Look Southeast in July 2014 – Colorful Stars and Planets, Great Asterisms – even a Great Constellation!

We’re going to cheat a little this month and look quite a bit south of east, rather than due east. The reason is we have some wonderful stars getting as high as they get if we look that way – AND we have two bright planet and colorful planets, Saturn and Mars which make for some interesting comparisons with nearby stars. We also have a couple of really cool asterisms and even a great constellation.

I’m not a big fan of constellations. Most don’t look anything like their names imply; some are quite obscure; and many simply can’t be seen in typical suburban skies these evening because of light pollution. Scorpius is an exception. It looks like the Scorpion of its name – a truly beautiful constellation with its graceful, curving tail. What’s more, many of its brighter stars actually do hang out together – they are not just an accident of our line of sight.

The Scorpion as Bayer saw him in his 1603 illustrated star atlas, Uranometria. Click for a much larger image. (Used by permission from the Linda Hall Library of Science, Engineering & Technology.)

It dominates our southeastern sky in July, just as the Summer Triangle – a terrific asterism, dominates our eastern sky this month. And we have two fascinating new “guide” stars – the intriguingly close and rapidly spinning Altair – and the incredibly huge and red Antares that is right at the heart of the Scorpion!

Antares begs comparison with Mars – both being red. But Mars is also very, very close to a bright blue star, Spica. Mars will be just a bit brighter than either of these comparison stars. Saturn –  between Mars and Antares and also very bright, has a yellowish hue.

But the real treat at this time of year remain these southern stars. They never get real high and from mid-nothern latitudes we only get a couple hours on a summer night when they are really well in view above the southern horizon. To top it all off the Milky Way runs from Deneb in the  Summer Triangle to the tail of Scorpius,but you have to wait a couple hours after sunset before this comes out.

Let’s take a look at the chart, then examine Scorpius along with its quaint little companion, a very real looking teapot complete with “steam” coming out of its spout! Wow! Summer nights may be short, but they sure offer some nice visual treats!

Oh - about that "teapot." We won't discuss it, but you can clearly see it tagging behind the scorpion. If you have real clear skies, the Milky Way is beautiful in this area and looks like steam rising from the teapot. More on this next month. Meanwhile, click image for a larger version. (Developed from a Starry Nights Pro screen shot. )

Click to enlarge! This chart covers a bigger section of sky then we usually show. Vega, for example,  will be six fists up. Oh – about that “teapot.” We won’t discuss it, but you can clearly see it tagging behind the scorpion. If you have real clear skies, the Milky Way is beautiful in this area and looks like steam rising from the teapot. More on this next month.  (Developed from a Starry Nights Pro screen shot. )

First up is the Summer Triangle – it’s an asterism that you can’t miss, and it will grace our evening skies right up into early winter. If you’ve been following for a few months, you’ve already met its lead star, brilliant Vega. And last month we were introduced to Deneb on the other corner. In fact, we saw that we could make a quite impressive Northern Triangle out of Deneb, Vega, and Polaris. But far better known than that asterism is the Summer Triangle shown above of Vega, Deneb, and Altair.

Altair is hard to miss. It is the brightest star low in the east early on a July evening, but it is also distinctive because it has two reasonably bright companions, close on either side, that form a straight line with it. This is appropriate because it’s not hard to see Altair and those two companions as representing an eagle in flight, and that’s good because they are the major stars in a constellation known as Aquilla, the Eagle.

Altair is white, much like Deneb and Vega, and is even closer to us than Vega. Vega is 25 light years away, Altair just 16. That’s in contrast to Deneb, which you may recall is an astounding 1,425 light years (at least)  from us – astounding because even at that distance it is almost as bright as its much closer companions and some experts believe it is much more distant.

Altair also distinguishes itself by spinning incredibly fast. It takes our Sun almost a month to complete a rotation on its axis. Altair, almost twice as large as our Sun, spins once on its axis in just 10 hours. Why, I don’t know, but it’s one more reminder of how these stars, which all look pretty much the same to us because they’re so far away, all have their special traits that distinguish them as individuals.

The most obvious special trait for Antares, our other new guide star this month, is its redness – and it’s one of only four guide stars that is quite close to the ecliptic – the path of the planets. That means that reddish Mars comes close, sometimes, to reddish Antares, and that’s appropriate because the name “Antares” actually means “like Mars.” However, science tells us something else about Antares. It is huge. I mean BIG.

Get out your calculator and do a little simple math. (OK, I’ll do the math, but really – this is simple, and I think you would appreciate the numbers much more if you did the calculations yourself.) One possible source of confusion:  To visualize a sphere I use its diameter. To actually calculate things I need the radius – since a radius is half of a diameter  you’ll find me jumping back and forth between these two terms – don’t let it confuse you.)

So try this. Start with something manageable, like the Earth. It’s about 8,000 miles in diameter and that’s a number that’s fairly easy to imagine. Let’s reduce Earth to a ball 2 inches in diameter. It would have a radius, then, of one inch.

Now let’s make a scale model Sun to go with our Earth. That’s easy. The radius of the Sun is 109 times the radius of the Earth. That means the Sun will have a radius of 109 inches – roughly 9 feet. So now we have a one-inch Earth and a 9-foot Sun. So our scale model has two balls – one two inches in diameter to represent the Earth and one 18 feet in diameter to represent the Sun.

That certainly should tell you that the Sun is a lot bigger than Earth, but my problem is, these linear measures don’t give us a really good sense of the size difference. We need to visualize spheres in terms of volume. We can get a rough approximation of the  volume  of a sphere by simply cubing the radius and multiplying it by 4. If we do this for our scale model Earth we have (1 x 1 x 1) x 4 – or four cubic inches. Now to calculate the volume of our scale model Sun – in cubic inches – we multiply 109 x 109 x 109, then multiply that by 4. Wow! Well, if you tried it on your calculator I hope you said “Wow!” You should get 5,180,116. That means you can fit well over one million Earths in our Sun! That to me is a lot more impressive than the linear measure where we find the diameter of the Sun is about 109 times the diameter of Earth.

Now let’s do a similar exercise with Antares. Antares has a radius more than 800 times the Sun. Do the math. Our scale model Sun has a radius of  9 feet – our scale model Antares will have a radius in feet of 9 x 800. Man, that’s big. About 7,200 feet!  (Just remind yourself that a mile is 5,280-feet.)  So now we have three models – a 2-inch diameter Earth, an 18-foot diameter Sun, and a 14,400-foot diameter Antares – that last is approaching three miles!

Don’t bother to calculate the volume. Unless you use scientific notation, your calculator probably won’t handle it. But you get the idea. That little dot of red light we call Antares is B-I-G. And don’t forget – on this same scale the huge planet you are standing on is just 2-inches in diameter.

Here’s a graphic representation courtesy of Sakurambo:

Notice the artist didn’t even attempt to represent the Earth on this scale!

Think of it this way. If Antares were our star, both the Earth and Mars would be orbiting inside it!

That’s huge – even bigger than Deneb – which we noted last month was a “supergiant” – the same class that Antares belongs in. But Deneb would only reach about halfway to Earth – Antares would go past both Earth and Mars. Deneb, however, is a very young, very bright, very hot star, which is why it shines so brightly from such a great distance. Antares is much closer – about 600 light years vs at least 1,425 for Deneb. But Antares is old – a star in its dying stages, and is large and bright because it is so bloated. It really is quite cool as stars go – that’s why it appears red to us. But it has such a huge surface area that even from a distance of 600 light years it appears bright to us – a bit brighter in our sky than Deneb, actually.

So let’s briefly consider these four guide stars together – Vega is our “standard” star – white, about the size of the Sun, and quite close at 25 light years. Altair has some unusual features, but is still rather normal as stars go. Deneb is distinguished by being large and hot; Antares by being even larger, but relatively cool.

Vital stats for Altair (AL-tair), also known as Alpha Aquilae:

• Brilliance: Magnitude .77; its luminosity is the equal of 11 Suns.
• Distance:16.8 light years
• Spectral Types: A, main sequence
• Position: 19h:50m:47s, +08°:52′:06″

Vital stats for Antares (an-TAIR-ease), also known as Alpha Scorpii:

• Brilliance: Magnitude 1.09; its luminosity is the equal of 65,000 Suns.
• Distance: 600 light years
• Spectral Types: M, supergiant
• Position: 16h:29m:24s, -26°:25′:55″

Look north in July 2014 and take the measure of your skies and eyes!

Light pollution is a big issue these days. How does it impact you? Summer is a good time to check by looking north about two hours after sunset and seeing what stars you can see in and near the Little Dipper. Why summer? Because this is when the Little Dipper should be highest in your sky – standing upwards from Polaris, the North Star. Here’s what you should see on a typical July evening when you look north from mid-northern latitudes.

In summer the faint stars of the Little Dipper are high above the North Star. Click image for larger view. (Developed from Starry Nights Pro screen shot.)

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

The Big Dipper is diving downward in the northwest but is still very high, and its handy “pointers” should get you quickly to the North Star, Polaris. Roughly opposite the Big Dipper you should see the “W” of Cassiopeia starting to make its way upward in the northeast. And unless you suffer from really terrible light pollution, you should see the two “Guardians of the Pole” – the second and third magnitude stars that mark the end of the Little Dipper. The brighter of these two is just a tad dimmer than Polaris, but since it’s higher in the sky right now and thus shining through less air to get to you, it will probably look just the same as the North Star in brightness.

To do this test you first have to wait until it is genuinely dark, and in summer that’s a bit longer than in winter. Twilight actually is divided into three steps. We have civil twilight which goes from sunset until when the Sun is six degrees below the horizon. Nautical twilight is the next period, which continues until the Sun is 12 degrees below the horizon. Then you have Astronomical Twilight until the Sun is 18 degrees below the horizon. At that point it is as dark as it will get and will remain that dark until we run the sequence in reverse as the eastern horizon nears the Sun. As a rough rule of thumb, you can consider each twilight period to last half an hour – but the exact length depends on where you are on Earth and the time of year. If you want to get precise, go to the U.S. Naval Observatory site, fill in the form you’ll find there, and you can get a table that will give you the start and end of these twilight times – or for that matter when the Moon rises, or the Sun sets. It’s very handy. (Note: the preceding link takes you to a page for US cities and towns – but there’s a second page here where you can put in the latitude and longitude for any location in the world, including in the US. )

The second thing you need to do is make sure your eyes are dark adapted. They are casually reasonably well dark adapted after you have been out for 15 minutes and have not looked at any white lights. But it can take from half an hour to an hour of protecting your eyes from any white light for them to become fully dark adapted. That doesn’t mean you have to sit around in the dark doing nothing waiting for this to happen. In the last hour or so before full darkness there are plenty of things to see – just avoid bright lights. That also means moonlight. You’re going to want to do this when the Moon is not in the sky, for it will make it difficult to see faint objects anywhere near it. In July of 2014 the last two weeks should work pretty well for the evening hours – as will the first day or two of the month.  Other evenings, the Moon will dominate the early evening sky.   (A good Moon-phase calendar can be found here, though for this purpose I find the table from the Naval Observatory for local Moon rise is also handy!)

So here’s the test:

How many stars can you see in the Little Dipper?

Remember that in the magnitude system the higher the number, the fainter the star.

The Little Dipper consists of seven stars. Three are easy – Polaris and the two “Guardians” marked “21” and “30” on the chart below. If, once you are dark adapted, you can see only one of the “Guardians,” then your skies are limited to magnitude 2 stars and brighter – very poor. If you see both, but no other stars in the Little Dipper, then your limit is magnitude 3.

On our chart below, the magnitude of each star is listed as a whole number so as not to put decimal points on the chart because they might then be confused with faint stars! So when you see a star listed as “21” that means “magnitude 2.1.”

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

Even in good, dark skies the other four stars in the Little Dipper may not be that easy to see – and the faintest ones may require averted vision – that is, don’t look exactly where the star should be. Instead, look a little to one side or the other, and the star may pop into view. That’s because the center of your eyes are not as sensitive to faint light as the outer regions of your eyes.

Here’s another little trick that may help you locate these faint stars – use binoculars. With typical, hand-held binoculars you may be able to fit all four stars of the Little Dipper’s “cup” into the same field of view. If not, get the “Guardians” in your field of view, then move just a little to where the other two stars of the “cup” should be. This does not count, of course, for the light pollution test. For that test we’re trying to determine the faintest star you can see with the naked eye. But looking first at the stars with binoculars helps assure you that they really are there! You also can trace out the handle this way, though you will have to move your binoculars to do so.

If you can locate all the stars in the Little Dipper with your naked eye, you have very dark skies – congratulations. To see how good they are – and continue to test your eyesight and dark adaption – look for the stars marked “55” and “60” on our chart.

The star marked “60” is traditionally thought of as the faintest you can see with your naked eye. That’s a magnitude 6 star. In really pristine skies, such as those over Mauna Kea in Hawaii, experienced observers with excellent eyes can detect stars down to magnitude 8 with the naked eye. Personally, I’m happy when I can see all the stars in the Little Dipper and especially happy if I can get that “55” star – I’ve never seen the “60” one with my naked eye. But relative to the heavily light-polluted eastern seaboard of the US, I have dark skies.

This is not simply a good guide to light pollution in your area. It also is a handy guide to tell you just how good  – how “transparent” – the skies are on any given night – and to show you how well you have dark adapted at any given moment. So whenever I go out to observe I frequently glance at the Little Dipper to test both my developing night vision and the clarity of the skies. (It never fails to amaze me how much and how quickly my night vision changes. )

To the casual observer all clear nights are equal. But the experienced star gazer knows they are not, and the stars in and about the Little Dipper are a good guide, especially in the summer months when they are so high in the sky.

Events, June 2014 – Bright Lights Along the Ecliptic this Month

This is a great month to become familiar with the ecliptic in our sky. The ecliptic is the plane of our solar system where you will always find the Sun, Moon, and Planets.

Finding it sounds simple – and it is if you pick your time and date. The problem is it changes constantly because the Earth is tilted on its axis and revolving around the Sun.  I should stress one more thing – the ecliptic is not the path you will see the Sun, Moon, and planets take across the sky in a given night – it is the path they will follow as they change position over days, weeks, and even years. How quickly an object follows this path depends on how close it is to us – the Moon makes it completely around the ecliptic each month, the Sun each year – but a distant planet, such as Saturn, takes about 30 years.

You can trace the portion of this path visible about an hour after sunset on a June night in 2014. For the chart below I chose June 13th simply to include a nearly full Moon in the picture. It will, of course, change position each night – but the planets will stick pretty close to these general spots all month. So go out an hour or so after sunset and start your search by looking to the northwest for brilliant Jupiter. It will be brighter than any star, or any of the other planets and only about 10 degrees above the horizon – ten degrees can be measured by holding your closed fist at arms length.

Jupiter thus achors the western end of the ecliptic. We’ll move eastward to trace out the rest of it.

Click on this chart to get a much larger version. (Prepared from Starry Nights Pro screen shot.)

Click on this chart to get a much larger version. (Prepared from Starry Nights Pro screen shot.)

 

Up above Jupiter are the famous Gemini Twins – the nearer and slightly brighter one is Pollux, the other is Castor.

Turn a bit south of west you will find the bright star Regulus. While it outshines most other stars visible tonight, it is just in between Castor and Pollux in brightness and is about 30 degrees above the horizon – three fists.

Next on our list is the red planet Mars – the second brightest object on our chart. If you’re not detecting the rusty redness of it, try looking at it in binoculars. Then compare it with the next bright star on our chart, Spica. Spica is a  little lower than Mars an quite a bit dimmer. (Mats is four fist high, Spica about three and half.) Spica, however, is a very hot – and thus very blue – star. Look at the difference in color between it and Mars.

Moving eastward you’ll find Saturn, whose beautiful rings will show in even a small telescope. However, to the naked eye and binoculars Saturn simply looks like a bright star – not as bright as Mars, but certainly brighter than Spica. It has a pale, yellowish hue.

Continuing to the east is Antares, just 15-degrees – a fist and a half – above the horizon.  It’s name means “rival to Mars” and for good reason – it is a classic, red star, rivaling the color of Mars.  Again, contrast its color with that of Spica and Mars.

Oh – high overhead is the bright star Arcturus. It’s about as bright as Saturn and nearly 70 degrees above the horizon – seven fists.  Do you remember how to find Arcturus? You “follow the arc” of the Big Dipper’s handle – now high in our northern sky, to Arcturus, then “drive a spike” to Spica.

What else is going on this month?

Well, two dates to keep in mind:

The Summer Solstice is June 21 at 6:57 am EDT – and thus begins the longest day of the year.

On June 24 a thin crescent Moon will be very close to the brightest of planets, Venus in the eastern sky about an hour before sunrise. Should be a pretty sight and a nice picture opportunity.

Look East in June 2014 and see if you can make the stars “pop!”

How can we make the stars pop out of the sky and into our mind’s eye?

That’s the perennial problem for me, for what we actually see is so much less than what is actually there that we can’t help but belittle the stars unintentionally. This month’s guide star, Deneb, is a prime example. It’s easy to spot using our chart as it rises in the northeast below and to the left of Vega. In terms of our bright guide star list, Deneb’s rather dim – 19th in the list of brightest stars we see with the naked eye. But that reveals much more about our point of view than about Deneb. Deneb, plain and simple, is one of the most luminous stars in our galaxy. Vega, just above and to the right of it in the northeast, looks so much brighter – but it isn’t. It’s simply so much closer. Vega is just 25 light years away.

Deneb, by one the most recent calculations, is 1,425 light years from us. (This is still open to debate and some put it nearly twice that far away!) But we’ll use the 1,425 light year figure. Put Deneb in Vega’s place – just 25 light years away –  and it would be visible in broad daylight! Does that help it “pop?”

When astronomers talk about how “luminous” a star is they don’t mean how bright it appears to us in our night sky. They mean how bright it actually is. In fact, frequently they use “luminous” to include all the radiation that comes from a star – even radiation in wavelengths that we don’t see, such as infrared and ultraviolet. They then compare a star’s luminosity with the luminosity of the Sun – the Sun being “1.” When they examine Deneb that way they get a luminosity of 54,400 Suns – awesome! (Popping yet? Can you imagine our Sun being twice as brght as it is? three times a bright? How about 54,400 times brighter?)  But when we look at Deneb we see a star that is just moderately bright – magnitude 1.25.

Prepared from Starry Nights Pro screen shot - click for larger version.

Prepared from Starry Nights Pro screen shot – click for larger version.

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

OK – let’s get serious about this popping business. When you look at Deneb, you have to use your mind’s eye to see it for what it really is, not just for what it appears to be. So what should we see when we look at Deneb? First we should see something huge. Deneb is classed as a “supergiant.” So sit back and try to imagine a star whose diameter is 108 times that of the Sun. No, wait! First imagine how big the Earth is. Then get in your mind the fact that the Sun is 109 times the diameter of the Earth. Got that? Now try to imagine that Deneb is to our Sun what our Sun is to the Earth. birdshotBut wait! I really do not want to talk about diameters. Those are for people who live in a flat world. Think in terms of volume, because that’s what a planet or star really is – a volume – a mass formed into a sphere. To get your mind around volume, picture the earth as a tiny bird shot just 2.5mm in diameter. Here’s one to give you the idea. Now picture a sphere about 10.5 inches in diameter – a basketball would be close, or this glass garden globe. See the difference? When talking diameters, the Sun is 109 Earths. But when you’re talking volume, you could fit well over a million Earths inside the Sun. sun_deneb Now think about the same thing in terms of Deneb. That little lead shot is our magnificent Sun. The blue globe is Deneb! That’s what you should see in your mind’s eye when you watch this month’s guide star rise in the northeast. Were Deneb our Sun, its surface would reach halfway to the orbit of Earth and needless to say, Earth would be in a hopelessly hot location. But there’s more, of course. Size is a great starting point, but it doesn’t equate with mass. A lot of stars are bloated – that is, their mass is spread out over a large area and they have a huge surface area from which to radiate a tremendous amount of energy. That is the case with Deneb. It is believed to be about 10-15 solar masses, but its total luminosity – the total amount of energy it radiates when compared to the Sun is a whopping 54,400 times that of the Sun! Wrap your mind’s eye around that! That’s why astronomer/author James Kaler writes that Deneb is

among the intrinsically brightest stars of its kind (that is, in its temperature or spectral class) in the Galaxy. If placed at the distance of Vega, Deneb would shine at magnitude – 7.8, 15 times more brightly than Venus at her best, be as bright as a well-developed crescent Moon, cast shadows on the ground, and easily be visible in broad daylight.

Deneb is unusual for supergiant stars for it is of spectral Class A – that means it’s your basic white star and very hot as stars go. Other very large stars, such as Betelgeuse, are in a different stage of development and quite cool and red to the eye. Deneb is believed to be just 10 million years old. That’s very young in terms of star ages. Our Sun is believed to be 5 billion years old. Deneb will never get to that ripe old age. Massive stars such as Deneb live in the fast lane, burning up their core hydrogen fuel relatively quickly. Kaler gives this analysis:

The star is evolving and has stopped fusing hydrogen in its core. However, it’s hard to know just what is going on. It might be expanding and cooling with a dead helium core and on its way to becoming a red supergiant, or it might have advanced to the state of core helium fusion. Having begun its life as a hot class B (or even class O) star of 15 to 16 solar masses just over 10 million years ago, its fate is almost certainly to explode sometime astronomically soon as a grand supernova.

Kaler certainly knows what he’s talking about, but don’t bother to keep a “death watch” on Deneb. “Astronomically soon” means some time in the next 100 million years or so ;-) Sherlock Holmes once chided his companion Watson saying “you see, but you do not observe.” With the stars, we have to take our cue from Holmes. We have to go beyond merely seeing. And in truth, we have to go beyond merely observing. We have to take the knowledge the scientists have given us and somehow apply it to what we see, so with our mind’s eye we truly observe. Only then can we pop Deneb out of that “twinkle, twinkle little star” category and see it for what it really is.

Vital stats for Deneb (DEN-ebb), also known as Alpha Cygni:

• Brilliance: Magnitude 1.24; its luminosity is the equal of 54,400 Suns. • Distance: 1,425 light years • Spectral Types: A2 supergiant • Position: 20h:41m:26s, +45°:16′:49″

Guide star reminder

Each month you’re encouraged to learn the new “guide” stars rising in the east about an hour after sunset. One reason for doing this is so you can then see how they move in the following months. Deneb and the Northern Cross join several other guide stars and asterisms in the June sky. Again, if you have been reading these Posts for several months, be sure to find the stars, asterisms, and planets you found in earlier months. Early on a June evening these will include, from east to west, the following: Deneb, Vega, Arcturus, Spica, Saturn, Leo’s Rump (triangle),  the Sickle, Regulus, the Beehive, and in the northwest getting near the horizon, Pollux and Castor. You may also see Capella very near the horizon. For more experienced observers looking to extend their knowledge of the skies this month, I highly recommend trying to track down two more asterism – the Northern Crown and the KeystoneOK, technically the Northern Crown (Corona Borealis) is a constellation. But I always apply the name to the handful of moderately bright stars that look like a half circle – a crown. As the chart below shows, these two asterisms are located on a line between Arcturus and Vega and they sort of divide that line into thirds. As with our guide stars and other asterisms, they will help you if you advance to finding other more interesting objects int he night sky with binoculars and telescope.

keystone-crown

For a printer-friendly version of this chart, click here. The Crown itself can provide you with an interesting test of how dark your skies are since a couple hours after sunset on a June night it is well up in your eastern sky. It consists of a circlet of seven stars which can just fit within the field of view of wide-field binoculars – the example below shows an eight degree circle. It may be helpful to look at these stars with your binoculars, even if they don’t all fit in the same field of view at once. But to test how dark your skies are – and how transparent they are at the moment – wait until your vision is dark adapted, then see how many of these stars you can see. The numbers beside the stars are the magnitudes in decimals as given by Starry Nights software. However, I’ve followed the convention of not using a decimal point, since it might be mistaken for another faint star. So “41” means magnitude 4.1, for example. If you are seeing all seven stars you can be happy with your skies and these light-polluted times. In a truly dark location, however, this will be easy – but sadly such locations are rare these nights.

Read text above for explanation of how to use. Thenc lick on image to give you a larger view and luse the link below to download a printer friendly version. (Made from Starry Nights screen shot.)

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

Look North in June 2014! See the ‘North Sky Triangle’ !

Click to enlarge. (Prepared from Starry Nights Pro screenshot.)

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

Yep, that’s Deneb, the guide star that is the subject of our “Look East” Post for June, gracing our “Look North” chart as well. In fact, besides Polaris we have three key guide stars in our northern sky every June, each of which is noted for, among other things, just how far north it is.

Of the three, Capella may be the hardest to find, for it is very near the horizon in the northwest around sunset. But if you have a clear horizon in that direction, you should still pick it up, especially at the start of the month. More prominent, however, are Deneb and Vega. These stars play the key role in one of the best known sky triangles – the Summer Triangle, but that triangle becomes easier to see next month and it will be in the eastern sky. For June it is fun to link Deneb and Vega with Polaris in what we’ll call the North Sky Triangle – and the linkage has some special meaning.

We just happen to be lucky to be living in an era when we have a bright star near the North Celestial Pole – Polaris. There’s no such bright star near the South Celestial Pole, and in other eras there is none near the North Pole either. But in the distant past – and in the distant future – Deneb actually will be the bright star nearest the pole – not as near as Polaris, but still a good general guide to it.

gyroscope precessionThat’s because the Earth wobbles as it spins on its axis in much the same way as a spinning top does. So the axis of the Earth doesn’t always point to the same place. It slowly makes a great circle around the northern sky, taking roughly 25,000 years to complete. Right now our axis is pointing to within a degree of Polaris. Not precise, but good enough so it is a ready indicator of true north. A mere 18,000 years ago Deneb was within 7 degrees of the pole and will be again around the year 9800!

This wobbling of the pole is really kind of mind boggling. I look at Polaris now, and it’s a bit short of 42 degrees above my northern horizon. But in a mere 14,000 years, Polaris will be almost straight over my head, and guess what will be the pole star then? Not Deneb, but its brighter – in our skies – companion, Vega. Of course none of us is likely to witness that event, but it’s still food for thought and gives us a sense of the majestic rhythms and time frame of the heavens.

And speaking of that time frame, as I write this it occurs to me that 14,000 years really feels like a very long time from now – while the 10-million-year age of Deneb doesn’t seem that long – and it isn’t, astronomically speaking. I’m not talking now about what your mind tells you about those numbers. I’m talking about your emotional reaction to them. I wonder if it’s similar to mine? This isn’t idle speculation. It’s central to our appreciating what we are seeing. But I think 14,000 sounds like a long time because it’s a number that fits into our day-to-day experience. Huge, but we can easily imagine 1,000 of something.  So imagining 14,000 of something comes easily to us. But few of us have any experience with one million. It would take about 11 days to count one million seconds and no one in his right mind is about to try it. So when we speak of the 10-million-year age of Deneb, or the five-billion-year age of the Sun, the numbers lose their emotional impact because they don’t relate easily to our experience. But 14,000 – well, we know, in an emotional sense, just how long that is!

Events May 2014 – Four Easy Planets, Two Challenge Planets, and a Meteor Storm Watch

Click picture for larger image. (Created from a Starry Night Pro screen shot.)

Click picture for larger image. (Created from a Starry Night Pro screen shot.)

May skies have a lot to offer in 2014, for in addition to the usual parade of stars, we have four easy planets to spot, two challenging planets, and a possible “meteor storm,”  one of those once-in-a-life-time sky spectaculars -maybe! There are also a couple of special events for sky watchers in the Southern Hemisphere. Here’s the summary with  links to the details.

Mercury – the Big Tease!

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

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

Mercury is notoriously difficult to see, mainly because it demands that you know exactly when and where to look – and while you should see it with your naked eye and really quite easily, it’s much easier to find with binoculars first.  It also plays this kind of dual game with us. The first part of the game is to be so close to the Sun that it is almost always drowned in the glare of the Sun – even after sunset. (Don’t even think of looking for it with binoculars before sunset – if you accidentally catch the Sun in binoculars you will do permanent damage to your eyes.)

Start looking for Mercury 30 minutes after sunset when – from May 16 to May 28  – it will be a fist or more above the western horizon. That gets it away from the worst of the haze near the horizon and into a sky that is starting to get dark. In the next 30 minutes the sky will get darker – making it easier to see Mercury – and Mercury will get lower, making it more difficult to see.

In addition to this little game, Mercury is actually getting higher in the sky from May 16 to about May 25 – but it’s also getting dimmer – and while it’s still quite high by May 28, it is also more than a full magnitude dimmer than it was on May 16. See why I call it a tease? But you will find it, and when you do, you’ll say “that’s easy!” Yep, if you look on the right night, in the right spot, at the right time, and have an unobstructed western horizon that is also clear, Mercury is a piece of cake! ;-)

Here are a couple more charts to help out – note the changes in brightness and background stars even over just a week.

mercury51914

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

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

Why is Mercury behaving this way? It’s actually getting about 25 million miles closer to us during the last two weeks of the month. However, like Venus, Mercury goes through phases which can be seen in a telescope as it approaches us because it’s also starting to go between us and the Sun. This means it changes from a disk to a crescent, so while it gets closer – which would mean brighter – there is also less of it seen by us as it moves towards becoming a crescent. So it gives us a double whammy – after the 25th it starts getting closer to the Sun and it also continues to dim.

Storm, Shower, or Drizzle – this could be really cool!

There’s some big news on the meteor front that may result in a very exciting – and ultimately unpredictable – special event in the early  morning hours of May 24th. It’s summed up nicely in the headline from the cover of the May Sky and Telescope which contains an excellent article on the subject.

‘Meteor Storm Watch – Dark with a Chance of Fireballs’

OK – that got my attention. I’ve always been fascinated by those old woodcuts depicting the incredible 1833 Leonids meteor shower. I think they’re a bit exaggerated, but that one apparently really was exceptional.

1833Leonidmeteors

This month we have a short-period comet that may produce a spectacular show for us – but not as a comet. This is Comet 209P/LINEAR and it is scheduled to cross the orbit of Earth and be totally unspectacular, even though it is quite close to us as comets go, you will need a good size telescope just to see it.

 But . . . several expert meteor observers are predicting a sudden meteor shower on the morning of May 24, and if you’re in North America above roughly latitude 40 you are at the right location to have a front row seat should this shower develop. And don’t despair if you’re in the southern US – there still could be some beautiful fire balls for you.  Some meteor experts even are predicting a possible meteor storm – something I have never seen, but would sure love to. And, of course, it may be a total fizzle, or it may be the sky spectacle of a lifetime. . . but cloudy!  You just can’t know – and that sense of anticipation and mystery is what makes these sorts of things extra fun.

Now what does a meteor shower have to do with a comet? Everything.

Meteors are pebble size or smaller generally.  When we run into one going 67,000 miles an hour – that’s our speed in orbit – they collide with our atmosphere much faster than a speeding bullet and almost always burn up before they reach the ground.

 Think about it for one moment.

Imagine something about the size of a pencil eraser 50 miles away and yet burning so brightly that you can see it. Think of whether or not you can see someone strike a match 50 miles away – or see the glow of a cigarette.  That gives you some idea of the speed these things hit with and the tremendous heat that is generated as they collide with our atmosphere.

 Now think about a Comet. Pig Pen, of Peanuts fame, is the best model I can think of for a comet – like Pigpen, a comet leaves a trail of dust behind it. That trail of dust doesn’t go away. It falls off the comet but continues to orbit the Sun. And like Pigpen’s perpetual dust cloud, it just hangs there, like droplets of water in a spacecraft – each grain of sand in its own private orbit about the Sun.

Every August 12 the Earth crosses a trail of dust left by Comet Swift Tuttle. We pass through it and we see lots of meteors, and we call this the Perseids meteor shower. If you catch it at its peak on a dark, moonless night, you may see as many as one meteor a minute.

They are called the Perseids because if you traced each meteor trail backwards, you would see they were all appearing to come from the same part of sky – a small area in the constellation of Perseus. Think of it as an open window that lets the dust of Comet Swift Tuttle tumble through.

In December there is another such shower called the Geminids. These happen every year as well – in fact, there are several more such showers, but the Perseids and the Geminids are seen as the best – most active – of the bunch.

The event this May is more complicated. I don’t know quite how they figure all this, but apparently this little, very dim, unspectacular comet has been laying down trails of dust as it goes around the Sun every five years or so. As one of the experts explains it in the May issue of Sky and Telescope, “all of the trails ejected between 1803 and 1924 cross Earth’s path on May 24.” That’s 25 trails of comet rubble all hitting at about the same time.

They know this precisely enough so that four of the experts are in agreement that this will happen right about 3 am EDT on the morning of May 24.  But they do warn the predictions could be off – generally they think this will be as good, or better, than a Perseids meteor shower. But they also grant that it may be a dud.

 The event is well-timed and placed for those of us in the northern tier of states. Those in the southern states may get a good show from especially bright meteors – but far fewer of them. The rest of the world will pretty much miss out.

 Remember, when there’s a shower, the meteor can appear anywhere in the sky, but you trace them back to their radiant – which in this case will be in the obscure – very obscure – constellation known as Camelopardalis. You all know what a Camelopardalis is, right? I’ll help you. Think giraffe. It’s in the northern sky at 3 am on May 24. To learn more about this area and see a chart, go to my post here. 

Consolation Prizes for the Southern Hemisphere

If you live south of the Equator, May always offers one of the better meteor showers of the year for you, the Eta Aquarids on May 4, 6, and 7th. A few of these may sneak north as well.

Also on the evening of May 13-14 the Moon will be near Saturn for most of us, but for folks in New Zealand and much of Australia the Moon will cross in front of the planet – what is called an occultation. This is cool to see in a telescope, but what I love is the pictures I’m sure it will generate showing Saturn near the edge of the Moon. Seeing Saturn close to the Moon, even in a picture, is a special treat that really drives home the difference in distance. Saturn, which with its ring system is so large that it would actually fill the space between us and the Moon, will look tiny next to our little moon because it is so much more distant.

On the East Coast of the US, Saturn will get within only a couple of degrees of the Moon that night – but as you move west, it gets closer – close enough to catch the two in a low power telescope field in the early morning hours.

And then there’s Uranus and Venus

I was hoping that Venus would guide binocular users right to Uranus, but no such luck. The two will be very close on the night of May 15 and 16, 2014, making it easy for small telescope users to find Uranus – but this will happen in morning twilight, and Uranus will be too faint to see against twilight background with ordinary binoculars. In fact, I think it’s going to be a challenge in a small telescope. The chart below is for an hour before sunrise – at that point Venus is only seven degrees above the eastern horizon. While it should be easily visible, assuming clear skies, spotting Uranus about 10 magnitudes fainter, won’t be easy both because it is so low and because of morning twilight.

To get both in view you need a telescope that will gather some extra light, yet also provide a 2-degree field of view, which is why I consider this a challenge – but fun to try if you enjoy mornings, as I do.

On the morning of May 25th you won’t need anything special to appreciate the Venus show – then you’ll have a beautiful crescent moon just a few degrees above Venus!

 

Look North: May is the month the North Star gets two bright flankers!

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

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

Is the North Star – Polaris – our brightest star? No! And it certainly won’t look that way this month as it shares the northern sky with two very bright stars. But, read on. Polaris is not nearly as dim as it looks!

If you have been learning your guidepost stars as they rise in the East, you won’t be surprised by the two bright stars which flank – and outshine – our pole star in May. To the northwest is Capella, a star we first met when it rose in the northeast in November. In May the northeast is dominated by a star that is almost Capella’s twin in brightness, Vega, a guidepost star we introduce in May. (See “Look East!” for more about Vega.) As a bonus we also have the twin guidepost stars, Castor and Pollux, making their way into the northern sky high above Capella. But let’s focus on Capella and Vega.

New star watchers frequently assume the North Star, Polaris, will be the brightest star in the sky. It isn’t even close! It is bright, but its fame comes because it’s very, very close to where the axis of the Earth points to the north celestial pole. So it serves anyone trying to find true north as a very good guide. But when it comes to brightness, it’s in the same league as the stars in the Big Dipper. Quite bright, but it can’t hold a candle to Capella and Vega. When you look at a list of the brightest stars, Vega is number 5 and Capella number 6. Polaris, our North Star, is number 48!

As simple as one, two, three!

That doesn’t mean Polaris is a slouch, though. First, in the eastern sky in May you meet Spica. (That’s on our chart for the east.) One distinction of Spica is that it’s as close to being magnitude 1 as any star gets. A distinction of Polaris is, as Spica defines magnitude 1, Polaris defines magnitude 2. (To be precise it’s magnitude 2.02.) Vega and Capella are extremely close to magnitude 0. Vega is 0.03 and Capella 0.08. Good luck on telling the difference! This month, if you look north 90 minutes after sunset, you may think Capella is a bit brighter actually – but if it appears that way it will be because it’s a bit higher in the sky and thus is not dimmed by having to fight its way through as much of our atmosphere as Vega is doing at the moment. So don’t try to split hairs. And yes, you’re right – they are NOT really as “simple as one, two, three” – on the magnitude scale they are as simple as zero, one, two – but that doesn’t sound as good! (Vega and Capella are zero; Spica is magnitude one, and Polaris, magnitude two.)

So which is really the brightest star of these four? Are you ready for this? Polaris! That’s right – if you put all four stars at the same distance, Polaris would appear to be the brightest. Remember, that the lower the magnitude number, the brighter the star. In absolute magnitude – the brightness we give to a star if they are all shining from the same distance  – these four stars line up this way:

  • Polaris -3.4
  • Spica -3.2
  • Capella 0.1
  • Vega 0.3

And those absolute magnitudes also reflect their order in distance from us.

  • Polaris 433 light years
  • Spica 250 light years
  • Capella 45 light years
  • Vega 25 light years

So sometimes a star is very bright because it’s – well, very bright. But sometimes it only appears to be very bright because it is very close to us. If you put our closest star into this group, our Sun – remember, it is just 8 light minutes from us – in absolute magnitude it would be by far the dimmest of this group – absolute magnitude 4.9! So while Polaris doesn’t look all that bright, it really is a very bright star! Another way to think about this is if you move our Sun out to where Polaris is, it would be about magnitude 10! You would need binoculars or a telescope to see it!

Click image for larger view of this chart. Yellow circle represents typical field of view for low power binoculars, such as 10X50.

To get an idea of the difference between Polaris and our Sun, point your binoculars towards Polaris.  You should be able to make out the “Engagement Ring” asterism – granted, a crude ring with Polaris as the diamond.  This asterism points you towards the true north celestial pole  – just avery short distance to the other side of Polaris –  and also gives you a good idea of about how far Polaris is from that pole.  Small binoculars will not show you the companion of Polaris, but to get an idea of how bright our Sun would be at the same distance, look for the star labelled 9.8 – and if you can’t see it, see if you can see the star that’s a bit brighter labelled “9.”  Don’t expect to see these instantly. Sit calmly, relax, and keep looking for at least a minute.

And here’s one more cool secret about Polaris. It has a companion that just happens to be quite dim – magnitude 9. It’s fun to see the two of them if you have a small telescope, though it’s not all that easy because Polaris is so much brighter than its companion. But if you get a chance to see Polaris and its companion in a telescope, remind yourself that the very faint companion is still a bit brighter than our Sun would look at this distance. This companion, known as Polaris B, was discovered in 1780 by William Herschel, and for many years Polaris was thought to be a binary star – that is, a system of two stars orbiting about a common center of gravity. But Polaris was holding one more surprise – it’s really a triple star.

The top image shows Polaris and its faint companion that can be seen in any decent backyard telescope. The bottom image shows the second companion, Polaris Ab, which has only been seen by using the Hubble Space Telescope.

This has been known for some time, but no one could see the third star until they turned the Hubble Space telescope on it in 2006. That’s when NASA released the first image of this third companion. The accompanying press release explained it this way:

By stretching the capabilities of NASA’s Hubble Space Telescope to the limit, astronomers have photographed the close companion of Polaris for the first time. They presented their findings  in a press conference at the 207th meeting of the American Astronomical Society in Washington, D.C.

“The star we observed is so close to Polaris that we needed every available bit of Hubble’s resolution to see it,” said Smithsonian astronomer Nancy Evans (Harvard-Smithsonian Center for Astrophysics). The companion proved to be less than two-tenths of an arc second from Polaris — an incredibly tiny angle equivalent to the apparent diameter of a quarter located 19 miles away. At the system’s distance of 430 light years, that translates into a separation of about 2 billion miles.

“The brightness difference between the two stars made it even more difficult to resolve them,” stated Howard Bond of the Space Telescope Science Institute (STScI). Polaris is a supergiant more than two thousand times brighter than the Sun, while its companion is a main-sequence star. “With Hubble, we’ve pulled the North Star’s companion out of the shadows and into the spotlight.”

So as I said, Polaris is no slouch. It not only is a very bright star, but it also has two companions, and scientists are still studying it because it is unusual in other respects. We’ll talk about those other differences another month.

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