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.)

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:

• See the zodiacal light (February 1-14)
• Watch the bright Asteroid Vesta dance through Leo ( All month, but February 15-17 best )
• Catch the Demon in Demise (Check for best dates for you.)

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 North: It’s February and the Great Bear is stretching

About one hour after sunset, look north and you should see a sky similar to the one shown in our chart – assuming you live at mid-northern latitudes. 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.  As a bonus this month, you might look for the Great Bear. At this time of year I picture him coming out of his cave and stretching  – clawing his way up the sky to the northeast. To see what I mean, look at the classic representation of him below the chart.

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

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

Used by permission from the Linda Hall Library of Science, Engineering & Technology found here

This is how Johann Bayer, a lawyer and an amateur astronomer, pictured the Great Bear in his “Uranometria,” a breakthrough star atlas published in 1603.  Notice that the Big Dipper is a relatively small, but bright part of this constellation. Also notice that Bayer’s bear has a long tail – very un-bear-like. Still if you study the northeast sky on a February night, you should be able to make out the bear’s head, and at least one front paw and one back paw. For me it really does feel like a great bear is clawing his way up into our sky.

Look north: It’s January and “W” is now an “M”

About one hour after sunset, look north and you should see a sky similar to the one shown in our chart – assuming you live at mid-northern latitudes. 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.

Click image for larger view. Chart derived from Starry Nights Pro screen shot.

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

Early on a January evening the Little Dipper appears to be pouring into the Big Dipper. The “Guardians of the pole” – the two bright stars at the cup end of the Little Dipper – are low in the sky and the Big Dipper is skimming along the northern horizon.  For me it is hidden by trees and obscured by the light dome of a shopping mall in that direction.

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

January 2010 events: Meteors, Mars, and the Moon skims the Pleiades

The Quadrantids are the best meteor shower I’ve never seen!

No kidding. The Quadrantids are tie with December’s Geminids for generating the most number of meteors per hour and will peak on January 3 – but there are several reasons why I’ve never gotten a good look at them and I’m afraid this year, while giving us a chance to see some, will not be good, particularly for observers in the United States.  That said, I still plan to watch this year. Meanwhile, the  dominant naked-eye planet this month is Mars which gets as close as it will come for the next couple years – and thus will appear dazzling to the naked eye and will appear in the  telescope as big  as it will be until 2013. But I have to be honest – that’s not very big and other years it can get brighter.  What will be fun for observers using the naked eye and binoculars this month will be the Moon skirting the Pleiades,  but -  seems like there’s always a “but” this month – the closest approach will come in the early morning hours.

There also are a couple good chances to catch Algol, the “demon star,” in eclipse this month – no  buts about it – so here’s the line up of some special events for January 2010 with links to the details:

• Quadrantid meteors
• Mars
• Moon and the Pleiades
• Algol in eclipse

Quadrantid meteors

The good news about the Quadrantids is there are a lot of them! Meteor enthusiast measure intensity of a shower by what is called its ZHR -  Zenith Hourly Rate.  This is a legitimate figure, but significantly higher than what the typical, single observer will see – still, it’s a way to compare apples with apples – or meteor showers with other meteor showers.  The ZHR for the Quadrantids is 120 and only the Geminids have the same high peak.  The popular Perseids, which come in August, peak out at 90, and right now another popular shower, the Leonids, are in a low and expected to have a peak ZHR next november of 15!

So why have I missed the Quadrantids before? Partly because they come in mid-winter when the weather here in New England doesn’t generate much enthusiasm for lying still on your back and looking up at the sky for an hour or two! But also, this is one of those showers that is seen best in the early morning hours because that’s when its radiant point is highest in our sky – and even then the radiant is only about as high as the North Star, so  given the best of circumstances I will miss some. But also this shower has a sharp peak, while some other showers  stay fairly intense for a much longer time span. So you have to hope that sharp peak comes at a time when the radiant is also high in your sky.  In this case – 2010 – that peak comes at 19 hour Universal Time on January 3. That’s  two o’clock in the afternoon for those of us on the East Coast of the United States, hardly the time to observe meteors. What more the moon, bane of meteor watchers because it washes out all but the brightest ones,  will be just a few days past full.

So my plan is this: I will observe starting about 6 pm EST January 3 – when it is fully dark – and going to about 8 pm when the Moon comes up – weather permitting.

Chart from screen shot of Starry Nights Pro software - click for larger image.

The up side to this timing is that  the shower will be at half strength  – according to the “Observer’s Handbook 2010″ – for about seven hours either side of its 2 pm EST peak. So I will be in a window when the ZHR might be as high as 60 – very respectable.  However, the radiant will be very low in the northern sky at that point – so low that I’ll miss about half the meteors that are available. (The radiant is near the end of the handle of the Big Dipper.)   Throw in light pollution in that area of my sky and my realistic guess is I’ll see maybe one good Quadrantid every three-to-five minutes.  Still, that’s worth a try.

As with all meteor showers, you need patience and some sort of lounge chair is helpful – and, of course, you need to dress warmly. This is a shower that favors northern observers – the farther north you are, the higher the radiant in your sky.  And as always, the meteors may appear in any section of the sky, but if you trace each backwards you will see it seemed to come from the general area of the radiant point and looking in that general area is a good idea. I’ll focus on the region above and around the North Star.

Oh – meteor showers are usually named for the constellation in which their radiant is located,  but in the case of the quadrantids it was named for a constellation no longer recognized as such.

Mars

This is Mars as seen at it's very close approach in 2003 using the Hubble Space Telescope.

As I mentioned last month, Mars and Earth are closest to one another every 2.1 years – but exactly how close they get each time varies over  a 16-year cycle. So we get close every 2.1 years, but you have to examine each close approach and see where it fits in the 16-year cycle.  This means that some close approaches are much better than others, so the best telescopic views of Mars happens every 16 years! And where are we now in that 16 year cycle? Somewhere near the bottom. But play the hand you’re dealt. If you want the best view of Mars in a backyard telescope, then January and February give you the best chance you’ll have for two years and things won’t start to get really better until about 2014.

On the other hand, if you just enjoy keeping track of the planets with the naked eye, Mars is very easy to find this month. Just go out about four hours after sunset and look for the brightest star in the East. Here are charts for my latitude – 42 degrees north – showing what I will see when looking east, four hours after sunset, on January 1, 15, and 31 respectively. Notice that Mars is higher in the sky as the month goes on? And if you look closely at the pair of stars just to the left (north) of Mars you’ll notice Mars is changing its location relative to the background stars. The changes  you are seeing are a result of the motions of Earth and Mars around the Sun.

Looking east four hours after Sunset, in January from my location in Westport, MA. All charts were made using screen shots from Starry Nights Pro software. I simply added the labels.

Mars will rise earlier each night and be a bit brighter, but even at its brightest will still be outshone by Sirius, the brightest star in our night skies. Sirius is to the right, relative to the charts above, roughly as high in the southeast or south as Mars is in the east. It’s easy to identify because except for the moon, it is the brightest thing in the sky at that time. (Jupiter is brighter, but sets quite early.)

Here are the key numbers and dates for this apparition of Mars, according to Sky and Telescope magazine:

• Mars will appear larger than 10 seconds in diameter right through March – that’s big enough to see some features in a backyard telescope.
• In late January it comes closest but will still appear to be only 14.1 arc seconds in diameter at its largest – on a really good year, such as 2018, it will appear to be over 24 seconds in diameter.
• In 2012 – when we get another close look – it will actually be a tad smaller at its best because it will be a little farther away.

When I get a "good" look at Mars in my telescope I usually see something like this.

What should you be able to see? Frankly, not that much. But it’s still fun to try. With a good telescope and good astronomical “seeing” conditions, you should be able to make out some features on Mars such as the northern polar cap, and large, irregular olive drab splotches that stand out against an orange background. Is this exciting? YES! It really is because you are seeing it live and for me, nothing beats live observing. But it’s also good to have realistic expectations.

Moon and the Pleiades

So the Moon will be  close to the Pleiades on the nights of January 24 and 25 – and real close the morning of January 25, 2010 – so what?

Here’s what.  We usually think of the Moon – and the Sun – as being much larger in our sky than they actually are. When either are near the horizon they look huge. But at any time they are really so small that they can be covered by a finger tip held at arm’s length. In fact, 11 full moons could fit between the two “pointer” stars in the cup of the Big Dipper!  On the other hand, we usually think of the Pleiades as appearing quite small in our sky. But the Pleiades cluster is actually twice as large as the Moon and you can prove this to yourself when you watch the Moon approach this famous star cluster. Seeing them both with your naked eye – or better yet, both in the same binocular or low-power telescope field – is really quite astonishing.  We don’t get this opportunity too often,  so that’s why this event is worth noting. It drives home the fundamental truth that the moon covers just half a degree in our sky – which coincidentally is the same amount that our Sun covers which is why the Moon can eclipse the Sun for us.

The best time to see this is between 4 am and 6 am EST on the morning of January 25.  (The closest approach is at about 11 hours Universal Time, January 25.) That’s when the Moon nearly touches the Pleiades.

Algol in eclipse

I wrote about Algol the “Demon Star” in the posting for October, but it’ s still well placed for viewing January 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,t here 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 list 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, january 2010 gibes me too such opportunities. The first is January 10, 2010 at  10:32 UT. That translates to 5:32 am January 10 for me in the Eastern Time Zone.  Since I habitually get up early to observe winter mornings, that’s great.  The second opportunity for me comes on January 21, 2010 at  21:49 UT, which translates into 4:49 pm  EST on the same date. That’s right about sunset for me on that particular date, but that’s no problem. It will still be near minimum an hour later as it becomes dark enough for me to see it and the comparison stars. And as the sky continues to darken I can watch Algol slowly get brighter.

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

Look East: January brings a feast of twins and giants!

January brings a host of bright and wondrous winter stars. There are four new guidepost stars to meet this month and one new guidepost asterism, Orion. Orion is probably the best known figure in the heavens because it actually looks like a person and can be seen from most locations in the world because it’s centered on the celestial equator. That’s a lot for one month, but fun to think about on a dreary winter day and more fun to observe on a brilliant, winter evening.

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 image for larger version. 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 January eastern sky – what to remember

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

Castor – A trio of twins

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

Click image for larger view.

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. But there is more, much more, to Castor.

Were you to look at Castor in a backyard telescope, you would see it has a twin – another bright star that appears quite close – so the two are Castor A and Castor 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 one bright star is really the combined light from six stars, all held together in one of the most complex star systems we know.

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

• Brilliance: Magnitude 1.58, the 23rd brightest star in our sky. Absolute magnitude is 0.9.
• Distance: 45 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

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.” 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 no where 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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Betelgeuse – a giant among giants

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 won’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. 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 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 Betegeuse is the Alpha. Of course, Betelgeuse, being variable, may have been brighter when Johann Bayer made his designations in 1603. Baer’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.”

Vital stats:

• Brilliance: Magnitude 0.12, the 7th brightest star in our sky (sometimes). 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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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.

Orion - as seen when rising in mid-northern latitudes. (Click for larger image.)

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!

Orion, as seen when rising in the east from Sydney, Australia. (Click image for larger version.)

The real point here is 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 in your sky to your north. In the northern hemisphere it appears to make an arc in 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 you’re 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 they 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

Prime Time Observing for December 2009 – take the Subaru Challenges!

“Subaru?”  Yep! That’s the Japanese name  for a little purse of celestial gemstones better known in the West as the “Pleiades,” or in many cultures throughout the world as the “Seven Sisters” or some variation of that idea.  And  yes, I said “challenges” – plural, because there are two:

1. how many Pleiads can you see with the naked eye?
2. and can you see – with naked eye, binocular, 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! And yet all that “cold” blue light really indicates they are very young, very hot stars, all of which are part of an open cluster. But more on that in a minute.  For while the Pleiades lead the observing agenda for any December, in 2009 we have some other great choices as well, including a splendid meteor shower and four nice planets to view – five if you want to get up early. And we’ll add the Pleaides “follower”  - the huge reddish star, Aldebaran – to our list of guidepost stars as well.

So let’s take a look at this month’s prime time chart – a chart that applies to the eastern sky as seen from mid-northern latitudes, 45 minutes after sunset as usual, but with this quibble – you  may not see the Pleiades that early. If you don’t, try locating November’s guidepost star, Capella, in binoculars and sweeping south (to your right), or locate Aldebaran, and sweep upwards with your binoculars. The Pleiades should pop into view. If you still don’t find them, just wait, they’ll appear as the sky gets darker. In any event, you’ll want to wait until later if you’re going to take the challenge. So here’s the chart with our new star, Aldebaran, front and center. Yes, Aldebaran – an Arabic name which means “the follower” and refers to the way this star seems to follow the Pleiades across the sky – and who wouldn’t!

Also, we’ve added a “kite” asterism with Capella – last month’s guidepost star now highinthe northeast – as the dominant star int he asterism. (This is actually the classic constellation Auriga, the Charioteer, but I think the Kite is easier to see and remember.)

Click image for larger view. (Chart derived by modifying Stary Nights Pro screen shot.)

Click here to download  a black-on-white version of the preceding chart, suitable for printing in landscape format.)

OK – here are the highlights we’ll be covering this month:

• The Pleiades makes a challenging sight for naked eye observation – how many can you count? And they’re a delightful sight in binoculars or small telescopes  – but can you see the nebulosity?
• The Geminids meteors should put on a terrific show with no interference from the new moon on December 13-14.
• We draw closer and closer to Mars as we chase it down in our orbit around the Sun and this makes it both brighter to our naked eye and bigger in our telescopes.
• And speaking of telescopes, great Jupiter, dropping low in the southwest, has its third and last – for several years – close encounter with Neptune.
• And yes, Saturn is back for early risers with rings that are becoming much easier to see again in asmall telescope!

The Pleiades (Subaru) challenges

Even without binoculars, the Pleaides – also known as “M45″ and “the Sevens Sisters” -  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. A recent 6-year-old visitor to Driftway Observatory saw them – as many adults do – as the “Little Dipper.” Well the six brightest stars do form a tiny dipper, but the real Little Dipper isn’t nearly as dazzling, is much larger, and is in the north, not the east.

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 – less than 50 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.

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 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 2009 your first opportunity for this will  be around December 5 or 6th.  The Pleiades will be well up about two and a half hours after sunset, and the Moon will not have risen at that time.  As the month progresses, you can wait later and later without interference from the Moon because the Moon rises later each night until New Moon. (And later is better because the Pleiades will be higher in the sky.) Until  about December 19 or 20th – by then the Moon is in the western sky when you look – far away from the Pleiades, but still likely to make it difficult to see the faint stars and nebulosity.  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 its constantly changing position and brightness wash out the sky anywhere near it.  But as you can see, there’s a solid two-week window when you can take the Pleiades challenge in the middle of this month – assuming the weather cooperates! And, of course, the Pleiades will still be with us through the winter.

Some helpful charts

Click image for larger version. (This chart is derived froma Starry Nights Pro screen shot. A printer firendly version appears in the links which follow.)

There are three printer-friendly charts listed here, but for starters I suggest you download only the first two. They both show the brightest Pleiads but the second one has no names on it and is meant for you to use – and add to  – when taking either challenge.  Put it on a clipboard and take it, a pencil, and a soft red light to your observing location.  Then when you spot something you can mark its location in relation to the brightest stars. Once you’ve done this, take a look at the third chart which shows the Pleaides 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 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,

The Geminids show December 13-14

Click image to get an enlarged version. (Modified from Starry Nights Pro screen shot.)

(Download a printer friendly version of the preceding chart. )

This is a terrific meteor shower because unlike the Perseids in August and the Leonids in November, you don’t have get up at 3 am for a good view – though for East Coast observers  midnight is best this year, though plenty of meteors should be seen earlier. The radiant point for this shower is in the constellation Gemini and it is already above the eastern horizon as it gets dark.  By about four hours after sunset it is well up in the east. Since the meteors appear to radiate from this point – and you can see them anywhere in the sky – then at this stage more than half the shower meteors should be above the local horizon. So it is really worth it to start looking as early as 7 pm on December 13.

However – there’s always a however – the shower this year is due to peak at 5 hours Universal Time. That translates to midnight EST December 13/14. So my personal plan is to start looking for these meteors at 11 pm and keep looking until 1 am EST.  That gives me the best opportunity to see the most meteors, assuming the weather cooperates.

Here are some tips to get the most out of this shower no matter where you are and when you look:

1. Look up – constantly! Geminid  meteors can appear in any section of the sky – it’s just if you traced them backwards they would seem to come from one area near the constellation Gemini.  (Yes, you’ll see more most likely if you look in the general direction of the radiant point, but you may miss some too, so don’t hesitate to look around at other sections of sky.  When I say “look up” I’m not being facetious. Meteors wait for no man or woman – and there’s no instant replay. I’m amazed at how many meteor watchers don’t follow this simple rule – they talk to companions, and seem to look around at or near ground level, and then grumble when someone else spots a brilliant meteor that they missed.

2. An adjustable beach chair or lounge is great, as well as a sleeping bag or blankets. Even in warm climates, you get cold sitting still for an hour or more under a clear sky.  You’re just one big radiator sending off heat to the universe!

3. Bring binoculars and when you see a bright meteor, use them! Look where the meteor just appeared and you are likely to be rewarded by seeing the trail of smoke it leaves. You may be able to watch this for several seconds as the winds in the upper atmosphere start to twist and disperse it.

Finally, just enjoy being out there. The stars of winter are especially brilliant, not because the skies are clearer and drier (in the northern hemisphere they may be) but because there are simply more bright stars, especially in the region around the constellation Orion, which can be see from just about anywhere on Earth.

Chasing Mars

Here’s the thing – Mars and Earth are closest to one another every 2.1 years – but exactly how close they get each time varies over  a 16-year cycle.So we get close every 2.1 years, but the closest approach happens about every 16 years. This means that some close approaches are much better than others, so the best views of Mars happen every 16 years! And where are we now in that 16 year cycle? Somewhere near the bottom. But play the hand you’re dealt. If you want the best view of Mars in a backyard telescope, then the next four months offer you the best chance you’ll have until about 2014. (In 2012 it will actually be a little worse than this time.) On a positive note, this time Mars is relatively high in the sky for Northern Hemisphere observers and its fun for naked eye observers to just trace its path among background stars. This chart provides you with a starting point for Mars in mid-December.

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

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

Mars will change constantly in December. Each night it will rise earlier and be a bit brighter, doubling in brightness from the beginning to the end of the month – but still outshone by Sirius.  Its position against the background stars also changes. For most of the month it appears to move in the general direction of Regulus. However, on the 21st it stands still, then starts to move in the opposite direction – westward. This is called “retrograde” motion and is caused by our overtaking it as both planets orbit the Sun.

Here are the key numbers and dates for this apparition of Mars, according to Sky and Telescope magazine:

• Mars will appear larger than 10 seconds in diameter from December through March – that’s big enough to see some features in a backyard telescope.
• In late January it comes closest but will still appear to be only 14.1 arc seconds in diameter at its largest – on a really good year, such as 2018, it will appear to be over 24 seconds in diameter .
• In 2012 – when we get another close look – it will actually be a tad smaller at its best because it will be a little farther away.

What should you be able to see? Frankly, not that much. But it’s still fun to try. With a good telescope and good astronomical “seeing” conditions, you should be able to make out some features on Mars such as the northern polar cap, and large, irregular olive drab splotches that stand out against an orange background.

Jupiter’s close encounter with Neptune

Jupiter has had three close encounters with Neptune this year – this is the last. (To read about the first, see this post.)  While Mars is a target for late evening viewing, Jupiter needs to be seen early in the evening, for it sets earlier each night. With a telescope you can start viewing 45 minutes after sunset.

You can find Neptune reasonably near it – using a telescope – all month, but it will be closest during the few nights around December 21st. This changes rapidly, so even if you are a few days either way Neptune quickly gets lost in the background of stars of similar brightness. But on or near December 21 it will be less than one degree away from Jupiter and you should be able to fit both planets in the same field of view if you are using  a low-power, wide-field eyepiece. But keep in mind, at magnitude 8, Neptune is significantly dimmer than Jupiter’s moons.

As a bonus, the crescent Moon is just five degrees away, above the two planets, on December 21. Here’s a finder chart for December 21, 2009 showing Jupiter and Neptune as seen in a low-power telescope view with the image flipped left-to-right, which is what you will see when using a telescope thathas a diagonal mirror. With a reflecting telescope the image also will be flipped AND upside down.

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

To download a printer friendly version of the preceding chart, go here.

And Saturn?

The ringed planet – and yes, it’s rings are tilted to us now in such a way that they are again easy to see in a small telescope – is an early morning treat in December.  Although it rises just before midnight at the end of month, it’s not above the horizon until nearly 4 am at the outset. My advice – get up early – about two hours before sunrise. Our chart’s for that time at mid-month and at that time Saturn is well placed in the southeast for telescopic observation. It is one of the brightest “stars” in that section of the sky and easy to pick out with the naked eye.

Click image for larger version. Starry Nights Pro screen shot with annotations added.

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

Prime Time observing for November 2009

November brings us  our southern most – and northern most – guidepost stars,  Fomalhaut and Capella – as well as a nice meteor shower for early risers and, of course, the continuing dance of Jupiter’s moons.

I’ve also introduced two new features which should become a staple  – a downloadable black-on-white version of each chart  so printing one for use outside doesn’t drain all your color ink.  The second feature is to include on the chart a summary of the information worth remembering about each guidepost star. It’s much more fun if you really know a star – that is, what makes it distinctive – and not simply know how to find it.

For northern hemisphere observers Fomalhaut is the guidepost star we see for the least amount of time – and Capella is the one we see the most. In fact, for many Capella is visible  during some hours  every night of the year – and for those north of latitude 45 degrees it is circumpolar – that is, it never sets. But lonely – and newly fascinating  – Fomalhaut just puts in a relatively brief appearance low to the south.  That’s where we’ll start with a finder chart for Fomalhaut. Like our other finder charts it is centered on 45 minutes after sunset for mid-month, but should be useful throughout November.

Click chart for a larger image. (Chart modified from screen shot of Starry Nights Pro software.)

(Click here to download  a black-on-white version of the preceding chart, suitable for printing in landscape format.)

Hubble image showing debris ring that surround Fomalhaut.

Fomalhaut is “lonely” because there are few bright stars in its vicinity. It is now of special interest because early in this century the Hubble Space Telescope got a fantastic picture of a disc of “debris” surrounding it, showing this young star to be in the throes of forming planets. Then in 2008 scientists announced they had actually found a planet circling Fomalhaut, the first planet outside our solar system to be seen with visible light. Cool! Add to this that Fomalhaut is a neighbor, just 25 light years away,  and in this photograph could be easily mistaken for Sauron of Lord of the Rings fame and Fomalhaut becomes quite memorable.

Finding Fomalhaut

As always, it’s easiest if you start looking  in the southeast 45 minutes after sunset when in the twilight only the brightest stars are visible as shown on our chart. Fomalhaut is the brightest STAR south of southeast and about a fist and a half above the horizon 45 minutes after sunset. I emphasize “star” because in 2009 Jupiter is in the vicinity further south, significantly brighter, and about twice as high.  Trailing well behind Fomalhaut – to the east – and lower still is a second magnitude star (same brightness as the North Star) called Deneb Kaitos. It’s about the same distance from Fomalhaut as Fomalhaut is from Jupiter and I mention it only so you won’t mistake it for Fomalhaut.

If you have learned the Great Square – see this post – then the two stars that form the western edge of that square can be used, as shown in our chart, as pointer stars. Drawing an arrow through those two stars leads you to Fomalhaut. You could also wait until a couple hours after sunset when you would find Fomalhaut very close to due south. Even then, from my latitude of 41.5° N it is not quite two fists (19°) above the southern horizon.

Ahhh Capella!

Capella is distinctive because it’s not “a” star – its two! But these two, bright, yellow suns are so close together that you’ll always see them as one, even if you use a large telescope. Together they make a star that rivals Vega and Altair , now well into our western sky, in brightness. (see Summer Triangle chart here.) In fact Capella is the third brightest star in the Northern Hemisphere – but that’s a tad deceptive because it doesn’t count Sirius – the brightest star that most Northern Hemisphere observers can see, because technically Sirius is in the Southern Celestial Hemisphere, since it is below the celestial equator.  But you don’t have to worry about such technicalities to enjoy a view of Capella. Just use the chart below which shows the view to the Northeast 45 minutes after sunset on November 15, but generally good for the entire month. You will need a very clear horizon, however, especially at the start of the month because then Capella will not even be one fist above the horizon.

Click chart for a larger image. (Chart modified from screen shot of Starry Nights Pro software.)

(Click here to download  a black-on-white version of the preceding chart, suitable for printing in landscape format.)

Capella is really a complex multiple star. It’s two main components are both yellow giants dubbed Aa and Ab, but there are two more stars in this family. However, they are a pair of red dwarfs only visible in a telescope and are so far away from the two bright stars that they take more than 1,000 years to complete an orbit. The two bright stars orbit in just 104 days.  James B. Kaler, in his book The Hundred Greatest Stars, says this about the Capella twins:

These two magnificent giants are separated by about the distance between Venus and the Sun. A resident on a ‘Jupiter’ ten times further out would see two ‘Suns’ about half a degree across (similar to the Sun in our own sky) , separated at maximum by some 6 degrees, one setting right behind the other.

So when you find Capella pause – picture yourself on the Jupiter-like planet with these twin yellow Suns in your sky!

Finding Capella

It’s easiest to find Capella if you start 45 minutes to an hour after sunset. Choose a spot with a clear horizon to the Northeast and watch for a bright star to appear very near the horizon. Like all bright stars near the horizon, Capella will twinkle and flash in different colors because you are seeing it through a lot of atmosphere. It won’t show its soft, golden hue until it is much higher in the sky.

For me Capella marks a graceful arc of  bright stars and asterisms that circle the north celestial pole.  If you have been following these directions for a few months, look at Capella, the Bow of Perseus, and the “W” pf Cassiopeia to see what I mean. Watching these move in the course of a single night – or from month to month – always gives me a real sense of how, from our vantage point, all the stars appear to circle Polaris. Other stars and asterisms introduced in previous months that are still readily seen include  the Summer Triangle of Altair, Deneb, and Vega, whichis high over head and crossing into the western sky. Arcturus is just above the horizon in the west, the Big Dipper just west of northa nd hugging the horizon, and the Teapot is diving intot he ground in the southwest.

Dancing moons . . .

Jupiter is in its prime on these November nights, and gets as high as you’ll see it this year when it crosses the meridian roughly 45 minutes after sunset, which is when I suggest you start your observing if you’re tying to learn the brightest stars. It’s also a good time to turn a good pair of binoculars towards Jupiter and see if you can spot any of its four Galilean moons.  These are easily bright enough to see in binoculars, but there are two problems. First, the glare of Jupiter can drown them out (they will look like faint stars very near the planet and roughly in line with its equator) and second, you need to hold your binoculars very steady.  Your best chance would be with 10X50 binoculars steadied against the corner of a building, or fence post, or whatever.

In September there was a special event where the four moons were all hidden at once. This post starts with that event, but gives lot more details about Jupiter’s moons. You might want to review it. Or, you  may just want to know which of Jupiter’s moons is where on any given night. In that case  use this neat little online utility provided by Sky and Telescope magazine.

. . . and “falling stars”

Now that's a meteor shower!

The best meteor shower I ever saw came several years ago when early one morning Bren and I dragged some pillows and sleeping bags to the upstairs deck and tried to count the Leonids. Oh, it wasn’t like this old woodcut shows. That was a real shower and must have been something to behold. And sadly, the Leonids this year – at least for North American Observers – will not put on a great show, but you’ll certainly have a chance to see more meteors than usual.  Besides, November mornings can be refreshing and there are lots of other things in the morning sky this month, so why not take a peek – treat the unusual number of meteors you wil see as frosting on the cake!

The drawing on the right depicts the Leonid meteor shower of 1833  – as remembered 50 years after the event! I don’t believe the drawing is literal, but I do believe this was an extraordinary meteor shower.

When and where

The shower is predicted to peak on November 17,  at 4 am EST, or 9 hours Universal Time.

Look anywhere in the sky – though the meteors you see should trace back to a spot in the constellation Leo in the Eastern sky at that time. This spot is called the radiant and mared on the chart below. But don’t expectt o see meteors here. You’ll see them justa bout anywhere in the sky.

And yes, you may hear predictions about sharp, fantastic spikes with hundreds of meteors an hour. This is true, but these  spikes will be brief and they will come at a time that favors Asia. One prediction puts this peak at 21:43 Universal Time and the other 17 minutes later on November 17, 2009. I’m amazed that we now understand these showers so well that such predictions can be made.

. . . and what else?

But back to the morning of November 17, 2009. What can you expect your morning sky to contain, besides some bright meteors? Well, for starters, all the brilliant stars of late winter, but with two nice planetary additions: Saturn will be the bright “star” just one fist above the horizon and almost due east at that time. Well above it will be an even brighter Mars. In fact, the two planets bracket Leo the Lion whose head marks the radiant point for the Leonid meteors. And if you wait until well into morning twilight you’ll see a brilliant Venus rise a bit south of east.

Click image for larger version.

(Click here to download  a black-on-white version of the preceding chart, suitable for printing in landscape format.)

Prime Time observing for October 2009

Seeing a bow, a demon,  and a few hundred billion stars  – meanwhile, Jupiter slams it into forward!

Please note: All charts with this post are for observers in mid-nothern latitudes centered on 40° N. If you are 10 or more degrees south or north of that – or if you’re not sure of your latitude – please go here to make your own custom star charts.

On tap this month is a new asterism,  the bow; a variable, Algol, the “demon star;” a neighboring galaxy you can see with the naked eye or binoculars; and yes, Jupiter, which appears to abruptly change directions as it moves against the background stars.

To begin our monthly exploration of the night sky, you can take a slide down Andromeda’s Couch to Mirfak and the Bow of Perseus in the northeast, assuming you learned these last month. If these are new to you, simply start by looking for the rising low in the northeast.

As usual, go out 45 minutes after sunset and watch the stars emerge. It may take another 15 minutes for  to see the bow  clearly, but what you are looking for is three stars in a vertical arc, with the middle one – Mirfak -  the brightest. How big an arc are we talking about? Just make a fist and hold it vertically at arm’s length, and your fist should just cover these three stars. How high? The bottom one should be about a first above the horizon.  Here’s a chart modified from Starry Nights Pro software..

Click chart for much larger view. If you observed last month you know the Great Square and Andromeda's Couch and can slide down the "Couch" to Mirfak, the brightest star in the bow of Perseus. If this is your first month of learning the sky, simply look to the northeast and find the bow.

Now if you want to be a stickler about mythology, Perseus doesn’t carry a bow – he wields a sword instead, which he is holding in his right hand high over his head, while in the left hand he holds the severed head of Medusa. Here’s how the 1822 “Urania’s Mirror” depicted it.

Perseus - click for alarger version.

Oh boy – and if you can see all that in these stars, then you have a very vivid imagination. I never would have learned the night sky if I had to try to trace out these complex constellations as imagined by ancient cultures and depicted in star guides up until fairly recently.  And for the purposes of helping you find your way around the night sky I think remembering the Bow of Perseus is easier. Mirfak, is just a tad dim to serve as one of our guidepost stars, but it does come in handy when identifying the “Demon Star,” whose proper name is Algol.

Getting sharp about brightness

As you start to learn the stars, it may surprise you how precise you can be about their brightness.  At first you may have difficulty just telling a first magnitude star from a second, but if you get to know Algol, the “Demon Star,” I bet you’ll find that you can quickly become quite sophisticated in assessing brightness and shaving your estimates down to a tenth of a magnitude.

Imagine a star that regularly varies in brightness every few days – that’s what Algol does. Exactly every 2 days, 20 hours and 49 minutes it begins a 10 hour period where its brightness dims more than a full magnitude. If you look during the right two hours, you’ll catch it at or near its dimmest – and most of the rest of the time you’ll catch it at peak brightness. And it’s quite easy to judge. But first let’s find it. Here’s the chart we’ll use.

Notice how Algol makes a very nice triangle with two companions, and all three stars are close to the same brightness – Almach, the bottom star in Andromeda’s Couch; Mirfak, the central star in the Bow of Perseus; and Algol. That brings us to our first challenge: Go out any clear night and study these three stars and decide which is the brightest. Two are equal in brightness, but one is a tad brighter than the other two. Which is it? Algol? Mirfak? Almach? (The answer is at the end of this text so you can ignore that answer until you actually have an opportunity to test yourself.)

However . . .

Because Algol is a variable, sometimes when you look at it, Algol will actually be significantly dimmer than either Mirfak or Almach. In fact, there’s a reasonable chance it will be dimmer than either of Mirfak’s two fainter companions that make up the Bow of Perseus. If when you test yourself, this is the case, congratulations! Make note of the date and time.

Algol is a special kind of variable star known as an eclipsing binary. That is, what looks like one star to us is really two stars, and when we see Algol’s light start to dim it means its companion is passing between Algol and us causing an eclipse. Since the stars are locked in orbit around one another this happens with clockwork regularity.

The above diagram came from this astronomy class web site which includes amore detailed scientific explanation.

Since either star of the pair can cause an eclipse, there is a much fainter, secondary eclipse of Algol – really too faint to be noticed by most observers. Why is one eclipse fainter – because one star is blue, Class B – and much hotter/brighter than the other star which is “K” class. (Remember – OBAFGKM.)  It is when the cooler star is in front that we see the dramatic change in light.

It’s fun to catch Algol in mid eclipse, but I suggest you not read about when to do this right now. Instead, do the little challenge first. Then when you’re ready, go to the final item in this, which explains how and when to catch Algol in eclipse and in the process, tells you the brightness of its companions.

OK – second project – Jupiter changes direction!

I described this in an earlier post an am quotingit in its entirety here.

On October 1, 2009 a nearly full moon joins Jupiter, Uranus, and Neptune in the southeast as shown here about an hour after sunset. (Jupiter is made large to indicate its relative brightness – ut it will look like a very bright star – not a small moon!) This is how the sky appears from latitude 42 degrees north and longitude 71 degrees west. Chart from Starry Nights Pro software. Click for larger image.

The idea here is simple – connect what we can see in the sky this month with what’s actually going on. We’ll do this by watching Jupiter, the easiest object to find right now since it is the brightest “star” fairly high in the southeast shortly after sunset.

With just a few quick checks with binoculars we should be able to track the movement of Jupiter in relation to a bright, nearby star. You should start this project on or before October 1, 2009 if at all possible and plan to observe two or more nights between your start time and October 13. Then observe again in about a week and again near the end of the month.Your first couple of checks should show Jupiter in “retrograde” moving westward among the background stars. Your next two checks should show Juputer has resumed it’s normal eastward movement.

Use the following chart as both your guide and your log. That is, click on it to get a version you can print, take out under the stars, and record your observations on with a pencil.

Click for larger version, suitable for printing.

So why does Jupiter appear to first go one way, then the other? Afterall, it isn’t really doing that, is it? Like the other planets – and us – it’s simply continuing a steady, eastward journey around the Sun. But so are we – and we are moving much faster because we’re much closer to the Sun. So what you are seeing is partly the movement of Jupiter – but also the apparent change in its position caused by our rapidly changing position.

I made the following animation from Solar System Live charts. It shows how Jupiter’s position changes slowly in relation to Earth and the other planets, particularly Neptune. The animation starts with September 1, 2009  and moves a month at a time for six months. The arrow shows our changing view of Jupiter with relation to Neptune, a much more distant – and even more slowly moving, planet. Notice that in late December Jupiter makes another close approach to Neptune – the third this year – which will make especially easy at that time to find this distant and faint planet. Right now you can use the chart above to track it down – it would be just visible in binoculars on a moonless night.

So let’s review the movements we’re dealing with here.

1. The daily rotation of the Earth causes Jupiter to appear to rise inthe east and move westward as the night progresses.

2. The revolution of the Eartha round the sun at a much higher speed than Jupiter makes it so that for some time the huge planet appears to be moving westward in relation to background stars and the more distant planet Jupiter. That apparent westward motion comes to a stop October 13, 2009.

3. Jupiter’s own motion is more apparent after October 13, as it appears to move eastward against the background stars. This general motion will carry it about 30 degrees eastward – very close to where Uranus can be found now – in about a year. It takes Jupiter almost 12 of our years to make a complete circuit of the sky.

The idea here is simple – connect what we can see in the sky this month with what’s actually going on. We’ll do this by watching Jupiter, the easiest object to find right now since it is the brightest “star” fairly high in the southeast shortly after sunset.

See a few hundred billion stars at one glance!

Yes, you can do it if you have good dark skies, you have allowed your eyes to dark adapt, and you are looking at the right place.  Once again, Andromeda’s Couch is our guide, and what we are looking for this time is the Great Andromeda Galaxy aka M31.

This is our “neighbor” in space if you can wrap your mind around the idea that something “just” 2.5 million light years away is a “neighbor.” ( As you try to do that remind yourself that a single light year is about 6 trillion miles – of course, good luck if you can imagine a trillion of anything!)

But seriously, you can see this with  your naked eye – and even in normal, light-polluted skies, you can see it with binoculars. In fact, this is one object where the binocular view can be almost as rewarding as the view through a telescope. Here’s a wide field chart for mid-month and about 90 minutes after sunset. At that point the galaxy should be roughly half way up your eastern sky.

Click image for larger version.

Starting with the preceding chart – and moving to the chart below:

1. Locate the Great Square
2. Locate Andromeda’s Couch off the northeast corner of the Square.
3. Go down to the middle star in the couch, then count up two stars and bingo!
4. You can also find the general vicinity by using the western end of the “W” of Cassiopeia as if it were a huge arrow head pointing right at the Andromeda Galaxy.

Click image for larger chart.

Well, “bingo” if you have been doing this with binoculars. With the naked eye it’s more an “oh yeah – I see it – I think!” But what do you expect? Think about it. The light from the near side of this object started its journey about 150,000 years before the light from the more distant side did! And think of where the human race was 2.5 million years ago when these photons began their journey – or for that matter, where all these stars really are today! Nothing is really standing still -everything is in motion.

You might also want to think about the folks who are on a planet orbiting one of those stars in the Andromeda Galaxy and looking off in our direction. What will they see? A very faint patch – probably fainter than what we see when we look at the Andromeda Galaxy, but in binoculars and telescopes roughly similar in size and shape.  Both Andromeda and the Milky Way Galaxy we inhabit are huge conglomerations of stars. We’re about 100,000 light years in diameter – Andromeda is about 150,000 light years in diameter. The Milky Way contains perhaps 100 billion stars – the Andromeda Galaxy maybe 300 billion.  (Don’t quibble over the numbers – even the best estimates are just estimates. )

And yes, in a few billion years we will probably “collide” with the Andromeda Galaxy, for we are hurtling towards one another. Such galaxy collisions are not that unusual  and probably aren’t as violent as the word “collision” makes them sound – but they do, in slow motion, bring about radical changes.

But all that is for the professional astronomers to concern themselves with – for us, there’s the simple beauty and awe of knowing that with our naked eye – or modest binoculars – we can let the ancient photons from hundreds of billions of stars ping our brains after a journey of millions of years.

And now the truth about Algol and companions

Have you done the Algol test yet? Looked at Algol, Mirfak, and Almach and tried to decide which is brightest? If so, you can check your answer by continuing to read. If not, I suggest you first do that exercise, then come back to this.

Chances are that when you look at Algol, it will be at its brightest – but how can you tell? Well, as we mentioned, you can compare it to Mirfak – but there’s an even closer match with another nearby bright star – Almach.  That’s the third star in Andromeda’s Couch  – the one neareast Algol.

Mirfak is the brightest of the three at magnitude 1.8.

Almach is magnitude 2.1 – the exact brightness of Algol when Algol is at its brightest – which is most of the time. OK – for the hair splitters, Almach is a tad dimmer, but the difference is far too little to be able to tell with your eye.

Here’s a chart showing the magnitude of the stars near Algol that you can use to compare it to and see if it is going through an eclipse.  People who look at variable stars use charts like this, but with one important exception – the numbers are given like they were whole numbers so you will not confuse a decimal point with another star. Thus, a star like Mirfak, of magnitude 1.8, would have the number “18” next to it. I broke a convention here because there are just a few bright stars on the chart, so I didn’t worry about the possible confusion of a decimal point being another star.

So If Algol and Almach are the same, no eclipse is going on at the moment.  If Algol appears dimmer than Almach, then an eclipse is in progress. If it’s as dim or dimmer than either of the companions of Mirfak in the Bow, then you can be pretty sure you’ve caught Algol at or near  its darkest. In two hours – or less – it will start to brighten and will return to full brightness fairly quickly.

Catching Almach at its dimmest is fun, but not as easy as it may seem. Why? Because although  an eclipse happens every few days, it may happen during the daylight hours, or in the early morning, or some other time when it’s inconvenient. And, of course, you need clear skies.  So when I want to observe an Algol eclipse, I go to a handy predicting tool on the Web that you can find here.

I then note the dates and times and pick out only those dates when the times are convenient to me – that is, happening during my early evening observing sessions. Then, given the  iffiness of the weather, I usually find that there are only one or two times a month when I’ll get a good look at an eclipse of Algol.

If I do this for October I find that out of 11 Algol minima, just three hit at the right time for me. Those dates and times are:

• 10/01/2009  9:09 pm EDT
• 10/21/2009  10:50 pm EDT
• 10/24/2009  07:39 pm EDT

Of course the dates and time may be different for you, depending on where you live, and none of us can escape the whims of the weather! So here’s hoping for clear skies for you so you can find a winking demon, follow the actions of Jupiter, and capture in your own eye the photos from a few hundred billion stars in the Andromeda Galaxy!

Jupiter’s back-and-forth wanderings

On October 1, 2009 a nearly full moon joins Jupiter, Uranus, and Neptune in the southeast as shown here about an hour after sunset. (Jupiter is made large to indicate its relative brightness - ut it will look like a very bright star - not a small moon!) This is how the sky appears from latitude 42 degrees north and longitude 71 degrees west. Chart from Starry Nights Pro software. Click for larger image.

The idea here is simple – connect what we can see in the sky this month with what’s actually going on. We’ll do this by watching Jupiter, the easiest object to find right now since it is the brightest “star” fairly high in the southeast shortly after sunset.

With just a few quick checks with binoculars we should be able to track the movement of Jupiter in relation to a bright, nearby star. You should start this project on or before October 1, 2009 if at all possible and plan to observe two or more nights between your start time and October 13. Then observe again in about a week and again near the end of the month.Your first couple of checks should show Jupiter in “retrograde” moving westward among the background stars. Your next two checks should show Juputer has resumed it’s normal eastward movement.

Use the following chart as both your guide and your log. That is, click on it to get a version you can print, take out under the stars, and record your observations on with a pencil.

Click for larger version, suitable for printing.

So why does Jupiter appear to first go one way, then the other? Afterall, it isn’t really doing that, is it? Like the other planets – and us – it’s simply continuing a steady, eastward journey around the Sun. But so are we – and we are moving much faster because we’re much closer to the Sun. So what you are seeing is partly the movement of Jupiter – but also the apparent change in its position caused by our rapidly changing position.

I made the following animation from Solar System Live charts. It shows how Jupiter’s position changes slowly in relation to Earth and the other planets, particularly Neptune. The animation starts with September 1, 2009  and moves a month at a time for six months. The arrow shows our changing view of Jupiter with relation to Neptune, a much more distant – and even more slowly moving, planet. Notice that in late December Jupiter makes another close approach to Neptune – the third this year – which will make especially easy at that time to find this distant and faint planet. Right now you can use the chart above to track it down – it would be just visible in binoculars on a moonless night.

So let’s review the movements we’re dealing with here.

1. The daily rotation of the Earth causes Jupiter to appear to rise inthe east and move westward as the night progresses.

2. The revolution of the Eartha round the sun at a much higher speed than Jupiter makes it so that for some time the huge planet appears to be moving westward in relation to background stars and the more distant planet Jupiter. That apparent westward motion comes to a stop October 13, 2009.

3. Jupiter’s own motion is more apparent after October 13, as it appears to move eastward against the background stars. This general motion will carry it about 30 degrees eastward – very close to where Uranus can be found now – in about a year. It takes Jupiter almost 12 of our years to make a complete circuit of the sky.