third time this year it has come close to Jupiter, but don’t hold your breath for this to happen again soon! In other words, see it now! (Neptune went through a similar sequence last year – now it’s off to the southwest and harder to find, though if you want to look, there’s a finder chart at the Sky and Telescope Web site.)

Jupiter joins the party!

Uranus starts off the month about three degrees from Jupiter in a neat little triangle with two stars that are almost identical in brightness to the planet, which is magnitude 5.9 – 20 Piscium (5.5) and 24 Piscium (5.9). As the month goes on, Jupiter moves closer and closer until the end of the month when it’s actually inside this little triangle and less than a degree from Uranus. Here are some charts to help you pick out the distant planet from the much more distant stars that form a backdrop. The circle covers five degrees, a typical binocular field of view, though your binoculars may show more.

Click image for larger version. (Starry Nights Pro screenshot with labels added.)

Click here to download a printer-friendly version of the above chart.

Click image for larger version. (Starry Nights Pro screenshot with labels added.)

Click here to download a printer-friendly version of the above chart.

Click image for larger version. (Starry Nights Pro screenshot with labels added.)

Click here to download a printer-friendly version of the above chart.

The Mars/Mercury Challenge

Can you find these two planets in the bright twilight using binoculars? On December 13 if you have a location with a clear western horizon – and really clear skies, you can put this to the test. It’s detailed by Tony Flanders in Sky and Telescope for December. He suggests looking just after sunset, but he thinks the easiest time to spot them will come about half an hour after sunset. This is one of those familiar races where to see the object, you need a dark sky behind it, but as the sky gets darker, the objects gets closer to the horizon making it more difficult to see.

Actually, your success will really depend on the weather. Looking in the right place should be easy. At my latitude of 42 degrees north the Sun will set that day at azimuth 239 degrees – pretty much southwest. Half an hour later Mercury and Mars will be at azimuth 234 degrees – five degrees to the south of where the Sun set. So if it’s clear, I plan to watch the Sun set and note the spot on the horizon where it vanishes. I’ll give it about 10 minutes, then start scanning about one binocular field to the south of that spot. In 30 minutes Mars and Mercury should still be roughly three degrees above the horizon. So if I look one binocular field to the south of where the sun set and just above the horizon, my binoculars should show me two first magnitude “stars” – it should look like this.

Labels added to Starry Nights Pro screenshot.

Look East in December 2010: Seven sisters and so much more !

Click image for much larger view. (Modified from Starry Nights Pro screenshot.)

The focus for those learning the stars this month is the beautiful star cluster, the Pleiades – known in many cultures as the “Seven Sisters.” But in December 2010 there’s also a great lunar eclipse; the Geminids should put on a terrific meteor show; and the planets promise several “cool” appearances.

For details on the eclipse, Geminids, and planet show, be sure to see the December 2010 Events post. Here we’ll focus on the sky spectacular that happens every December when you look east starting about 45 minutes after sunset. Here’s what you should see.

Go here to download a printer-friendly version of this chart.

Capella, which we met last month, dominates the northeast and now it’s easy to pick out the familiar kite figure which, lead by Capella, covers the heart of the constellation Auriga. About parallel with Capella, but south of it will be the Pleiades – but don’t expect to see them well until it gets darker. You may pick them up with binoculars an hour after sunset, but to really appreciate them, wait an hour and a half after sunset.

East of the Pleiades – below it as you look at the eastern sky – is the bright guidepost star, Aldebaran. It highlights a “V” asterism that marks the head of Taurus the Bull. Dominant as it is, imagine just for a moment what it would like if Aldebaran were our Sun. James Kaler points out that it would span 20 degrees in our sky – our Sun spans half a degree! So rising in the east, it would nearly fill the space between the Pleiades and the horizon. Get the following vision of Aldebaran in your head as you gaze to the east on a December evening.

Aldebaran, looking like the "Great Pumpkin" of Peanuts comic fame, would overwhelm us with its orange brilliance and dominate our sky. (Actually, if we were this close to Aldebaran we would be overwhelmed - charred to a crisp!)

Aldebaran is what is classified as a “giant,”  and it is indeed huge when compared to our Sun, but there are many stars much larger. It’s the 14th brightest star in our sky – compare it to Capella and you will notice that Capella is  brighter.  Aldebaran is 67 light years away – reasonably close – and in the ecliptic – the path the Sun, Moon, and planets take in our sky. This means it frequently flirts with Mars and it’s fun to compare the color of these two reddish objects. It also gets occulted, from time to time, by our Moon – meaning the Moon passes in front of it. Its surface temperature is a bit lower than our Sun’s, thus the orange tint. It radiates quite a lot of its energy in infrared and is about 425 times as luminous as our Sun.

Vital stats for Aldebaran (al-DEB-ah-ran)

• Brilliance: Magnitude .85; its luminosity is the equal of 425 Suns.
• Distance: 67 light years
• Spectral Types: K5
• Position: 04:36, +16:32

Aldebaran appears to be the brightest star in another star cluster, the Hyades. In reality, it is not part of that cluster, for it’s much closer to us.  Its name – Aldebaran – means “follower” – for it appears to follow the Pleiades up the sky.  (Actually, skywatchers sometimes use the terms “precedes” and “follows” to indicate sky direction. A star that “follows” is to the east of the object it is following – and one that precedes, is to the west.)

In classical depictions of the constellations, Aldebaran is the “bull’s eye,” and  the “V” of stars near it is the bull’s head. But that V is, as mentioned ,  another open star cluster, the Hyades.

Taurus, as depicted in Uranometria (Bayer, 1603), showing Aldebran as one of his eyes. (Used with permission from the  Linda Hall Library of Science, Engineering, & Technolog.)

Hyades and Pleiades

Now what’s fun here is to pause a moment and go back and forth between the Hyades and the Pleiades. Both are open star clusters, and in reality they cover roughly the same area of space – about a dozen light years – but, you will notice immediately that the Hyades appear much larger. There’s a simple reason for that – the Hyades are just 151 light years away, while the Pleiades are more like 400 light years from us.

A careful observer will also notice that the Hyades tend to be yellowish stars, while the Pleiades are icy, blue diamonds. That’s because the Hyades at 660 million years are about ten times as old as the Pleiades. Of course, in astronomical terms both contain young stars, our Sun being about 5 billion years old and our galaxy something like 12 billion years. But the older Hyades does contain more yellow stars.

One more thing you might notice about the Pleiades – they look like a tiny dipper – in fact, I’ve had more than one visitor ask me if this is the “Little Dipper.” I guess you could call it The Littlest Dipper! You also could call it “Subaru.”   That’s the Japanese name  for  this little purse of celestial gemstones,  and the car maker does include them in its logo. And here are a couple of Pleiades challenges for you:

1. How many Pleiads can you see with the naked eye?

2. And can you see – with naked eye, binoculars, or telescope – the faint nebulosity that surrounds these stars?

It was that nebulosity that apparently inspired Alfred Lord Tennyson as he penned this famous tribute in “Lockesley Hall”:

Many a night I saw the Pleiades,
Rising thro’ the mellow shade,
Glitter like a swarm of fireflies
Tangled in a silver braid.

Beautiful, but no words or image can do justice to the live, real-time experience of standing outside on a crisp December evening, raising binoculars to your eyes, and seeing these icy diamonds! (Oh they can be seen with the naked eye, but binoculars give a much better view.)

Even without binoculars, the Pleiades can be quite dazzling for those with good eyes and dark skies. Not me. With my aging eyes they tend to blend together, and even when I put my glasses on I can only with care see four or five separate stars. Younger eyes do much better.

So how many stars do you see? Take your time. Patience is the key. I suggest you get a comfortable beach chair, lean back, relax, and look for at least a solid minute at a time.  How many should you see? I suspect most people who take the time to observe carefully get as many as six to 10.  Walter Scott Houston, who wrote a Sky and Telescope magazine column when astronomy was new to me in the 1950s, counted 18 with the naked eye! And the visual observer I most  admire today, Stephen James O’Meara, says in his book “The Messier Objects:”

Although largely symbolic, the age-old association of the Pleiades with the number seven remains fixed to this day – to the point that some observers swear they cannot see more than seven members, even though the Pleiades contains 10 stars brighter than 6th magnitude. Some observers question how it is possible to see 10 Pleiads in The Seven Sisters (a demonstration of the power of words . . . ) The fact is that almost three times that magic number of stars can be seen without magnification by an astute observer under dark skies.

O’Meara says he logged 17 while observing in Cambridge, MA – which hardly has dark skies.  “The trick,” he says, “is to spend a lot of time looking and plotting.” This business of “time on target” is something I find hard to convey to new observers. But it is the key. Another key is simply experience. I frequently see things that those with younger eyes don’t see, simply because I’ve seen them before and know exactly what to expect. Crossen and Tirion in their book “Binocular Astronomy” have this general piece of advice, which certainly applies here:

When I first began observing with binoculars I could not see the Rosette Nebula at all, but now it is not difficult for me even under poor sky conditions.
The most important thing in observing is to really look – a mere glance at an object or a field is simply not enough. You must keep your eye at the oculars for at least a full minute at a time.

That said, don’t let the numbers and reports by others discourage you – the Pleiades are yours to enjoy no matter how many you count.  Another noted popular astronomy author, Terrence Dickinson, writes in his book “Nightwatch,” that he has “a tough time seeing more than six stars with the unaided eye, even under excellent conditions,” but he also notes that some of his “astronomy students have reported seeing as many as 11.”

And turn binoculars on them and you should be able to easily count between 25 and 50.

The second challenge is more subtle. It involves the nebulosity that shows up in nearly every photograph of this cluster. No, don’t go looking for such a photograph. It will only prejudice you as to both the nebulosity and the fainter stars – and besides, you’ll never match a long exposure photograph with your eyes because film, or the modern CCD accumulate  much more light than our eyes.

The Pleiades, as I mentioned, are “young” stars – about 100 million years old, and in astronomical terms that means they’re mere babes. (Our star – the Sun – is about 5 billion years old. ) The Pleiades are not far removed from the cosmic womb of gas and dust in which they were formed. Until fairly recently it was assumed that this nebulosity we see was the last wispy remains of the nebulae in which the Pleiades were formed. Today it is more generally thought that this nebulosity is just a happy accident – an entirely different gossamer cloud of gas and dust that is reflecting the brilliant light of the Pleiades as they pass through it.

In any event, Tennyson seems to reference it when he refers to his “swarm of fireflies” being in a “tangled braid.“  When I look with the naked eye I certainly don’t see it. But be careful. A couple of these stars are quite bright, and because they’re close together, their light tends to blend and perhaps give the impression of being surrounded by nebulosity. Perhaps that’s all Tennyson saw, especially as the stars were near the horizon – or at least that’s where he puts them in his poem.

So while I assume Tennyson was talking about a naked eye view and perhaps glimpsed the nebulosity in pristine Victorian skies free of modern light pollution, I feel this second challenge is best pursued with binoculars and small telescopes.  While there is nebulosity near several stars, the brightest part is southeast of Merope. (Merope is identified in the downloadable charts at the end of this section.)  So I would look for this first.  What you need to do is look for a difference in the darkness of the background sky in this region. Using binoculars move away from the cluster a tad to avoid the glare – see how dark the sky is? Now move closer to it – do you detect any change in the background brightness?  Again, be careful you don’t confuse the glow around a bright star with nebulosity.

When you think you have spotted the nebulosity, it would be helpful to quickly sketch its location on the provided chart – then compare it with a picture of the Pleiades, such as this one, to see  if your impression of the location and size of the nebulosity matches what the camera reveals.

When to look

To take the challenge you want the Pleiades high in a dark – moonless – sky. In December of 2010 both the first and last weeks give good, Moonless skies at a reasonable hour. At the start of the month the Moon is in the early morning sky. It’s new on December 5 and won’t start to be a problem until around the 10th. By Christmas the Moon isn’t rising until five hours after sunset, and it rises later each night through the end of the month. The Pleiades will be well up about two and a half hours after sunset.

This is a good lesson, however, for looking at any faint astronomical object. When we do that we are constantly balancing these different factors of how high the object is above the horizon – the higher the better because the higher it is the less atmosphere you need to look through to see it – and where the Moon is, because it is constantly changing position and brightness, and it tends to wash out the sky anywhere near it.  But as you can see, there’s at least a two-week window when you can take the Pleiades’ challenge – assuming the weather cooperates! And, of course, the Pleiades will still be with us through the winter.

Some helpful charts

Click image for larger version. (This chart is derived from a Starry Nights Pro screen shot. A printer friendly version appears in the links at the end of this post.)

There are three printer-friendly charts listed here, but for starters I suggest you download only the first two. They both show the brightest Pleiads but the second one has no names on it and is meant for you to use – and add to – when taking either challenge. Put it on a clipboard and take it, a pencil, and a soft red light to your observing location. Then when you spot something you can mark its location in relation to the brightest stars. Once you’ve done this, take a look at the third chart which shows the Pleiades as seen through a typical pair of binoculars. This chart will tell you whether fainter stars you identified and noted on your chart are in the sky or just in your imagination 😉

Chart 1 – Download this chart as a starting point for your observations – and to get to know the names of the Pleiads. (Atlas and Pleione are the parents of the seven sisters.)

Chart 2 – Download this chart to use for note-taking while you’re observing.

Chart 3 – Download this chart to check for faint stars you detected to see if you marked them in the right position.

Finally, compare your observation of the nebulosity with a picture of the Pleiades, such as this one.

Look North in December – Seeing RED yet?

That’s “red” as in garnet, for William Herschel’s Garnet Star, which is particularly well placed for observation in our northern sky in December, though it may take binoculars to bring out the color. OK, I’m getting ahead of the game. First let’s take a look at what the north sky looks like about an hour after sunset on a December evening from mid-northern latitudes.

Click image for larger chart. (Modified screenshot from Stellarium.)

Go here to download a printer-firiendly version of this chart. Highest of the circumpolar constellations this month is Cepheus, which I always see as a home plate – and in December, a home plate pointing roughly downward towards Polaris, the North Star. We discussed Cepheus in some detail in September. And if you’ve been following these “Look North” posts for several months you’ve also met the “W” of Cassiopeia, the “Bow” of Perseus (both to the east) and the slithering form of Draco the Dragon to the west, curling its way up, then down, and finally between the Little Dipper and the Bigger Dipper, which now is hugging the northern horizon. But what about that garnet star? Where’s that? High on our chart. Let’s zoom in on the “home plate” of Cepheus.

Click image for larger chart. (Labels added to Stellarium screenshot.)

Go here for a printer friendly version of this chart. Now the big question is – will this star really look red? I would say emphatically “yes!” – if seen in a telescope. “Probably,” if seen with binoculars, and “perhaps,” if seen with the naked eye. Star colors are better described as “tints.” They are very much real and relate directly to the surface temperature of a star – but they are frequently difficult for beginners to see, and I’ve met some experienced observers who swear they can’t detect color in stars. One reason is our eyes are simply not designed for it. We see color only when the light is bright. In dim light we see in black and white. Because telescopes gather more light, it is more likely that a star seen in a telescope will show its true color. But binoculars gather a lot more light than our naked eye, so they also help significantly when trying to detect color. And in this case we’re talking about a very red star known for a couple centuries as “William Herschel’s Garnet Star.” He described it as “a very fine deep garnet color . . . .” OK, my font color choices in this software don’t give me garnet, so I’ve been using red in this post. But this shot of the mineral garnet really looks – at least on my computer display – hauntingly like the tint I see for Mu Cephei in my telescope. What do you see? Mu Cephei is a variable, so if you happen to catch it near its brightest, it should be easy to pick out with the naked eye. Catch it when dim and it will be down in the range of the fainter stars of the Little Dipper. I haven’t studied it in binoculars – that’s on my observing list for this December – but Gary Seronik in his “Binocular Highlights” book says that “even in 10X30 binoculars Mu appears distinctly yellowish orange and is easy to identify in a pretty field because of that.” And once you identify it, ponder these facts, gathered from James Kaler’s “The Hundred Greatest Stars.” Mu Cephei is:

• among the most luminous and largest stars in our galaxy
• about 2,000 light years away
• shining through lots of interstellar dust that diminishes it by about 2.5 magnitudes
• radiates 350,000 times more energy than the Sun
• has a radius that would mean that if placed in our Solar System it would engulf Mercury, Venus, the Earth, Mars, the asteroid belt, Jupiter, and reach nearly halfway to Saturn
• is in a variable stage, is unstable, losing mass, and will “surely explode someday”

Of course “someday” to astronomers could mean millions of years. Don’t go out there assuming you might catch it going out in a blaze of garnet glory! Just go out there and enjoy this wonder of the universe.