or maybe this:

or perhaps this?

It all depends, of course, on your imagination, but for me I see something like the last image. Even that doesn’t quite capture what my imagination wants to do with these stars. What I see is a huge and rather grumpy bear, emerging from his cave a bit early after hibernating through a few rough months, and now he’s stretching – and clawing – his way up my sky, and he is magnificent!
But I admit, for years it wasn’t that way. I saw instead what I suspect many people see – the Big Dipper rising. And I knew, sort of vaguely, that this asterism – one of the most familiar in the world – was a major portion of the constellation of the Great Bear, Ursa Major.  But really, large as the Dipper is, it’s just the hind quarter of the Big Bear, which is really large, and when I finally took the time to trace out his head and ears and front and rear paws, he quickly became one of my favorite constellations – one of the rare ones like Orion and Scorpius that really look like what they depict.  And funny – I can’t explain why, but I seldom see it as a bear except at this time of year when it is rising. Then it seems to dominate my northern sky and my imagination.

Oh – did I say it looks like a bear? No – I should have said it looks like a bear no one has seen except in the sky – a bear with a long tail! I don’t know why that is. I assume it is because of the second depiction, which is how Johann Bayer pictured the Great Bear in his “Uranometria,” a breakthrough star atlas published in 1603.  Bayer was a lawyer, not a hunter. Maybe he had never seen a bear?

The first depiction, a Stellarium screenshot, is the best one to use as a guide for finding the correct stars. Besides the Dipper stars, there are a dozen more that trace out his main features, and all of these are either third magnitude, or on the brighter side of fourth magnitude – that is between 3.5 and 4, so they should be visible from most locations – assuming, of course, you are in mid-northern latitudes.  The chart that follows gives a view of the Bear in context with the rest of the northern sky in February.

About one hour after sunset, look north and you should see a sky similar to the one shown in our chart below. The height of Polaris, the North Star, will be the same as your latitude. Polaris stays put.  Everything else appears to rotate about it, so our view of all else changes in the course of the evening – and from night to night. It’s a good idea to check the north sky every time you observe to get a sense of how things are changing and to orient yourself.  Notice that the “W” now looks more like an “M” as it starts to roll on down into the northwest.

Look carefully at that photo, then compare it with this star chart which is what we see from mid-northern latitudes as as we look southeast early on a February evening.

For a printer-friendly version of this chart, click here.

People in the north tend to think that the stars are brighter in winter because the air is so cool and crisp. That certainly could be a factor. But the simple fact is our winter sky is dominated by a whole lot of very bright stars. In fact, there are 22 stars of first magnitude – 16 of which are visible from the northern hemisphere and more than half of these are visible in “prime time” on a February evening. And nearly all these bright stars are jammed into a space taking up less than one-quarter of the February night sky – that’s just one-eighth of the total night sky we can see through the year! Add to that the seven bright stars of the Big Dipper being dragged up the northeastern sky by the Great Bear on a February evening, and it is no wonder that in the dead of a northern winter our skies offer a lively, colorful, star-spangled spectacular.

The Hexagon alone contains seven of the first magnitude stars in our sky and an eighth that is the brightest second magnitude star we see – in other words, that one just misses being first magnitude by a hair. And nearby is Adhara, a star that sits right on the border between second and first magnitude; plus Regulus, another first magnitude star, is rising in the east. Whew! That’s a lot. Let’s review.  Going  counterclockwise and starting at the bottom, the Hexagon’s corners are marked by:

• Sirius, the brightest, and at about eight light years one of the closest, stars in our sky – except the Sun, of course.
• Rigel, the blue giant that marks one of Orion’s feet.
• Aldebaran, the brilliant orange star that is the eye of Taurus the Bull and dominates the nearest open star cluster, the Hyades.
• Capella, now high overhead, is really a complex of four stars that we see as one.
• Castor and Pollux, the twins, one of which (Pollux) is first magnitude, while Castor is the brightest second magnitude star we see.
• Procyon, the “Little Dog” star, which is dim only in comparison to Sirius, the “Big Dog.”

And . . .

• Inside the Hexagon is another first magnitude star, Betelgeuse, the red giant that marks Orion’s shoulder, not to mention the three bright stars of Orion’s Belt - all second magnitude.
• Regulus, the “Little King,” is a first magnitude star that is rising in the east and bringing us the familiar sickle of bright stars that mark the head of the lion. We’ll study it closely next month.
• Adhara is the western-most star of the distinctive small triangle of stars beneath Sirius. At magnitude 1.5 I call it a first magnitude star, but others consider this second magnitude. So depending on how you count Adhara there are either 21 or 22 first magnitude stars.

Before leaving the Winter Hexagon, I must stress that  this is not simply a northern hemisphere show - if you live  in Sydney, Australia, you could just rename this the “Summer Hexagon.” I see these stars in the southeast – my friends in Sydney see them in the northeast of their sky – and, of course, since they’re “standing on their heads,” they see them a bit differently – something like this!

February Guidepost Stars

Of the stars mentioned so far, the two dog stars, Sirius and Procyon, plus the fence sitter, Adhara, are the guidepost stars to learn this month. They are the ones you can spot near the southeastern horizon, coming into view about 45 minutes to an hour after sunset. (We’ll have more to say about Regulus next month, and the other stars mentioned we’ve met in previous months.) To see the February guidepost stars – and the asterism of the Virgins -  look low in the southeast about 45 minutes to an hour after sunset.  Here’s what you should see.

For a printer-friendly version of this chart, click here. Procyon, the seventh brightest star we see, is first up in our sky, and thus the highest, of these three. To the southeast and a tad lower is brilliant Sirius, brightest star in our sky, and next to the North Star, Polaris, probably the best known star in the world. Adhara is the brightest star in the  “Virgins,” a simple,  distinctive  triangle asterism. But, of course, Sirius is dominant – far brighter than any other star we see in our night sky. I always think of Sirius as the eye of the great dog and as he sits, the triangle seems to be his rear haunches. From our perspective Adhara may be just another bright star, but of these three it is really the brightest by far – it’s just much farther away than the other two.  If we compared them side by side we would find that Procyon shines with the light of seven Suns, Sirius 23, and Adhara has a luminosity to the eye of 3,700 Suns! Now that’s bright.  And in another way, Adhara reveals our human bias, for if we had ultraviolet vision Adhara would be the brightest star in our sky, not Sirius. But again – that not the way we see it. From our perspective Sirius and Procyon are very bright because they are very close to Earth. Sirius, at a little more than eight light years is the closest star that we in the mid-northern latitudes see in our night sky. Procyon, at about 11 light years, is fourteenth on the list of nearest stars.  Most of the stars that are nearer than Procyon are also much fainter – in fact, too faint to see with the naked eye. If we count just those stars bright enough to see with the naked eye, Procyon is the sixth closest and Sirius is the second closest.  (The closest star, Alpha Centauri, is visible only to those in, or near, the Southern Hemisphere.) But Adhara? Adhara is 405  light years away – about the same distance as the North Star, Polaris. Sirius will frequently seem to be changing colors, but that’s just the effect of our atmosphere. Just as our atmosphere makes our Sun look red when it is rising or setting, it makes any bright star near the horizon appear to dance and change colors rapidly.

Sirius is known as a “dog star” because it is the brightest star of the classic constellation, Canis Major – the Big Dog. Procyon is the brightest star in the constellation Canis Minor, the Little Dog. When you look at these constellations as depicted in early star charts, it’s hard to see how connecting the dots makes the stars take the forms the constellation’s name implies, but the images are still useful memory joggers. Modern science, though, gives us even more reason to remember these two stars, or rather the faint companion stars that orbit them. These are designated Procyon B and Sirius B and they defy our ability to even imagine because there’s just nothing in our down-to-earth experiences that compare with these tiny stars.  One of these “pups”  – the one belong to Procyon – is impossible to see with a backyard telescope and the other an extreme challenge.  The reason is they are quite dim and being very close to the bright stars, get lost in the glare. But the mystery of these two fainter stars is that they are both white, indicating they are among the hottest of stars. So how could something be that hot, that close to us, and yet so dim? And the answer is more mind-boggling than the question – they are both white dwarfs, and white dwarfs are a class of stars far denser than anything we encounter on Earth. Now I always find talk of the density of stars counter-intuitive because it gets drilled into our heads that stars are gas and the gas we encounter in our daily lives is anything but dense!  In fact, it’s quite – well – gaseous!  To appreciate this, let’s take a close look at our own Sun.

The Sun is a ball of gas which reaches densities that near the center are sixteen times that of lead!  That alone should stretch your mind. But now imagine the white dwarf. The stuff that makes up a white dwarf is about one million times denser than the stuff in the Sun. Jim Kaler writes that if you had a billiard ball made up of the stuff of one of these white dwarfs it would weigh about 70 tons – roughly the weight of an M1 Abrams tank. (Think of what that would do to your pool table, not to mention your foot if it fell on it!)  We know this because we can calculate the mass of the stars by their orbit around their bigger, brighter companions. The result is, we end up with a mass roughly that of the Sun but a size roughly that of the Earth. You can fit one million Earths – and therefore one million white dwarfs – inside the Sun. (See why a white dwarf is one million times as dense as the Sun?) How do you take all that mass and squeeze it down to such a small size? The physics of how that’s done goes way beyond me, but if you want to put a name to it, a white dwarf consists of “degenerate matter.” Unlike other stars, white dwarfs no longer burn with nuclear fires. In fact, they are no longer burning at all. They are the dying embers of stars – and in the case of the “pups,” the embers are being seen while still white hot. But they will eventually cool.  The name white dwarfs is given to this class of stars, but in truth not all white dwarfs are white – some can even be red. To make sense of this contradiction of terms, just think about an ordinary dying ember and how its color will change as it cools. So it is with these dying stars. Unable to generate any heat, what they radiate they lose. This is also the ultimate fate scientists expect for our Sun.  As it eventually exhausts its nuclear energy, it will turn into a bloated red giant like Betelgeuse in Orion.  Later still it will blow off its outer shell of gases, turning into a planetary nebula, such as the Ring Nebula (M57) in Lyra.  And at the core of that nebula will be the dying ember we know as a white dwarf. I’ve never seen the white dwarf that revolves around Sirius, but perhaps this season I will. Orbits are not circles, but ellipses. This means that sometimes there’s more distance between Sirius and its “pup” than at other times – and we happen to be in a period of several years when that distance will be growing, and so it will become easier to see the pup in a good, backyard telescope. (Sirius B completes an orbit around Sirius A in 50.2 years. Procyon B, while visible to professionals, is just simply too difficult a target for most backyard telescopes.) I also plan to take a close look at Adhara with a telescope, for it has a 7.5 magnitude companion just 7 arcseconds away. This should be a challenge – because of the difference in brightness of the two -  but not nearly the challenge that seeing the companion of Sirius. For those with binoculars and small telescopes, some of the most fascinating objects are in this general area of sky, near, or inside the Winter Hexagon, including the Pleiades, the great Orion Nebula, and the spectacular telescopic open clusters in Gemini and Auriga, M35, M36, M37, and M38. All that star light certainly can make for bright nights during the dark  of a northern winter.

Vital Stats for the Guidepost Stars

For Procyon:

• Brilliance: Magnitude 0.38, the 7th brightest star in our sky. Shines with the luminosity of about 7 Suns.
• Distance: 11.4 light years
• Spectral Type: F
• Position: 07h:39m:18s, +5°:13′:29″
• Procyon B is magnitude 10.7 and orbits Procyon in 40.8 years.  It can be as close as 9 AU to Procyon (1 AU is the distance between the Earth and Sun), or as far as  21 AU.

For Sirius:

• Brilliance: Magnitude -1.5,  the brightest star in our sky.  Shines with the luminosity of about 23 Suns.
• Distance: 8.6 light years
• Spectral Type: A
• Position: 06h:45m:09s, -16°:42′:58″
• Sirius B is magnitude 8.3 and orbits Sirius in 50.2 years. It can be as close as 8.1 AU to Sirius, or as far as 31.5 AU. (It will reach this greatest separation in 2019.)

For Adhara:

• Brilliance: Magnitude 1.5, it has a luminosity to the eye of 3500 times that of the Sun! (In other words, much brighter, really, than Procyon or Sirius.)
• Distance: 405 light years
• Spectral Type: B2
• Position: 06h:59m, -28°:59′:18″

Here’s an excerpt:

The concert hall at the Syndey Opera House holds 2,700 people. This blog was viewed about 31,000 times in 2011. If it were a concert at Sydney Opera House, it would take about 11 sold-out performances for that many people to see it.

Click here to see the complete report.

Really special astronomical events are rare – not only because they’re – well – rare, but because they are made rarer by having all the right conditions line up for your particular location, the final one being your personal schedule and, of course, the unpredictable weather.

In 2012, however, there will be at least two such events, both of which favor the US, though the first  ( the Quadrantids meteor shower) favors the East Coast a bit more than the West Coast (which is why I say it’s “our” turn since I live on the East Coast) – and the second, a transit of Venus in June, favors the West Coast a bit more than the East Coast.

Venus Transit  - See it in 2012, or wait for more than a century

In June, you say? Tell me about it later – say May.

And I will do so then in detail – but it’s not too early to mark your calendar now and thus keep it in your personal planning. So circle June 5, 2012. What is a transit of Venus? It’s a time when we can see Venus as a black dot cross the disc of the Sun – a time when Venus is actually between us and the Sun – and it happens rarely.  There have been just seven such transits since the invention of the telescope! And – of course – be careful! You will need special equipment to observe such a transit. Never look at the sun either with your naked eye or any  binocular or telescope unless it is one especially equipped just for looking at the Sun.  Such equipment isn’t expensive, though, and if you already have a telescope, would be a good investment to consider for this event and to regularly see  sunspots. I’m sure there will be several public observation points set up for those who don’t have such a telescope.

For me these are equally exciting events to witness, but the Venus transit carries the added bonus of happening in warm weather at a reasonable hour and has a whole bunch of science history associated with it – plus it isn’t going to happen again in our lifetime – unless in the coming years we find really wondrous ways to add to lifespan. Why historical?  Because scientists a couple hundred years ago lead dangerous and adventure-filled expeditions to observe a similar transit which was seen as a sort fo Rosetta Stone that would unlock all the important numbers of the solar system, giving us all planet distances and sizes.  At that time Kepler’s wonderful laws had given them the proportions of the Solar System – but they had no specific figures to plug in and no obvious way to measure any key one, such as the distance from the Earth to the Sun.  No way except this wonderful idea of observing a transit of Venus from two widely separated places on Earth – creating a baseline for a huge triangle –  and then using relatively simple math to derive the right numbers.

In Westport I will have only a couple hours to watch a portion of the transit before the sun sets, but that’s enough if the weather is clear. Here’s a simulation created using Starry Nights Pro software, of what I expect to see. It takes about a minute. Watch the top of the Sun for the entry of the dot that represents Venus.

Ok – enough – the date to reserve for Venus and the Sun is June 5. If you’re eager now for more details, go here.

Here come the Quadrantids – I mean right now!

As for the Quadrantids, I gave a head’s up on those last month because the date is right at the beginning of the year – the night of January 3-4 – which in this case really means the early morning of January 4.  Yes, I know for most locations it’s really cold at that time – this is mostly a northern hemisphere event – and morning isn’t everyone’s cup of tea – but as meteor showers go this can be really special.

The rarely seem Quandrantids (I’ve caught them once in over half a century and not at their best) are predicted to peak around 2-3 am EST on January 4.  (For the rest of the world that’s 7-8 hours Universal time January 4, 2012. Go here to convert Universal Time to your time.) 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 in Massachusetts 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. (Earlier when the moon is still up , it will be in the opposite corner of the sky to the shower’s radiant, so won’t offer much interference for those who would prefer to start around midnight.)

These links will take you to a couple of good examples of bright Quadrantids in previous years. This is a great individual meteor and ina serie sof images shows the trail it left.This leads to a nice series of photos of last year’s Quadrantids which peaked over Europe.

Where to look

So, if you love morning, if you love cold weather, and if you love gambling –  the Quadrantid meteor shower is for you!  Even if they don’t produce many, the ones that do show can be very bright so I wouldn’t discourage those in other parts of the Northern Hemisphere from looking – they’ll just see a lot fewer than those in a lucky location.

Quadrantid radiant point as it appears at 3 am January 4 from 42° N latitude. Click image for larger version. (Chart is screen shot from Starry Night Pro.)

What’s more, the Quadrantids are known for producing fireballs – the very brightest of meteors – ones that can even outshine Venus!

So how will you know a Quadrantid when you see it. After all, on any given night there can be several random meteors. The key is to note its direction. If you’re in North America, Quadrantids will generally come from the north northwest in the early evening, from north about the time of the shower’s peak, and from the north northeast later. As with so many good showers, the time to see the most Quadrantids will be in the early morning – essentially from about 1 am January 4, 2011, on.

This chart, taken from the American Meteor Society page here, is an excellent depiction of Quadrantids (the dark, straight lines) and for me drive homes the point that while the radiant is in the Northeast, the meteors can appear anywhere in the sky – afterall, that’s what the word “radiant” sure implies.

Click image for larger version. (From the American Meteor Society website.)

Here’s good advice from the American Meteor Society on this year’s Quandrantids:

Maximum rates for this shower are difficult to predict. Most observers across North America can expect to see a maximum of 40 Quadrantids per hour on the morning of January 4^th. If you are lucky it could be several times higher.

A good observing strategy for observers in North America would be to begin observations near midnight. This will allow eastern observers to catch the maximum should it arrive a bit early. Pacific observers may want to start around 2300 (11pm) on the 3^rd. While rates would most likely be low for western observers, any Quadrantid activity would be in the form of earth-grazing meteors, which are long-lasting and produce long trails as they graze the upper atmosphere. Face anywhere in the north to east quadrant, with your field of view half way up in the sky. This will keep the moon at your back. Quadrantid meteors will shoot upward from the northeastern horizon until it [the radiant] gains sufficient height when it can produce meteor shooting in all directions.

Observers located in the northern hemisphere other than North American can expect to see approximately 25 Quadrantids per hour between moon set and dawn. Due to the high northern declination (celestial latitude) of the Quadrantid radiant, observers in the southern hemisphere will see very few Quadrantids. As seen from the southern hemisphere the Quadrantid radiant lies low in the north, if it clears the horizon at all before dawn.

Its name is Latin for is mural quadrant and refers to an instrument that was very important to astronomy before the time of telescopes. Check out this description.

And then there’s Jupiter, Mars, Saturn – and of course, Venus!

We’ve a wonderful planet show going on this month with the actors changing  positions on the celestial stage, but Jupiter still dominant with Venus on the rise and Mars and Saturn beginning to arrive early enough to catch the night owls and give us early morning-types a real treat.

Jupiter is still high in the south and in evening twilight will rival Venus in brightness. Well, not really, but it will appear that way because Venus, beaming in the western sky, will occupy a section of sky with a much brighter background.  Venus is actually about magnitude -4 and Jupiter  magnitude -2.6. Venus will get higher in the western sky each night – Jupiter will move slowly towards it.

Mars  and Saturn are still mainly morning objects, but that is changing rapidly. Mars comes up in the evening in January – but isn’t well placed for observing until later. As the Earth overtakes Mars in its orbit the two draw closer which for the naked eye observer means Mars gets a lot brighter (doubles in the course of the month) and for the telescope observer its disc gets significantly larger making it easier to detect some features.

Saturn rises close to midnight, but doesn’t become well placed for observing until the early morning. It still makes a spectacular naked eye sight, however, looking like a natural companion to the bright guidepost star, Spica.  In fact, when I first saw this pair a few weeks ago  my initial reaction was “what the heck are the Gemni twins , Castor and Pollux, doing low in the southeast!?” But while the brightness and spacing reminded me of Castor and Pollux, I knew it was the wrong section of sky and I also could see that one – Saturn – gave off a yellowish hue while Spica is the bluest of blues.

Finding Saturn and Spica is easy – you follow the arc of the Big Dipper’s handle and that will lead you first to another bright star, Arcturus and then t0 Saturn and Spica. Observing Saturn with a telescope is now a real treat because the rings are tipped to give us an excellent view of them – something that hasn’t been the case for the past few years.

Looking behind the scenes – what the actors are really doing

Watching the planet show is like watching a play where the real action is hidden from us and what we see gives us an impression of bright stars which wander – “planet” means “wanderer” – among the “fixed” and generally dimmer stars. But lets lift up the curtain and go back stage.

The following series of images – click on each to get a much larger version – focuses on the motions of Venus between now and the June 5th transit of the Sun.  The larger image shows the western sky about 30 minutes after sunset at the start of each month. It is a screen shot from SkySafari Pro software. I have added to it a screen shot that uses the online Orrery found here to show the actual position of the inner planets as seen from a vantage point above the Sun. I love this sort of thing. It’s simply cool to stand outside, see a planet, and really be able to visualize where you are and where it is. Afterall, astronomy is largely a game of such mental gymnastics and understanding these things makes your observing experience more meaningful.

So if you study the changing Orrery view you can see how the motions of the planet all relate to what we actually see in the sky.  Draw an imaginary line from the Earth through the Sun and that line marks the difference between evening and morning. From our vantage point on earth as we rotate and approach a view of the Sun each morning we see the planets that are in our morning sky – and once we pass the Sun  - as night falls – what we see is in our evening sky. That’s why I marked an “evening” and “morning” side for each Orrery view.

With that in mind, here are the images leading up to the Venus transit for the first of each month, starting with January 1, 2012. (Be sure to click on each image for the larger version.)

Looking west,  half an hour after Sunset, January 1, 2012

Looking west, half an hour after Sunset, January 1, 2012 Click image for larger version. Prepared from SkySafari Pro screen shot.

Looking west,  half an hour after Sunset, February 1, 2012

Looking west, half an hour after Sunset, February 1, 2012 Click image for larger version. Prepared from SkySafari Pro screen shot.

Looking west,  half an hour after Sunset, March 1, 2012

Looking west, half an hour after Sunset, March 1, 2012 Click image for larger version. Prepared from SkySafari Pro screen shot.

Looking west,  half an hour after Sunset, April 1, 2012

Looking west, half an hour after Sunset, April 1, 2012 Click image for larger version. Prepared from SkySafari Pro screen shot.

Looking west,  half an hour after Sunset, May 1, 2012

Looking west, half an hour after Sunset, May 1, 2012 Click image for larger version. Prepared from SkySafari Pro screen shot.

Looking west,  at Sunset, June 1, 2012

Looking west, at Sunset, June 1, 2012 Click image for larger version. Prepared from SkySafari Pro screen shot.

Here’s the chart for the eastern sky one hour after sunset for mid-northern latitudes. Remember, going out about 45 minutes after sunset and looking east, you’ll see only the brightest stars as they come out. This makes it easier to identify and learn our guidepost stars. Our guidepost asterisms may not be as readily seen until a little later as the sky gets darker and more of the fainter stars come out.

Click here to download a black-on-white (printer-friendly) version of this chart.

The January eastern sky – what to remember

• Castor – A trio of twins
• Pollux – The bigger, brighter twin
• Orion – A man for all to see
• Betelgeuse – a giant among giants
• Rigel – Blue and brilliant

 Castor – A trio of twins

When you see Castor, think “twins” – a trio of twins. Well, in a sense there are really four pairs!

But the fourth pair is just mythological – Castor is one of the “heavenly twins” of the constellation Gemini – the other twin being Pollux. This is nothing but a fanciful relationship, though, based on how the stars appear to us – and appeared to ancient cultures as well. But there is more, much more, to Castor. And, it’s what we don’t see that makes this bright star so fascinating. And seeing withy our mind’s eye – your knowledge of what you are seeing – always enhances your experience under the night sky.

So were you to look at Castor in a backyard telescope, you would see it has a twin – another bright star that appears quite close –  the two are known simply as Castor A and B. These two are related, orbiting one another about every 400 years. But there’s more. Each of these two are twins! However, you can’t see this in a telescope because in both cases the pairs of stars are extremely close to one another, orbiting one another in periods of less than 10 days. And as noted, each pair orbits the other pair in about 400 years. But there’s more.

Returning to that backyard telescope you may notice a third star, Castor C, quite a distance from the first two and significantly dimmer. This star is also part of the Castor family and it too has a twin that also is so close we can’t detect it without special instruments. In fact, Castor C consists of the closest pair of all, orbiting one another in less than a day! This pair, in turn, orbits the other four stars in the system once every 10,000 years or so.

So when you look at Castor, remember that in classic mythology it has a twin, Pollux – and remember that what looks to you like a single bright star is really the combined light from six stars, all held together in one of the most complex star systems we know. (I wrote much more about the Castor system on the double-star blog. That post includes a scale model that puts Castor and company into perspective with the Earth and Sun. You’ll find it here. )

Vital stats (for just the brightest star in the Castor system):

• Brilliance: Magnitude 1.58, the 23rd brightest star in our sky and the brightest second magnitude star. Absolute magnitude is 0.9. (Yes, we call a star “second magnitude” if it’s magnitude is between 1.5 and 2.5 – so you can see castor just slips into this category.)
• Distance: 50 light years (not among the 200 nearest stars)
• Spectral Type: A
• Position: 07h:34m:36s, +31°:53′:18″
• Compared to the Sun: Castor radiates 14 times as much energy as our Sun.

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Getting to know Pollux – the bigger, brighter twin

How Bayer saw the Gemini Twins in his 1603 atlas. (Image courtesy of Linda Hall library of Science, Engineering and Technology.)

Pollux should feel a little cheated because it’s the brightest star in the constellation of Gemini and usually the brightest star was given the designation “alpha”  by the early chart maker, Bayer. Not Pollux. It is designated “Beta Geminorum” and follows its slightly dimmer twin brother around the sky. But Pollux has its own way of standing out: It has a slight edge in brilliance in our sky; it is a tad closer to us; and it is an orange giant. What’s more, in 2008 it was confirmed to have a planet orbiting it.

As an orange giant, it has moved off the “main sequence,” and instead of fusing hydrogen into helium, as our Sun does, it is fusing helium into carbon and oxygen. It will eventually blow off a lot of its substance becoming a planetary nebula. It is currently about eight times the diameter of our Sun – that’s huge, but nowhere near as large as our next star, Betelgeuse. The planet circling Pollux is also large – “Jupiter class” – and was first detected in 1993, but not confirmed until 2008.

Vital stats:

• Brilliance: Magnitude 1.14, the 17th brightest star in our sky. Absolute magnitude is 0.7 .
• Distance: 34 light years (not among the 200 nearest stars)
• Spectral Type: K
• Position: 07h:45m:19s, +28°:01′:35″

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 Orion – A man for all to see

If you’re in the same general latitude as I am in Westport, MA, then you see Orion like this as it rises in the east on a January evening.

What always sticks with me about Orion is how Robert Frost described him in his wonderful poem, “The Star Splitter.”

‘You know Orion always comes up sideways.

Throwing a leg up over our fence of mountains,

And rising on his hands, he looks in on me . . .

But if I lived in Sydney, Australia, I wouldn’t see it this way. What I would see is a man standing on his head!

The real point here is that these stars do look like a man, and they can be seen from deep into both the southern and northern hemispheres. What’s more, the three distinctive stars that form Orion’s belt also mark the approximate position of the celestial equator in your sky, a handy thing to know. Of course, if you’re in the southern hemisphere, the celestial equator appears to make an arc across your sky to your north. In the northern hemisphere it appears to make an east-west arc across the sky to the south.

But in either case the belt stars of Orion will rise just about due east and set due west. How high they get in your sky is calculated simply by subtracting your latitude from 90. That is, if your latitude is 42 degrees, as mine is, then Orion’s belt will be, at its highest, about 48 degrees above the horizon when it passes due south. From Sydney, Australia, the stars in the belt will cross about 56 degrees above the horizon as they pass due north. And yes, if you live on the equator these stars will cross directly over head. Anyway you look at it, Orion is a man for all latitudes – well, almost. At the north pole you would only see his top half, and at the south pole, only his feet! Return to Menu

Betelgeuse – giant among giants – and Rigel’s pretty large as well!

When you look at the eastern sky early on a January evening, get this picture in your head!

Yes, that’s rigel represented inthe illustration, not Betelgeuse. Classified as a red supergiant, Betelgeuse is one of the largest stars you can see – and certainly up there with the biggest of all stars – yet it doesn’t look any bigger in our sky than other stars because all stars, except the Sun, are so far away they appear only as a point source of light to our eyes. Last month we showed what Aldebaran would look like if it were in our sky and the same distance from us as the Sun, and this month we’ve added Rigel to the picture. But we can’t do a similar thing with Betelgeuse – it wouldn’t be in our sky – it’s so large we would be in it if it were located where our Sun is!

What’s more, it’s hard to put a number to the size of Betelgeuse, not because it can’t be measured, but because it’s hard to decide exactly what you want to measure when you’re dealing with a ball of gas – especially one like Betelgeuse. Our Sun is a little easier case. While it does not have a surface, it does appear to us to have an edge that’s fairly easy to define – it’s the place where its gases are dense enough to be opaque to our vision.

Exactly how we define the size of Betelgeuse is a bit more difficult. I rely on James B. Kaler as my stellar authority. I love his books, and in one, “The Hundred Greatest Stars,” he describes the size of Betelgeuse variably as:

• 650 times that of the Sun, or 2.8 AU (Astronomical Units – an Astronomical Unit is the distance between the Earth and the Sun – roughly 93 million miles)
• 800 times the diameter of the Sun, or about 4 AU
• 1600 times the Sun – about 8 AU when measured by modern observation in ultraviolet light

And on his Web site, after opting for a figure of around 8-9 AU, he writes:

However, the star is surrounded by a huge complex pattern of nested dust and gas shells, the result of aeons of mass loss, that extends nearly 20,000 AU away (Betelgeuse so far having lost over a solar mass). That, an extended atmosphere, and the pulsations make it difficult to locate an actual “surface” to tell just how large the star actually is. Moreover, because of changes in gaseous transparency, the “size” of the star depends on the color of observation.

Betelgeuse has other problems. The pulsations he refers to are a sort of puffing up that occurs from time to time and changes both size and brightness significantly. Betelgeuse is usually thought of as about magnitude 0.55, but it can be as bright as 0.3, or as dim as 1.1. All this huffing and puffing will soon lead to an explosion, and Kaler says it will then be as bright as a crescent moon! But don’t hold your breath. “Soon” in astronomical terms means sometime in the next million years or so! Its distance, too, is uncertain, but 500 light years is a good ballpark figure.

Let’s focus on that 8 AU size for a moment. When we build a scale model of our solar system and reduce the Sun to something about the size of a volleyball, the tiny speck of the Earth orbits at around 75 feet away. But at 8 AU Betelgeuse would be more like 600 feet in diameter. So pause for a moment as you look at Betelgeuse on a winter evening. Imagine yourself holding an 8-inch volleyball in one hand – our Sun – while you stand next to a red, raging, unstable monster ball that is 600 feet in diameter!

Vital stats:

• Brilliance: Magnitude 0.3 – 1.1, the 10th brightest star in our sky (sometimes). Shines with the luminosity of about 90,000 Suns.
• Distance: 570 light years
• Spectral Type: M
• Position: 05h:55m:10s, +7°:24′:25″

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Rigel – Blue and brilliant

Here we go again! Like Pollux, it looks like Rigel was short-changed having been designated the “Beta” star of the constellation Orion while dimmer Betelgeuse is the Alpha. Of course, Betelgeuse, being variable, may have been brighter when Johann Bayer made his designations in 1603. Bayer’s “system” is inconsistent, however, to say the least, so there’s no sense getting too worried about this.

Like Betelgeuse, Rigel is a supergiant. It’s huge and it’s brilliant too – and since it is more distant (860 light years), it is intrinsically more brilliant than Betelgeuse. Jim Kaler writes: “Only about 10 million years old, Rigel should eventually expand to become a red supergiant very much like Betelgeuse is today, by which time it will be fusing helium into carbon and beyond in preparation for its eventual explosion as a supernova.”

Rigel’s radius is 74 times that of the Sun, 0.34 Astronomical Units, nearly as big as the orbit of Mercury.

Rigel is a challenging double star for amateurs with moderate-sized telescopes.

Vital stats:

• Brilliance: Magnitude 0.12, the 7th brightest star in our sky. Shines with the luminosity of about 90,000 Suns.
• Distance: 860 light years
• Spectral Type: B
• Position: 05h:55m:10s, +7°:24′:25″

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Click here to download a black-on-white (printer-friendly) version of this chart.

Of course, Polaris – the “North Star” – is really not exactly north. It’s just a very good approximation of north. True north in the sky is the North Celestial Pole – a projection of the Earth’s north pole – and it would be too much to hope that a bright star would be parked on this exact spot. But if you have binoculars, point them at Polaris on a dark, clear night – one where there’s no interference from the Moon – and you should be able to see a neat little asterism called the “Engagement Ring,” a crude ring of 7th and 8th magnitude stars with Polaris forming the diamond. Look carefully and you’ll see this ring tells you the direction and distance to the true north celestial pole.

Of course, Polaris, as with the other stars, travels in a great circle around the pole. But, the relationship between the Engagement Ring, Polaris, and the true North Celestial Pole, remains the same, and south is defined as the direction away from the pole, north the direction towards the pole, and west is the direction the stars appear to rotate. For more on finding directions in the night sky, see this post. See the movie below, made with Starry Nights Pro software, to see how Polaris and the Engagement Ring rotate around the celestial north pole in the course of 24 hours.

High above Polaris the familiar “W” of Cassiopeia has completed its transition to an “M” as its stars roll around the pole. Off to the northwest near the horizon we see two bright guidepost stars, Vega and Deneb. To the northeast we have brilliant Capella.

The Big Dipper is easy to spot because it’s stars are bright. But folks frequently have trouble with the Little Dipper  and that’s no surprise because many of its stars are faint.  So don’t be alarmed if you can’t pick out most of the Little Dipper stars – four of them are fourth magnitude or fainter and besides, they are below Polaris this month, making them even more difficult to see since you are looking through more atmosphere when stars are low. I see them only when it has become fully dark – about 90 minutes after sunset – and when my eyes have had 10-20 minutes to dark adapt.

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.

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.

Click for larger image - Stellarium screen shot.

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.

"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 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.

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

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.

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.

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.

With the naked eye the planets look like stars and we can follow the path of the five brightest in our skies this month. With binoculars we can add Uranus and Neptune to our list and even see the four brightest moons of Jupiter. (NASA composite image. Click for larger version.)

It’s a feast in the east for November 2011 with Jupiter dominating that section of sky in the evening and Mars and Saturn taking over in the morning. Meanwhile, over in the west we have the Venus/Mercury show developing in the second week of the month.  And how about the middle of the sky? Well, there we have the always challenging-to-find planets, Uranus and Neptune.  Binoculars are a must to sight them. And if you’ve been counting, you know that’s all the planets! (Pluto – well, it’s a “dwarf planet” and it’s heading behind the Sun this month, and even if it were well placed it would be out of reach of the naked eye, binoculars, and even small telescopes.) Add to this a comet and the special fun the moons of Jupiter offer, and it really should be a very good month.

An appetizer: take a 2.5 million year star trek to the Great Andromeda Galaxy

But wait! That stuff is all in our back yard – we can get to any of those planets in a matter of minutes – light minutes, that is! (Light travels around the earth seven and a half times in a second , yet it takes it about 30 minutes to reach Jupiter!)  But early evenings in November – especially when there’s no moon to compete as will be the case in the last half of this November (2011) – offers another special treat for binocular users – the Great Andromeda Galaxy.

The Great Andromeda Galaxy as seen by the Hubble Space Telescope. It won't look quite like this, but you too can see it with binoculars.

This is our neighbor in space –a galaxy much like our own Milky Way. And with dark skies free of the worst of light pollution you can actually glimpse it with your naked eye if you know just where to look. And it really is a glorious sight in even ordinary binoculars, especially when you understand that the small cloud you see is really 300 billion suns and their light is reaching you after journeying for two and a half million years! I don’t mean to detract from the planetary show, but if you have binoculars and clear skies, you really should take this “trek.” It will be especially good during the last two weeks of the month when the Moon doesn’t wash it out.

Review the eastern sky chart in our “Look East” post for this month, then use the chart and instructions below to zoom in on this galaxy – and when you do, give yourself a pat on the back as a genuine star trekker.

To find the Andromeda Galaxy use half of the "W" of Cassiopeia as a pointer. Or take a star hop down Andromeda's Couch, then up a couple of hops as shown. You should be able to fit stars 3 and 4 in the same binocular field of view, then stars four and the galaxy in the same field. Click for a larger version. (Created from Stellarium screen shot.)

(Here’s a printer-friendly, black and white version of the chart above.)

Back to the planets – they  line up like this

• Jupiter can’t be missed. It’s the brightest “star” low in the east right after sunset.
• Venus gets started on one of its spectacular appearances during which it will dominate the western evening sky for months.
• Mercury plays coy and hard to catch, but Venus gives it away as it peeks above the western horizon right after sunset.
• Mars is getting higher and higher in the morning sky and actually rises before midnight for part of the month. It continues to scoot right along, this month playing tag with the bright, guidepost star, Regulus.
• Saturn is a morning sky object that will excite telescope users because its rings are at last returning to a favorable tilt from our perspective.
• Uranus and Neptune are the difficult ones. They are both reachable with binoculars and in prime time, but they are challenging to find.

So that’s the line-up – read on for details. Or jump ahead to what interests you by clicking on one of the links above.

The Feast in the East 1 – Jupiter and the Algol bonus

Jupiter is in its prime – and dominating our prime-time observing - nice and high, nice and big, and with dancing moons that you can even see in binoculars if you can only find a way to hold them steady enough. Fortunately, there are several neat techniques pictured here that you could use to hold any binocular steadier. I used the “rifle sling” technique pictured on that site with my 15X70s and it helped significantly. But no matter what the size of your binoculars, you increase your chances of seeing Jupiter’s moons if you can get them rock steady.

Most binoculars have a threaded center post that allows you to use an inexpensive adapter to mount them on a typical camera tripod. This is good as long as the object you are looking at is not too high in the sky. Once it gets above 45 degrees it’s very difficult to position yourself behind binoculars that are on an ordinary tripod. (Go here to see one example of tripod adapters for binoculars.) So this is a good approach this month up until about three hours after sunset as Jupiter climbs higher each hour.

When you are looking at Jupiter’s moons, it’s fun simply because they are constantly changing position from night to night – even from hour to hour. It’s also fun because they are surprisingly diverse worlds. In fact, the exploration of large moons throughout the solar system has been a constant source of surprise. So I suggest two things.

First, learn more about Jupiter’s moons by going here. (Pay special attention to the four “Galilean Moons” – those are the ones you see.)

Second, use this Javascript utility at Sky and Telescope to figure out which moon is which when you actually observe them..

And while we’re on the subject of handy tools at Sky and Telescope, also use their utility to figure out when it would be a good time to catch the surprisingly elusive Demon Star – aka Algol - when at its minimum. This is something you don’t need binoculars to see – it’s best done with the naked eye. I explained it in more detail last month.

Feast in the West – Venus and Mercury

Venus and Mercury line up almost due southwest with the sun setting halfway between southwest and west. BE SUPER CAUTIOUS! To see these you will need binoculars, but looking at the Sun with binoculars will cause immediate damage to your eyes. So wait 10-15 minutes after sunset, then start your search. Venus should be bright enough even in twilight to see with the naked eye once you know where to look, so it helps to find it first with binoculars. (Prepared form Starry Nights Pro screen shot.)

From roughly the 9th to 22nd of November 2011 Venus and Mercury will appear  in the same binocular field of view about 15 minutes after sunset. They are attractively aligned in an arc or line for just a few days starting on the 9th.  I’ve included Antares because it makes such a nice picture, but it’s more than a magnitude fainter than Mercury and much, much fainter than Venus (magnitude -3.8) and closer to the horizon, so I think it will be a difficult target. You need, of course, an unobstructed western horizon and very clear skies. Fifteen minutes after sunset Venus is less than a fist above the horizon. Half an hour after sunset it’s just half a fist high, and if you haven’t spotted it by then, you probably won’t as it will get lower fast and the closer to the horizon, the more difficult to see.

Please be careful and don’t begin your search with binoculars until 10 minutes after sunset so there’s no danger of catching the Sun in the binoculars and damaging your eyes. As the days go by Mercury stays about where you see it and Venus pulls away to the south, getting higher as Mercury begins to sink.

The Feast in the East 2 – Mars, Saturn, the Moon and stars

Now this is cool!  On November 22, 2011, you won’t have any trouble locating Saturn because it will be within a fist of the crescent Moon with Spica, about one magnitude brighter than Saturn, between it and the Moon. High above them,  Mars has passed Regulus, and is just about the same brightness as Saturn.  But you can find these planets just about any morning of the month, using the bright guidepost stars as your guide. Follow the arc of the Big Dipper’s handle and it takes you to Arcturus. Keep following this general curve and you get to Spica – passing through Saturn on the way.  Both Spica and Arcturus are  bright guidepost stars, as is Regulus. Mars will be within one fist (10 degrees) of Regulus all month. Mars starts out west (above) it on the first of the month, passes closest to it on the morning of November 11, and will be about one fist east (below) it by the end of the month.  Saturn will stay roughly half a fist (5 degrees) from Spica all month, changing position much more slowly than Mars since it is much farther away from us.

Click on image for a larger version. Prepared from Starry Nights Pro screen shot.

Challenge in the Middle – Uranus and Neptune

The early evening of the last half of the month is a good time to look for these planets since the Moon will not offer interference then – but you need to wait until about 90 minutes after sunset so it is completely dark.

This is where knowledge of the sky certainly helps – with a little knowledge it’s as easy as one, two – to find Uranus; and one, two, three to find Neptune. Here are the steps

One – Get your bearings.

Know the sky in the vicinity of these two planets. In particular you want to locate a relatively dim asterism known as the “Circlet” to guide you to Uranus, and two others, the “Water Jar” and “Arrowhead” to find Neptune. The starting point, however, is an asterism that should be familiar to you – the Great Square – and if it isn’t, please go to the “Look East” post for this month and locate it.  Then study the following chart – click on it to see the larger version.

Step one - get familiar with the big picture. The red circle between Uranus and Neptune is the field of view of typical, low-powered, binoculars - good tools for finding these objects. The Great Square and Jupiter should be easy to find because they're both bright. The "Circlet" is fourth and fifth magnitude stars that you need to be away from light pollution to find, but even in light pollution you can spot them with binoculars. However, the whole Circlet will probably not fit in your field of view. The Water Jar will fit in the typical binocular field and so may be an easier target. What I call the "Arrowhead" is the constellation Capricorn. The star at its northeastern corner is bright enough to see even in light-polluted skies and so is a good starting point for finding Neptune. Click image for larger version. Prepared from Starry Nights Pro screen shot.

Step 2 – Zoom in on Uranus . . .

Assuming you have located the Circlet, now turn to this chart. The brightness of the planet in comparison to nearby stars is a good guide and will give you some idea of what to look for and whether or not it’s visible in your skies. The numbers on the chart refer to the magnitude of a star or planet. They are given without a decimal point so as not to confuse the chart with dots that aren’t stars. Thus the number “51″ means a magnitude of 5.1 – and remember, the lower the number, the brighter the star!

Scan below the Circlet with your binoculars. The little rectangle of fourth and fifth magnitude stars should be easy to pick up and will help you find Uranus. Note that Uranus at magnitude 5.8 is half a magnitude or so dimmer than the stars in the rectangle, but a bit brighter than the 6.3 star next to it. The position of Uranus will change very little during the month. Click on image for larger version.

  . . . or alternative Step 2, zoom in on  Neptune

Neptune is more challenging, but if you can locate the third magnitude star Deneb Algiedi in the northeastern corner of the Arrowhead asterism, you will be well on your way. (It’s on the bright side of third magnitude, so should be fairly easy to find.)

Once again, the numbers next to stars are their magnitudes with the decimal point left out. So Neptune is magnitude 7.9, for example. It will be right near the edge of visibility in low power binoculars and you'll need the next chart to pick it out from the background stars. Click image for larger version. Prepared from Starry Nights Pro screen shot.

And now Neptune Step 3 – up close and personal

The bigger – and steadier – your binoculars, the easier it will be to see Neptune. It’s also important that your eyes be dark adapted. You’ll be looking for a faint “star” among several. Here’s a close-up chart.

Click image for larger version. Prepared from Starry Nights Pro Screen shot.

Did I mention the comet?

The comet is one that requires binoculars, but it’s still fun and is unusual in that it will be with us right up to the spring. I’m talking about Comet Garradd which we met at the end of August and start of September when it was hanging around with my favorite binocular asterism, the Coathanger.  Here’s a chart for its path in the last half of November.

At 6th magnitude Comet Garradd is just below naked eye visibility for most of us, but you should be able to pick it up in binoculars as a faint, fuzzy star. I doubt very much that you'll see a tail, but if you do it should point the direction shown in the chart. The chart is for 90 minutes after sunset - look west and find the Keystone of Hercules as a starting point. The second and third magnitude stars - Rasalhague and Rasalgethc, should also be a big help in getting you in the right general area. Arrow shows movement of comet from November 15 to November 30 - a period when the Moon should not interfere with your search. On the 15th Comet Garradd will be about three fists above the horizon 90 minutes after sunset - by the end of the month it will be about two fists. Click image for larger version. Prepared from Starry Nights Pro screen shot.

And if you’re wondering where the November meteors went, the Moon ate them!

Yes, last year at this time we were talking about three minor – but interesting – meteor showers. They were the South and North Taurids and the Leonids.  They’ll still be around this year, but they are weak shares at best, and this year will be especially challenged by the Moon. But for the record, the South Taurids peak November 5/6 late night until dawn; the North Taurids November 11/12th; and the Leonids November 17/18.