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    My Journey through the Astronomical Year

    Think of this as a "companion text" to this, the main web site. Not required reading, butI hope you'll find it interesting and helpful.

Look North! Oops – there’s a big hole in the sky!

Well, not really – but unless you live in an area with very dark skies, free of light pollution, you’re going to have a hard time seeing the faint stars above Polaris, the North Star, at this time of year. Here’s what our March north sky star chart looks like.

Our northern sky is quite dark above Polaris, but the Big Dipper is prominent in the northeast and serves as our primary guide to finding the North Star. Click image for larger view. (Prepared from a screen shot of Starry Nights software.)

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

Notice the emptiness? The area labeled “Dark Hole?” Mind you, this is not a black hole – just an area of our sky that looks quite empty – unless your viewing location is free of light pollution and your eyes are thoroughly dark adapted. If you can see all seven stars of the Little Dipper, then you should see several stars in this area. But even then I doubt if you will be able to trace out the constellation which goes there. It’s known as Camelopardalis. My copy of Urania’s Mirror, published in 1832, says Camelopardalis consists:

. . . of 58 stars, but none larger than the fourth magnitude. . . .The Camelopard is an Abysinnian animal, taller than the elephant, but not so thick. He is so named because he has a head and neck like a camel, and is spotted like a leopard; but his spots are white upon a reddish brown ground. The Italians call him giraffa. To Hevelius, who formed the constellation, he owes his celestial honors.

Ah, giraffe! Thank you, Italians. Here’s how he is pictured in full color on one the constellation cards that came with Urania’s Mirror (The scan is © Ian Ridpath.)

Camelopardalis as depicted on the card from Urania's Mirrror, 1832. Notice the Pointer Stars of the Big Dipper are near the upper left and Polaris is just to the right of the giraffe's head, so at this time of year the giraffe would appear upside down in our northern skies.

If you put him in the sky at this time of year his head would be down near Polaris. . . . Hmmm… the illustrator seems to have forgotten the spots mentioned in the text, and the animal’s neck got a bit longer than a camel’s. Ah well – while the 1830s had some advantages in terms of simplicity, I don’t think I would like to be trying to learn the night sky with Urania’s Mirror as my only guide.

Oh – but speaking of long necks, one of the things that has always fascinated me is some of the early attempts at astronomical telescopes and particularly the one in the following woodcut. This was an instrument built by Johann Hevelius in the mid-17th Century at his observatory in Poland. The tube was about 150 feet long – befitting, in a strange way, for the man who put a giraffe in the northern sky!

Click image for larger view.

Look East! March 2010 roars in like a Lion – with Saturn tagging behind!

March roars into our eastern night sky like a lion – Leo, the Lion that is, led by the Little King “Regulus” and in 2010 brings Saturn with it. Just ahead of it is a special binocular treat, M44, a veritable beehive of stars barely visible to the unaided eye. Think of it as the lion’s whiskers. And don’t forget to look for the zodiacal light!

Leo does look much like the Lion depicted inthe 1603 Bayer catalog.  Click image for larger version.

The stars of Leo do indeed trace out some key parts of the Lion depicted in this plate from the 1603 Bayer atlas. (Click image for larger view.) Note that the bright star that marks the tail is named "Denobola," which in Arabic really does mean "tail." We encounter this also in the tail of Cygnus the Swan where the bright star is named "Deneb." The Arabic star names are frequently descriptive. (Image courtesy of Linda Hall library of Science, Engineering and Technology.)

 

I don’t usually put an emphasis on constellations, but in March it is fitting, for it makes it easy to remember what it is you see in the East just after sunset and besides, this is one of those constellations where when you connect the dots it looks something like it is supposed to look.

In fact, in my mind’s eye I can see the classic lion of the old Bayer star charts, but I more often see two very easy to remember asterisms – the Sickle that forms Leo’s head and mane, and the Triangle that forms Leo’s rump. And Regulus, our new bright guidepost star for this month, means “little king,” or “prince,” in Latin. That fits right in with the lion‘s reputation as King of the Beasts. And what a lovely image to have a prince leading a lion onto the night-time stage this month! Here’s our eastern sky chart. (As usual, click the image for a larger version, or download a printable version.)

Click image for larger view. Use link below to download a printer-friendly version. (Chart developed from Starry Nights screen shot.)

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

If you look in the same spot an hour or so later – or wait until mid-month, you will get the special treat of seeing Saturn, a favorite target for small telescopes, though this month it will be a tad disappointing to telescope users. Right now Saturn’s rings appear tilted as seen from Earth so that they make a thin line extending out from either side of the planet. In most years, they are at such an angle that they make a much better display. But Saturn is a special feature for this year, 2010. It won’t be back with the stars of Leo for another decade. So lets get on to the prime star in the east that’s there every year at this time, Regulus.

Is Regulus memorable in its own right? Well yes. It’s a star that is spinning so fast that if we could see its disc, it would look like a beach ball that someone sat on. It takes Regulus about 16 hours to make one rotation – in comparison our Sun, a smaller star, takes about a month to rotate. In fact, if Regulus were spinning just a bit faster, it would spin itself apart!

The rapid spinning gives Regulus an equatorial diameter that is about one-third bigger than its polar diameter. This also results in the polar regions of Regulus being much hotter than its equator.

Regulus is also a multiple star system, but as such rather dull visually. The second star in the system is much fainter, so it can barely be detected by a skilled observer using binoculars – and in a telescope it’s so far away from the primary star that they don’t seem like a pair at all. Both the primary and secondary are spectroscopic doubles – meaning the companions are so close we can’t see them with a telescope.

Though a relatively young star – about 250 million years as compared to the five billion year age of our Sun – Regulus is apparently nearing the end of its normal life as a “main sequence” star. That is, it’s about to finish burning hydrogen, which means it will soon go into the last stages of its life. But according to Jim Kaler, Regulus is also a curious case. It appears to have a very close white dwarf companion which scientists believe once was much larger and brighter than Regulus. But the gases were drawn from the white dwarf into Regulus making it both huge and bright and causing it to spin the way it does.

In total, Regulus is another example of how what looks like a common star to us, is quite fascinating when seen in the light of modern science.

Vital stats for Regulus:

• Brilliance: Magnitude 1.35, 22nd among the brightest stars in our sky; shines with the luminosity of about 150 Suns.
• Distance: 77 light years
• Spectral Type: B7V
• Position: 10h:08m:22s, +11°:58′:02

The buzz about the Beehive (M44), Mars, and Leo’s whiskers

In ancient times the constellation Leo extended much farther east and west, and M44 was considered to be its whiskers.

from “The Next Step – Finding and Viewing Messier Object” by Ken Graun

Whiskers indeed! I like that. It’s a great way to remember where to look for M44, for if you can find the Sickle – the huge head and main of Leo – then all you have to think is “now where would his whiskers be?” Scan 2-3 binocular fields in that direction – westward – and you should soon stumble upon M44, the Beehive. In 2010 this is especially easy. Start at Regulus and scan towards Mars, one of the brightest objects in the sky. M44 will be along this path, much nearer to Mars than to Regulus. Here is a chart you can use to find it – and to map the changing position of Mars, which will be especially interesting in March.

Following Mars and finding M44, the Beehive - or if you like, Leo's whiskers! Click chart to see larger image. (Chart developed from Starry Nights screen shot.)

Click here to download a black-on-white (printer-friendly) version of this chart that you can also use to chart the movements of Mars.

Over the next couple of months Mars will serve as a bright beacon making it easier to locate M44 whose other names are “the Beehive,” and Praesepe, which is Latin for manger. And if you have dark skies, away from light pollution, you will see this as a small, wispy cloud, perhaps suggestive of Leo’s whiskers. It is, in fact, a beautiful star cluster as binoculars or a small telescope will reveal. Galileo first discovered its true nature and in this hazy patch discovered more than 40 stars. You should see about that many with your binoculars. This is one of the nearest star clusters to us, and although there is still debate over its exact distance, it is around 580 light years. That compares with about 400 light years for the Pleiades. The two clusters are pretty close to the same size, but M44 is considered much older. M45 – the Pleiades – is estimated to be 78 million years old, while M44 is thought to be about 660 million years old. As star ages go, they’re both quite young.

The Latin name, Praesepe, is worth examining because it explains the names of two relatively bright stars which flank it – Asellus Borealis and Asellus Australis. Borealis means “northern” and Australis means “southern.” Asellus means “ass” – as in donkey – and Praesepe means “crib” or “manger.” In other words, the Beehive apparently looked to some like a pile of hay in a manger and these two flanking stars were donkeys, eating that hay, one to the north and one to the south. In binoculars the scene should look something like this screen shot from Starry Nights software to which I’ve added labels.

M44 and surroundings as it would appear in binoculars with a 5-degree field of view. Click image for larger view. (Chart derived from Starry Nights software screen shot.)

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

The two donkeys are about as bright as the stars in the handle of the Little Dipper, so under dark skies should be faintly visible to the naked eye with the northern one the dimmest. The third star, Eta Cancri, is dimmer still. Its name, however, indicates that it, the Beehive, and other stars shown here are all part of the rather obscure constellation known as Cancer, the crab.

There’s a revealing naked eye exercise buried here as well. This is a good month to chart the course of Mars across the background of stars. Mars starts out the month appearing to run away from the Beehive – that is, it’s moving westward against the background of stars. Then, just before mid-month it appears to stand still for a couple of days as it reverses direction and starts to come back towards the Beehive (eastward) as if tugged by an invisible cord. In April it will skip right by, missing the Beehive by less than a degree and passing between the Northern Ass and the Southern Ass.

Keep in mind that all this happens over a period of days and weeks, and to see it you need to carefully chart the position of Mars against the background of stars on several nights. This sort of exercise helps you appreciate great observers who charted the heavens before the invention of the telescope. It also helps you understand how puzzled early observers were by the apparent behavior of Mars and why this had them scratching their heads for centuries trying to make sense of these movements in a universe where Earth was at the center of everything. During any given night, of course, everything appears to move westward because of the rotation of the Earth. The movement we’re interested in here is the revolution of Earth and Mars around the Sun.

It’s much easier today – with a sun-centered solar system – to understand why Mars first appears to move in one direction, then the other. This is caused simply by Earth overtaking Mars as the two planets orbit the Sun at different distances and speeds. Here’s where the planets are in mid-March, courtesy of John Walker’s “Solar System Live” online orrery.

Click image for larger view.

See the Zodiacal Light

Finally, don’t forget to look for the zodiacal light this month – especially if you missed it last month.

You don’t need a totally clear horizon to see the zodiacal light, or binoculars, but you do need total darkness and that means little-to-no light pollution. I feel I have a good shot at it from my favorite ocean-front observing point where I have a clear horizon to the west with no cities to create light domes there. Moonless evenings in February, March, and April – and mornings in September and October – are the best time for folks at mid-northern latitudes to look for this subtle phenomena. In March 2010 that means to look about 80 minutes after sunset on a clear night between March 1 and March 15.

For more detailed information on this, see the February posting here.

Events-February 2010 – Happy Valentines Day Jupiter – we’re onto you!

Ah, to be romantic in mid-winter!  And this year, on February 14th, we have Jupiter  – king of the gods – being joined by Venus – goddess of love, beauty, and fertility –  beside the soft glow of a slim crescent moon! Is that appropriate, or what? (OK, we’ll ignore the fact that Jupiter is married to Juno.)  The question is, will we be able to see this little tryst? Or will it be so close to the horizon – and the Sun – that it will remain a figment of our imaginations. One thing I’m sure  of – it will be a challenge. Other challenges this month for naked eye and binoculars include:

Jupiter, Venus, and the Moon

Sky and Telescope describes this encounter this way: “Venus and Jupiter appear 2 degrees apart on February 14th, when an ultraslim young Moon joins them in a tight formation.”  Yep! “ultraslim” is right. When I asked Starry Nights Pro to show me this scene I couldn’t even see the moon it was so slim! That’s because I’m on the East Coast. West Coast observers will see a moon that’s a bit older – and thus larger – so they will have a better shot; but I’ll try. Here’s the screen shot from Starry Nights for 15 minutes after sunset at my latitude, about 42 degrees north.

Click image for larger view. Printer-friendly version linked below.

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

If you want to see this live, you first need an unobstructed western horizon. Then, a lot of luck in terms of no clouds. If you meet those two requirements, then a good pair of binoculars, or a small telescope would be handy. Be careful though – make sure the Sun has fully set before you start looking. I plan to wait 5 minutes, then I’ll start scanning the horizon. I expect to pick up Venus first.  Jupiter will be a bit higher, but also dimmer, so it should pop out second and be in the same binocular field of view as Venus. I expect the moon will be last to put in an appearance, but if I put Venus to the left side of my binocular field, I should be able to pick up the Moon on the other side.

Normally, of course, Venus and Jupiter are easy targets – downright dazzling. But now we’re talking about finding them in bright twilight and very near the horizon. Thirty minutes after sunset Venus will be barely one degree above the horizon – that’s about the width of your pinky held at arm’s length – without gloves!  And Jupiter will be about three degrees above the horizon. Venus sets just 38 minutes after the Sun and Jupiter about 50 minutes. See why it’s going to be hard to surprise these celestial lovers?

But if you get clouded out, don’t despair – they actually get closer during the next couple of days, though the moon will quickly rise much higher and so not be an intimate part of the picture. Now if it’s clear enough to see these three – or even two of them, then I’m going to wait another 50 minutes to see if I can detect the elusive zodiacal light.

See the Zodiacal Light

Now this is something much different. You don’t need a totally clear horizon to see the zodiacal light, or binoculars, but you do need total darkness and that means little-to-no light pollution. I feel I have a good shot at it from my favorite ocean-front observing point where I have a clear horizon to the west with no cities to create light domes there. Evenings in February and March – and mornings in September and October – are the best time for folks at mid-northern latitudes to look for this.

The zodiacal light is roughly the same intensity as the Milky Way, so if you can see the Milky Way from your chosen location, then you should be able to pick up this faint glow.  Like the Milky Way, it stretches over a good deal of sky. It is widest near the horizon and gets narrower as it rises towards the zenith.  You want to look for this roughly 80 minutes after sunset. You can check for an exact time for your location by getting information from here on when astronomical twilight ends. (The drop-down menu on that page specifies the times for astronomical twilight.)  As astronomical twilight ends you want to start looking. As with any faint object, your eyes need to be dark adapted, so I am assuming you have been out for at least 15 minutes with no white light to dazzle you. If you try to look for this earlier, you may confuse it with twilight. Much later and it is not as bright, for what we are seeing is sunlight reflecting off  interplanetary dust particles – dust particles that orbit in the same plane as the planets – the area we call the zodiac – and thus the name for this phenomena, zodiacal light.

If you see it,  reflect on this explanation from Wikipedia:

The material producing the zodiacal light is located in a lens-shaped volume of space centered on the sun and extending well out beyond the orbit of Earth. This material is known as the interplanetary dust cloud. Since most of the material is located near the plane of the solar system, the zodiacal light is seen along the ecliptic. The amount of material needed to produce the observed zodiacal light is amazingly small. If it were in the form of 1 mm particles, each with the same albedo (reflecting power) as Earth’s moon, each particle would be 8 km from its neighbors.

For the metric-challenged (that includes me) that means one dust particle every five miles! And that causes all that light?! Awesome!

Watch the bright Asteroid Vesta dance through Leo

This spring you get a chance to follow one of the brightest asteroids as it dances about the constellation Leo. This will be particularly easy to find with binoculars on the night  of February 16 (February 17 UT) , or the night before or after that one.  The fast-moving asteroid will be close then to the second brightest star in the easy-to-spot asterism of Leo’s Sickle. To find this, look east about three hours after sunset. Here’s what you should see with the naked eye.

Click image for larger version of this chart. Chart was developed form Starry Nights screen shot.

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

Once you are sure you have found Gamma Leo, then look at it in your binoculars.  You should see something like what is shown in the circle, though your binoculars may show a somewhat larger field. What is neat here is that Vesta is moving right between Gamma and 40 Leonis and it will take it about three nights to complete the journey.  You can start looking for Vesta earlier, however, if you want. It will enter the field of view shown at the lower left about February 7. And it will leave the circled region, exiting to the upper right, on about February 25. It would be fun to spot it on several nights and use the printer-friendly chart, linked below, to mark your own observations of its movement.

Click image for larger view. Printer-friendly link below. (From Starry Nights screen shot.)

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

Catch the Demon in Demise

I wrote about Algol the “Demon Star” in the posting for October, but it’ s still well placed for viewing in February, and if you look at the right time, you’ll catch it in mid-eclipse, which is cool.

Every 2.3 days Algol dims like clockwork, but it is only at its dimmest for about two hours, so to see it in this condition you really need to be watching at the right two hours. Fortunately, there are several places that will give you a list of times when this occurs – but many of them will be while normal people are sleeping – and many more will be during daylight hours. However, each month there should be one or two dates when it is really a good time for you to catch Algol doing its thing.

Most of the listings I know of for Algol “minima” give date and time in Universal Time. What I like about the one at Sky and Telescope magazine, is it will calculate a list of coming Algol minima for you – and give you the Universal Time, plus your local time. So it’s easy to glance over it and see when it will be most convenient – weather permitting – for you to take a look. In my case, February 2010 gives me a couple of opportunities worth noting:

  • 02/07/2010 @ 09:45 pm
  • 02/10/2010 @ 06:35 pm

You can learn much more about the minima of Algol – and get specific predictions for any date with translations to your local time  by visiting this page at Sky and Telescope.

Look East! February 2010 brings two dogs and an impostor!

We have two “dog stars” on the eastern horizon early on February evenings  – and in 2010 an imposter that nearly outshines them. To see all three, look low in the east about 45 minutes to an hour after sunset – they will be the first  objects visible in the twilight. Together the three make a nice line of bright “stars” from due east to southeast. What’s more, each of the “dog stars” has a “pup” we can’t see with our naked eye – a faint companion star orbiting it, which in many ways is more interesting than the stars we do see. The dog stars also complete two handy winter asterisms.  More on all that later.

Click image for larger chart. Use link below to download a printer-friendly, black and white version of this chart. (Chart is based on a screen shot, modified by me, of Starry Nights Pro software.)

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

The bright impostor that is nearly due east is the planet Mars, which at the start of the month is about as close to Earth as it will get in two years, and so about as bright as it will get in that time.  The middle star of the three is Procyon, seventh brightest star in our night sky. And to the southeast and a tad lower than the other two  is  brilliant Sirius, brightest star in our sky, and next to the North Star, Polaris, probably the best known star in the world.

Not only are these two stars very bright, they 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 the southern hemisphere, or the southern part of the northern hemisphere.)

Later – when it is darker and all three (Mars, Procyon, and Sirius) are higher – look for the color contrast between Mars and these two stars. Early in the evening the colors will be confusing because the two stars will twinkle and Sirius, especially, is noted for flashing all sorts of colors. This is simply because it is so bright and it is so low. Any bright star near the horizon is shining through a lot of air, and it is the air that makes it appear to dance and change colors rapidly. Stars are so distant they are point sources of light. Planets are closer and their light comes from a disc, too small to detect with the naked eye, but still making them tend to shine more steadily.

The Big Dog as Johannes Bayer depicted him in 1603. (Image courtesy of Linda Hall library of Science, Engineering and Technology.)

The Little Dog as shown in the 1603 Uranometria chart. (Image courtesy of Linda Hall library of Science, Engineering and Technology.)

Sirius is the best known of the two “dog stars,” but it actually rises a little later than Procyon, for those in northern latitudes.  Sirius is known as a “dog star” because it is the brightest star of the 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, you can see that no amount of 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” 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, a class of stars far denser than anything we encounter on Earth.  In fact, to appreciate this, let’s take a close look at our own Sun.

Sirius - with Sirius B at lower left. Click image for larger view. Credit: NASA, H.E. Bond and E. Nelan (Space Telescope Science Institute, Baltimore, Md.); M. Barstow and M. Burleigh (University of Leicester, U.K.); and J.B. Holberg (University of Arizona)

The Sun is a ball of gas, but even that idea is hard to grasp because we think of gas as something light and wispy, yet gas in the Sun reaches densities that 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 as dense as 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. 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.

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 Lyre.  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 others – 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.)

Greater Asterisms

Sirius and Procyon join with Betelgeuse to form the “Winter Triangle,” an asterism of three bright stars that appears in the southeast just as the Summer Triangle stars, Vega, Deneb, and Altair, are bowing off stage to the northwest. I have to admit, though, I’ve never paid any attention to this. If you find it useful, great. If not. . . . well, consider the Winter Hexagon.

The Winter Hexagon is an asterism I love, but to see it requires that you have been learning the guidepost stars for the past few months. If this is your first month on the job, wait until next year. But if you are familiar with these stars from past months, note what a wonderful, huge Hexagon they create, encompassing  a part of the sky that is just afire with bright stars. The Hexagon stars are: Sirius, Rigel, Aldebaron, Capella, Castor/Pollux, and Procyon. Yes, it takes seven stars to make up this six-sided figure because I choose to fudge it a bit and count Castor and Pollux as one point.  (Others just use Pollux, but I have trouble separating these twins.)  The star chart for the Winter Hexagon and Winter Triangle looks like this.

Click image for larger view.

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

Notice that we not only have seven bright stars anchoring this asterism, but there are at least half a dozen bright stars inside it.  I think this large concentration of bright stars is one of the reasons why we think of winter nights as clearer than those of summer.  Truth is, summer nights can be just as clear, but they don’t contain such a dominant concentration of bright stars. For those with binoculars and small telescopes, some of the most fascinating objects are near, or inside this Hexagon, including the Pleiades, the great Orion Nebula, and the spectacular open clusters in Gemini and Auriga.

Vital stats

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 -1.46,  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.)
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