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    My Journey through the Astronomical Year

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

Look North in March 2014 – Oops, there’s a big hole in the sky!

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

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

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

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

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

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

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

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

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

Click image for larger view.
There was a logic to this giraffe-like telescope.
At the time a telescope’s lens could not bring the different colors of light to a single focus, so bright objects were always fringed with color and nothing was in really sharp focus. This negative effect, however, could be lessened by making the telescope’s focal length longer – so to get a really good telescope you had to go to these ridiculous extremes – which, of course, made it a nearly impossible telescope to use in any practical way.
Impressive to look at – difficult to aim and look through.
Fortunately the achromatic lens – combining two different types of glass – was invented and this reduced the problem considerably even in a relatively short telescope. We still use such achromatic lenses today ins mall refractor, though if you want to get a really sharp, color-free image you pay considerably more money for an apochromatic lens. Or, you listen to Newton who figured way back int he 1600s that the way around this was to design a telescope that used a mirror to collect the light rather than a lens. Trouble was, it took a long time to learn how to make mirrors that didn’t tarnish quickly when exposed to the night air. Nothings easy!
Now – about or “hole” in the northern sky. Get to a place where light pollution is at a minimum and it will fill with stars – relatively faint, but they are there. Just scan around with binoculars and you’ll find some even through the typical light pollution most people today are forced to endure. 

Look East: March 2014 Roars in like a sickle and triangle! (Huh?)

Sure, I’d like to tell you March roars in like a lion – but honestly it’s easier to point to the sickle and the triangle and the “Little King” we call Regulus, this last being the new guidepost star for March. But there is a lion there, too. Let’s look at the sickle and triangle first, though, because they’re two very easy asterisms you’ll see in the east about an hour or so after sunset. The Big Dipper off to the northeast gives you an idea of size for comparison – and the same pointer stars you use inthe DIpper to point to the north star – they can be used to point inthe opposite direction where they come very close to Regulus, about 45 degrees away.

This is the eastern sky as it will appear about an hour after sunset from mid-northern latitudes. Click image for larger view. Prepared from Starry Nights Pro screen shot.

This is the eastern sky as it will appear about an hour after sunset from mid-northern latitudes. Click image for larger view. Prepared from Starry Nights Pro screen shot.

Click for printer friendly version of the above chart.

OK – so can you make this into a lion? I find it fairly easy if I consider the sickle his head and mane – and I consider the triangle his rear haunches. I leave the rest to my imagination and don’t really attempt to connect the dots.

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

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

Regulus, our new bright guidepost star for this month, means “little king,” or “prince,” in Latin. That fits right in with the lion‘s reputation as King of the Beasts. And what a lovely image to have a prince leading a lion onto the night-time stage this month!

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

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

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

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

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

Vital stats for Regulus:

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

The buzz about the Beehive (M44) and Leo’s whiskers – a binocular treat!

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

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

Whiskers indeed! I like that. It’s a great way to remember where to look for M44, for if you can find the Sickle – the huge head and mane of Leo – then all you have to think is “now where would his whiskers be?” Scan 2-3 binocular fields in that direction – westward – and you should soon stumble upon M44, the Beehive. Here is a chart you can use to find it. Do wait  until about two hours after sunset when it is really dark and M44 is well up in the sky.

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

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

M44 also is known as “the Beehive,” and Praesepe, which is Latin for manger. And if you have dark skies, away from light pollution, you will see this as a small, wispy cloud, perhaps suggestive of Leo’s whiskers. It is, in fact, a beautiful star cluster as binoculars or a small telescope will reveal. Galileo first discovered its true nature, and in this hazy patch counted more than 40 stars. You should see about that many with your binoculars. This is one of the nearest star clusters to us, and although there is still debate over its exact distance, it is around 580 light years. That compares with about 400 light years for the Pleiades. The two clusters are pretty close to the same size, but M44 is considered much older. M45 – the Pleiades – is estimated to be 78 million years old, while M44 is thought to be about 660 million years old. As star ages go, they’re both quite young. But open clusters, such as these, do not last too long – the members stars tend to get drawn off by close encounters with other stars as the whole clusters moves about our Milky Way galaxy.

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

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

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

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

Look East: March 2013 Roars in like a sickle and triangle! (Huh?)

Sure, I’d like to tell you March roars in like a lion – but honestly it’s easier to point to the sickle and the triangle and the “Little King” we call Regulus, this last being the new guidepost star for March. But there is a lion there, too. Let’s look at the sickle and triangle first, though, because they’re two very easy asterisms you’ll see in the east about an hour or so after sunset. The Big Dipper off to the northeast gives you an idea of size for comparison.

This is the eastern sky as it will appear about an hour after sunset from mid-northern latitudes. The circle represents a typical field of view for low power binoculars. While you should see the brightest stars easily, in twilight - or in typical light pollution - you'll find that binoculars will show some of the fainter stars nearby and help you be sure you have identified the correct bright star.  The Mars position is for the 15th, but it will change a little each night.  Click image for larger view. Prepared from Starry Nights Pro screen shot.

This is the eastern sky as it will appear about an hour after sunset from mid-northern latitudes. Click image for larger view. Prepared from Starry Nights Pro screen shot.

Click for printer friendly version of the above chart.

OK – so can you make this into a lion? I find it fairly easy if I consider the sickle his head and mane – and I consider the triangle his rear haunches. I leave the rest to my imagination and don’t really attempt to connect the dots.

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

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

Regulus, our new bright guidepost star for this month, means “little king,” or “prince,” in Latin. That fits right in with the lion‘s reputation as King of the Beasts. And what a lovely image to have a prince leading a lion onto the night-time stage this month!

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

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

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

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

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

Vital stats for Regulus:

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

The buzz about the Beehive (M44) and Leo’s whiskers – a binocular treat!

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

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

Whiskers indeed! I like that. It’s a great way to remember where to look for M44, for if you can find the Sickle – the huge head and mane of Leo – then all you have to think is “now where would his whiskers be?” Scan 2-3 binocular fields in that direction – westward – and you should soon stumble upon M44, the Beehive. Here is a chart you can use to find it. Do wait  until about two hours after sunset when it is really dark and M44 is well up in the sky.

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

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

M44 also is known as “the Beehive,” and Praesepe, which is Latin for manger. And if you have dark skies, away from light pollution, you will see this as a small, wispy cloud, perhaps suggestive of Leo’s whiskers. It is, in fact, a beautiful star cluster as binoculars or a small telescope will reveal. Galileo first discovered its true nature, and in this hazy patch counted more than 40 stars. You should see about that many with your binoculars. This is one of the nearest star clusters to us, and although there is still debate over its exact distance, it is around 580 light years. That compares with about 400 light years for the Pleiades. The two clusters are pretty close to the same size, but M44 is considered much older. M45 – the Pleiades – is estimated to be 78 million years old, while M44 is thought to be about 660 million years old. As star ages go, they’re both quite young. But open clusters, such as these, do not last too long – the members stars tend to get drawn off by close encounters with other stars as the whole clusters moves about our Milky Way galaxy.

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

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

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

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

Look North in March 2013 – Oops, there’s a big hole in the sky!

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

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

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

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

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

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

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

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

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

Click image for larger view.
There was a logic to this giraffe-like telescope.
At the time a telescope’s lens could not bring the different colors of light to a single focus, so bright objects were always fringed with color and nothing was in really sharp focus. This negative effect, however, could be lessened by making the telescope’s focal length longer – so to get a really good telescope you had to go to these ridiculous extremes – which, of course, made it a nearly impossible telescope to use in any practical way.
Impressive to look at – difficult to aim and look through.
Fortunately the achromatic lens – combining two different types of glass – was invented and this reduced the problem considerably even in a relatively short telescope. We still use such achromatic lenses today ins mall refractor, though if you want to get a really sharp, color-free image you pay considerably more money for an apochromatic lens. Or, you listen to Newton who figured way back int he 1600s that the way around this was to design a telescope that used a mirror to collect the light rather than a lens. Trouble was, it took a long time to learn how to make mirrors that didn’t tarnish quickly when exposed to the night air. Nothings easy!
Now – about or “hole” in the northern sky. Get to a place where light pollution is at a minimum and it will fill with stars – relatively faint, but they are there. Just scan around with binoculars and you’ll find some even through the typical light pollution most people today are forced to endure. 

Update- March 5 – Outlook brightens for PanSTARRS!Events – March 2013: Get set for a real nice – BINOCULAR – Comet and more

NASA guide to PanSTARRS position and tail direction on different dates this month. This is NOT a prediction of tail length or comet brightness. It is likely tobe much shrter and fainter - but comets are full of surprises and so this still has the potential to be really nice.

NASA guide to PanSTARRS position and tail direction on different dates this month. This is NOT a prediction of tail length or comet brightness. It is likely to be much shorter and fainter – but comets are full of surprises and so this still has the potential to be really nice. (Click image for larger version.)

The latest indicators are that Comet PanSTARRS will put on a better show than anticipated just a week ago – as noted, comets are just not that predictable! – here’s a recent news item:

Observers in the Southern Hemisphere have been watching Comet PanSTARRS for weeks, but the Northern Hemisphere is due to get its first looks at one of the year’s most eagerly anticipated sky extravaganzas this week. And there’s good news for northerners: The up-and-down expectations for the cometary show are trending upward again.

March Observing Highlights  –

Comet PANSTARRS and its distant kin, the Zodiacal Light

First, let me stress Comet PanSTARRS is not likely to be nearly as bright as originally predicted – but it still should be a nice comet, especially when viewed with binoculars.  And remember – we have another due in November/December that should be much better. However, with comets we can only make educated guesses – they can – and have – surprised the experts over the years, sometimes under performing, sometimes over performing.

I’m linking this comet with the Zodiacal Light because both might be seen at their best on March 12 after sunset in the west. What’s more,  they are  both essentially dust reflecting sunlight,  presenting a related observing challenge, though they are radically different in size. March 12 may be the earliest time for a good look at Comet PanSTARRS in the early twilight – and it will be the last night in early March for the  Zodiacal Light which can be seen about 80 minutes after sunset for the first 12 days of March – after that the Moon will tend to wash out the Zodiacal Light until the last couple days of the month.

Quick Observing Guide:

  • to observe both comet and Zodiacal Light  at their best, hope for clear skies on March 12 – and some special comet luck 
  • to observe the Zodiacal Light  alone go out any evening during the first 12 days of March 2013 and look for it about 80 minutes after sunset.
  • to observe Comet PanSTARRS it may be visible – especially from low northern latitudes such as the southern US, as early as March 7 or 8th, but the week beginning March 12 will probably give the best opportunity for observers in mid-northern latitudes.

A comet is a “dirty snowball” that “melts” when it gets near the sun, giving off what can be a spectacular trail (tail) of tiny dust particles that reflect sunlight. When we think of a comet we are usually thinking of seeing one with such a tail.  And the Zodiacal Light? It’s tons of inter-planetary dust, much of it having accumulated over the years from many comets that eventually disintegrated as they made several trips around the Sun. And while your best views of Comet PanSTARRS will be when it’s near the Sun – but getting dark – your best view of the Zodiacal Light will be just as full darkness is arriving – about 80 minutes after local sunset.

The Zodiacal Light will be in a fixed position night after night – a huge, but very faint, light cone reaching from the western horizon and slanting up in the general direction of the Pleiades star cluster in Taurus  – Comet PanSTARRS will change position slightly each night, drawing away from the Sun. The Zodiacal Light is most certainly a naked eye phenomenon requiring a good view to the west and  skies that are largely free of light pollution in that direction.

The same basic requirements fit Comet PanSTARRS – you need a good view to the west with an unobstructed horizon, at least for the early – and probably best – views. While it may be visible to the naked eye, the best guess is this will be bets seen in binoculars. So by all means, break out the binoculars! You don’t need any thing special – ordinary, low-power ones will do, though if you have large astronomical binoculars, all the better.  And while you will be searching for the comet in the early twilight, do be careful. Wait until about 15 minutes after sunset before scanning the western horizon for it. At all cost, avoid looking with your binoculars at the sun, as that will seriously damage your eyes.

Yes, you are likely to hear that PANSTARRS is visible to the naked eye. Don’t get too excited, though, it’s visibility is a lot like that regular March visitor, the  Zodiacal Light – the numbers in reality don’t really add up. Thus the binoculars are highly recommended – even if its brighter than expected.

Great video guide to the comet from NASA

I read in Sky and Telescope this month that the Zodiacal Light is actually the second brightest “thing” in the Solar system.  Wow! Never prove that from my experience. I  have always found it elusive. I count myself lucky if I can see it at all!  But, of course, Sky and Telescope is right.  Here again there’s an important lesson relating to both the Zodiacal Light and a comet – the brightness they’re talking about is for a point object, but in our view of it, this light is spread out.

So when you hear the Zodiacal Light is beaten only by the Sun in brightness, you have to understand that this is determined by pretending all the light reflected from it was concentrated in a single spot – and it isn’t. It is spread out over a huge area of sky – widest near the horizon and getting narrower as it rises towards the Pleiades. For me it looks much like the Milky Way, only a bit fainter.

The same thing is true of a comet – but to a much lesser degree. That is, Comet PanSTARRS is fairly likely to reach magnitude 2 and if it does, well that’s as bright as the North Star, or most of the stars in the Big Dipper. But – and here’s the catch – that light will be spread out with much of it concentrated in the fuzzy head, but  some also appearing in the tail.

What’s more, as the comet draws away from the Sun it will almost certainly get fainter – and therein lies the crucial problem of seeing a comet at its best. What we are dealing with is a constantly changing set of variables. Generally speaking, the closer a comet is to the Sun, the brighter it is.  However, the closer it is to the Sun, the more it is competing with the lingering sun light. As the twilight deepens, the comet should stand out more – BUT, as the twilight deepens the comet is also getting lower in the sky and that means you’re looking at it through more atmosphere and that makes it appear dimmer.

So the joy – and frustration – of comet hunting is that how the comet looks to you will depend on your local weather, of course, but also exactly when you see it – how bright it is, how high it is, and how dark the sky is around it. That’s what makes viewing – and photographing – comets both fun and challenging.

So what’s the best bet for Comet PanSTARRS – for those in mid-northern latitude somewhere between March 7 and 20 probably about halfway in between. I plan to watch the weather closely from March 10th to 17th and take advantage of any clear evening to look for it. The farther south you are, the sooner it should appear at its best for you – the farther north,  the later in the month it will be at its best.

But remember – on a  clear night early in the month that you go comet hunting – hang around even if the comet is too low to see well – the Zodiacal Light should be best about 80 minutes after sunset when there is no – or little – interference from the Moon. (That means from March 1 to about March 12, 3013.)  If you see the Zodiacal Light – how well you see it depends largely on timing, local weather conditions, and the lack of light pollution.  In other words, it is not quite to finicky as the comet, but still a challenge.

Jupiter – King of the Winter Hexagon!

Wow! What a view to the south!

As the sky darkens on these March evening, don't hesitate to look due south for a wonderful view of Jupiter dominating the Winter Hexagon - thata rea of sky with more birght stars in it than any other! Click the image for a larger version. (Prepared from Starry Nights Pro screen shot.)

As the sky darkens on these March evening, don’t hesitate to look due south for a wonderful view of Jupiter dominating the Winter Hexagon – that area of sky with more bright stars in it than any other! Click the image for a larger version suitable for printing. (Prepared from Starry Nights Pro screen shot.)

The Winter Hexagon is one of my favorite asterisms encompassing a very rich area of sky contains eight very bright stars and that most recognizable of constellations, Orion.  But bright as these stars are, Jupiter will dominate them, outshining even Sirius, the brightest star for norther hemisphere observers. Take a look in that direction about an hour after sunset – in fact, you can’t hope but notice this brilliant area as you scan in the darkening even sky for the Zodiacal Light which shine faintly in a widening cone reaching from near the Pleiades to the western horizon.

And what a fabulous binocular sight!

Use your binoculars to:

  • Look for the fuzzy area in Orion’s sword  which hangs below his belt – the Great Orion Nebulae.
  • Look for the Hyades – the fabulous star cluster that makes up the “V” of Taurus and is just 150 light years away.
  • Look for the Pleiades – my favorite binocular target, a cluster of brilliant gem stone roughly 400 light years away.
  • And, of course, if you can hold them steady enough – brace against a pole, or the corner of a house – try to pick up one or more of the four bright moons of Jupiter.
The "V" of Taurus marks the Hyades cluster and the Pleiades are bit to the right as seen when looking south about 90 minutes after sunset this month.  Watch carefully over the course of the month and you will see Jupiter slowly change position moving towards Aldebaran, the bright star that marks the bull's eye. (Click for larger version. Prepared from Starry Nights Pro screen shot.)

The “V” of Taurus marks the Hyades cluster and the Pleiades are a bit to the right as seen when looking south about 90 minutes after sunset this month. Watch carefully over the course of the month and you will see Jupiter slowly change position moving towards Aldebaran, the bright star that marks the bull’s eye. (Click for larger version. Prepared from Starry Nights Pro screen shot.)

Oh – and I should add that Jupiter will have a real close call with a “young” crescent Moon on March 17, 2013. Exactly how close will depend on where you are, but for me on the East Coast of the US, the Moon will pass within two degrees of the bright planet and add to the fun of binocular observing on that night. They both will fit easily into the same binocular field of view!

Saturn now dominates the morning sky

Think of it as “coming attractions” if you’re not a morning person. Saturn crosses over into our late evening sky and by next month it will be quite easy t see at a reasonable hour.  For March 2013, however, it is primarily the dominant planet in the morning sky.

In fact, this is a rare month for planets – well, I should say planets are rare this month. Jupiter and Saturn are, for all practical purposes, the whole show – the other major planets being too near the Sun for easy viewing.

Our chart shows Saturn at  mid-month and midnight due southeast and about 23 degrees above the horizon. Spica – which is about half a magnitude dimmer than Saturn, will be about 18 degrees away. Be sure to look for the color difference. Saturn should appear creamy – maybe a tad yellow, while Spica is an icy blue.

Saturn and Spica at midnight in March 2013. (Prepared from Starry Nights Pro screen shot. Click image for larger version.)

Saturn and Spica at midnight in March 2013. (Prepared from Starry Nights Pro screen shot. Click image for larger version.)

The “March” of the Planets – they’re just Wild in the West in March 2012 – what you’ll see and why!

March starts off with a double-barreled planetary bang as Venus and Jupiter  meet and dance briefly, while just below them Mercury puts in its best appearance of the year zipping up for an easy look, then zipping back down.

First we’ll describe what you can see in a few simple charts, then we’ll delve into why you see it on the premise that the actual sight is much more exciting if you know what’s really going on back stage!  ( We also have a neat appearance by Mars in the eastern sky and Saturn in the morning sky, but more on that later. Oh – and while Mercury favors northern hemisphere observers this month, those in the south do see a good Jupiter/Venus show.)

What you’ ll see – March 1 -15

Go out a few minutes before sunset to a point where you have an unobstructed western horizon. Bring binoculars if you like – even a small telescope, though the naked eye gives a terrific view of this show. First, enjoy the sunset – get a sense of the Earth turning beneath your feet, and where the Sun is as it sets – though don’t look directly at it and certainly do NOT point telescope or binoculars there.  Wait 15-30 minutes and here’s what you should see in the twilight.

March gets going with a bang with this great planetary lineup in the western sky - the highlight of which is fleeting and elusive Mercury. Like all the star charts in this post, this was prepared from Starry Nights Pro screenshot. Click any star chart image for a larger view.

Yes, that’s my fist in the foreground. But you can use yours to help you find Mercury, the faintest of these three bright planets. Mercury will be about 10 degrees above the horizon, half an hour after sunset.  Hold your fist at arm’s length and you will cover about 10 degrees. (Yes, smaller people – or larger – have different size fists, but the proportions of arm length to fist size stay the same so this generally works.)  If you see this planetary line up, here are some things to notice.

First, look at the relative brightness of the three planets:

  • Venus is the brightest of the three by far. It glows at magnitude -4.3. Only the Moon and Sun are brighter.
  • Jupiter is next in brightness at -2.2 – brighter than any star gets.
  • Mercury is near its brightest at -.9 – but that makes it dimmer than the brightest star, now high in the south, Sirius – it’s about half a magnitude brighter.  And the fact that Mercury is so low and in bright twilight will make it more difficult to see. Binoculars will help find it, but it should be quite easily seen with the naked eye, especially when you know where to look.

Second. use your fist held at arms length (see chart) to note how high Mercury is above the horizon. This will change rapidly over the next 10 days.

Third, use your fist to estimate the distance between Jupiter and Venus. (One fist is 10 degrees.) This too will change rapidly over the next two weeks as Jupiter “falls” towards Venus and Venus  appears to quickly climb towards Jupiter.

Here are some charts at five day intervals to show the changes you can expect to see.

March 5, 2012

March 10, 2012

March 15, 2012

 So why do the planets appear where and when they do and why does Mercury change so rapidly in both position and brightness. Hop in your spaceship and zoom to a point well over the Sun so you can look down on our Solar System and watch the planets revolve.  That will give you the answer.

The two planets closer to the Sun than us – Venus and Mercury – revolve the fastest and have the shortest orbits.  They also pass between us and the Sun and thus go through phases like our Moon because we only see part of the sunlit portion of the planet as this happens. The outer planets, including Mars, Jupiter , and Saturn (all visible in our skies in March) don’t go through such phases and they change position more slowly – especially Jupiter and Saturn.

So let’s start with an overview showing where we and the other planets are on March 1, 2012. (All of these views are taken from the Orrery at  “Solar System Live” – a web site I heartily recommend you visit often and play with by changing the dates, etc., as encouraged at that site.)

March 1, 2012 – the entire Solar System

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In this first view you need to imagine yourself on Earth. The Sun has just set, but you can see that when you look in the general direction of the Sun (west) you will see Mercury very close to it, Venus a bit farther away, and Jupiter farther away still.  If you turn around and look East you will see Mars near the Eastern horizon. Saturn is to the east as well, but will not be seen until near midnight and is really a morning sky object.

If you could look at the three bright planets in the Western sky with a small telescope, they would look something like the following picture.

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To see the phases of Venus and Mercury in a small telescope it is best to catch them in twilight – start about 10 minutes after sunset -again, be careful not to look at the Sun with your telescope as your eyes would be severely damaged. Wait until the Sun is well below the horizon.  Venus gets so bright once it is fully dark that it tends to dazzle and dance and it is more difficult to see the phases then.  Mercury, on the other hand, is seldom high enough to get a good look because you are looking through so much atmosphere – but this is the best chance to see it in 2012. The relative sizes you see here are roughly the way they would appear in a telescope – they don’t represent the actual size difference of the planets because Jupiter – the largest by far – is much farther from us than either Venus or Mercury and so appears smaller than it really is.

March 5, 2012 – dance of the inner planets

In the following sequence you will see the Orrery view of Earth and the inner planets, as well as a view of what we see in the sky on each date  and how the phases of Mercury are changing. These changes in phase should make clear why the planet appears dimmer with each day after  March 5. On March 15 it will be quite difficult to see, as it will not only be close to the horizon, but it will have fallen in brightness almost two full magnitudes – that’s roughly the same difference in brightness you see between Jupiter and Venus – quite a change!

Western sky planets March 5, 2012 with inset showing how Mercury would appear in a small telescope.

Notice how Mercury is getting between us and the Sun - soon it will be lost in the Sun's glare.

Mercury is now (March 15) quite low, quite faint, and very difficult to see - and no wonder - just a slither of its sunlit face is visible to us as it comes near to passing between us and the Sun.

Mars and Saturn

Mars is an easy shot, visible in the east right after sunset, though it will be easier to see if you wait an hour or two. Use the chart in the “Look East” post here.  Mars gets close to us every two years, but not all “close” approaches are the same. Mars has an eliptical orbit and sometimes we hit it – as we are in 2012 – when it is closest to us, yet about as far as it gets from the Sun. That means it’s around 65 million miles form us this month. In some years it can be almosy half that distance from us, so while amateur astronomers will train their telescopes on it this month, it will appear relatively small.

Saturn is a wonderful sight in a small telescope and you can easily find it in the morning sky with the naked eye. Here’s a chart for a couple hours before sunrise at mid-month. Note that it is pretty close to one of our bright, guidepost stars, Spica, and they are roughly equal in brightness.

The early morning sky to the southwest is rich in bright stars and planets. Prepared from screenshot of Starry Nights Pro software. Click image for larger version.

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

If you studied the “Look East” post this month you met  Regulus, Mars, the Sickle and Triangle of Leo in the early evening sky. Now as Sunrise approaches they are nearing the Western horizon.  Saturn and Spica make a nice pair in the southwest that are hard to miss, with bright Arcturus above them and the brilliant, reddish guidepost star, Antares about due south.

Look North in March 2012 – Oops, there’s a big hole in the sky!

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

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

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

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

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

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

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

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

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

Click image for larger view.
There was a logic to this giraffe-like telescope.
At the time a telescope’s lens could not bring the different colors of light to a single focus, so bright objects were always fringed with color and nothing was in really sharp focus. This negative effect, however, could be lessened by making the telescope’s focal length longer – so to get a really good telescope you had to go to these ridiculous extremes – which, of course, made it a nearly impossible telescope to use in any practical way.
Impressive to look at – difficult to aim and look through.
Fortunately the achromatic lens – combining two different types of glass – was invented and this reduced the problem considerably even in a relatively short telescope. We still use such achromatic lenses today ins mall refractor, though if you want to get a really sharp, color-free image you pay considerably more money for an apochromatic lens. Or, you listen to Newton who figured way back int he 1600s that the way around this was to design a telescope that used a mirror to collect the light rather than a lens. Trouble was, it took a long time to learn how to make mirrors that didn’t tarnish quickly when exposed to the night air. Nothings easy!
Now – about or “hole” in the northern sky. Get to a place where light pollution is at a minimum and it will fill with stars – relatively faint, but they are there. Just scan around with binoculars and you’ll find some even through the typical light pollution most people today are forced to endure. 

Building MESSENGER – the Model

NASA provides a neat little model you can make of the MESSENGER spacecraft by simply printing out the directions and doing a little cutting and folding. You can download it here. And if you have the energy and time, you can build a more sophisticated version by downloading this.

If all goes well, MESSENGER will become the first spacecraft ever to go in orbit about the planet Mercury. It will do so on March 17, 2011.  You can read all about MESSENGER – and how to see Mercury yourself  in March of 2011 –  by going to our March “Events” post.

Here are step-by-step photos of building the first – and simpler – of the two  MESSENGER models.  We’ve added a simple way to effectively display your work.

Tools:

  • scissors
  • paper glue (we used rubber cement)
  • model knife (optional)

Materials:

  • 4 sheets of paper – we used  24lb
  • a couple coffee storrers,  pipe cleaners, or something similar (most straws are too big around)
  • short length of  black thread
  • small piece of clear tape
  • paper clip

Building time is about 30-40 minutes.)

Step-by-Step

1. Assuming you have printed out the sheets, cut out the spacecraft body. (Click on any image to view a larger version.)

2. Cut out the three white circles (indicated by arrows) on the spacecraft body. I found a model knife was best for this. (You can actually do this as the first step – but in any event do it before folding.)

3. Fold along white lines to make the box-like body.

4. Put fast-drying glue on the edges of the folds.

5. Finish spacecraft body and set aside to dry.  Cut out the gold spacecraft sunshade.

6. Fold and  glue sunshade together with color side out.

7. Cut out the strip labeled “bridge,” fold lengthwise, and glue together, color side out.  Set aside to dry.

8. Cut out solar panels.

9. Fold, but do not glue together until you have noted the position the boom (coffee stirrer) will be inserted, This is marked by dotted lines on the dark side of the solar panels.

10. Put glue onthe inside being careful to leave the area marked by the dotted lines free of glue. (A tad tricky, since the lines are on  he other side.)

11.Fold the bridge along the dotted lines and glue one side of it to the spacecraft body in rectangle outlined on it.

12. Put glue on the taps of the bridge, then glue the sunshade to it. Set aside to dry.

13. We found that it was difficult to simply stick the boom into the slots left for them in the solar panels, but these slots were easy to open with any sharp object,. We used a toothpick to do the job.

14. We mounted one solar panel tot he boom,t hen slid the boom through the wholes in the spacecraft body.  We did not glue the solar panels as they seemed to fit tightly enough.

15. Here’s the almost finished spacecraft before  folding the sunshade to give it an arched shape and adding the thread and paper-clip hook to display it. Note the solar panels and gold side of the sunshade are pointed in the same direction – which would be towards the Sun with the instruments aimed at Mercury.

16. Ooops – alomost forgot the boom. Didn’t have a straw, or stirrer as recommended, so we used a pipe cleaner, cut down to size. We also folded the sunshade into a gentle arch that looks more like the pictures of the craft.  However, we found it awkward to display  the spacecraft properly by just sitting it down on something.  So we added a piece of black thread to the top, center edge of the sunshade with clear tape. On the other end I tied a paperclip , bent into a hook to make an easy hanger.  Here’s the thread taped to the sunshade.

17. And here’s the finished model, dangling under the lamp over the dining room table – a fitting. space age centerpiece for March, 2011! Hey – it’s a space craft. It’s not supposed to sit on the table. it’s supposed to be out there flying.

Looking at this  little modest model gives me pause . I try to develop a sense – in myself and in my visitors to Driftway Observatory – of the incredible emptiness of space by having one person hold a soccer ball representing our Sun while another visitor holds a 2mm glass bead representing our Earth.  On this scale Mercury would be less than 1mm in diameter – barely visible even when in your hand.  But I ask the person with the bead to hold it at what they think is the correct distance from the Sun. Usually they guess this to be a foot or two away – sometimes boldly they move several feet away. But no one guesses the correct answer, which is about 75 feet away. Now think of that. A 2mm bead – Earth – out at 75 feet from our soccer ball Sun!   Another 2mm bead – Venus – would be placed at about 54 feet out from the Sun.  And then a third, tiny Mercury – at roughly 29 feet.

And now try to imagine how tiny the real MESSENGER  spacecraft – roughly the size of a table – would have to be made to fit into this scale model! Then close your eyes picture the MESSENGER entering this vast, empty interplanetary ocean  and traveling for seven years in that emptiness, then arriving at just the right spot and just the right time, to be placed in orbit.  This vital little craft with its complex instruments going all that distance – almost 5 billion miles in total at speeds that sometimes exceeded 140,000 miles an hour.  (To put that in perspective, the fastest rifle bullet goes about 2,700 miles an hour and our Apollo astronauts traveled about 25,000 miles an hour during part of their lunar journey.

And all around Messenger is just about nothing except for a hostile emptiness and the incredible heat of our Sun as it moves in close.  Awesome! Just plain awesome. Three cheers for little MESSENGER – and three cheers for us – a species that dares to challenge the hsotile vastness of space, and send it’s robot silicon  and ceramic envoys on a mission of exploration for new knowledge.

Events: March 2011 – a special month for messages from Mercury, and it’s about time!


Mercury: As Seen from Our Backyards – and from Orbit

We don’t get a good look at Mercury often – and neither does NASA. But that all changes – for us and for NASA – this month.

Why don’t we get a good look at Mercury? Because this smallest of planets is just too darned close to the Sun, so it seldom gets high above the horizon, and when it shows up at all, it’s usually in twilight. Actually, in any given year we always have several chances to see it as one month it peeks above the eastern horizon just before dawn, then a couple of months later it gives us another opportunity when it is just above the western horizon right after sunset. March will be the best – and most convenient – chance for us to see it this year. In fact, we have the unusual situation of Jupiter pointing the way!

And NASA?

NASA hasn’t been to Mercury for 37 years! (The only NASA spacecraft to visit Mercury was Mariner 10 in 1974 and 1975.) In these days of space probes and planet landers, that’s a real long time between visits. But this month the MESSENGER spacecraft – which swooped in for a close look at Mercury while passing it in 2008 and 2009, hopes to complete its mission by becoming the first spacecraft to go into orbit around Mercury. NASA hopes it will be sending images and scientific data from orbit for the next year. Orbit insertion – after a flight of nearly seven years and nearly five billion miles – comes in mid-March just as we’re getting our best chance to see the elusive planet with our naked eye.

More details on the NASA mission in a moment, including a neat little spacecraft model you can build, but first let’s look at what we can see with our naked eye or when aided by ordinary binoculars.

 

Finding Mercury: Timing is everything

Lots of sky watchers never see Mercury, but it’s actually quite easy to see. You just have to look in the right place at the right time. And this year in March brilliant Jupiter is going to make it extra easy because Mercury stages a Jupiter flyby in the middle of the month. (Though Mercury and Jupiter will appear close together no matter where on Earth you’re seeing them from, this is generally a Northern Hemisphere event. The farther south you go, the earlier they set, and for much of the Southern Hemisphere they are either too near the horizon or already set by the time the sun sets.)

So here is when and where to get a good look at Mercury:

  • Of course you first need an unobstructed western horizon and very clear skies.
  • The charts are for about 30 minutes after sunset as seen from mid-northern latitudes – but generally good for anywhere in the Northern Hemisphere.
  • Each chart has a line on it indicating 10 degrees above the horizon – 10 degrees is what is covered by your first when held at arm’s length.
  • If you can find Jupiter, the brightest “star” low in the west, then you should have no trouble finding Mercury, which will be significantly dimmer, but still bright.
  • Binoculars will help, and the charts show a typical binocular field of view with Jupiter centered. (Caution: Be sure to wait until about 10 minutes after sunset before pointing binoculars in that general direction. Seeing the Sun with binoculars will damage your eyes!)
  • Pick a date from the charts below, click on the chart for a larger version, and plan to observe starting about 20 minutes after sunset and looking due west.
  • You may spot Mercury before and after these dates – these are just the easiest times because of the proximity to Jupiter.

March 11, 2011

March 12, 2011

March 13, 2011

March 14, 2011

March 15, 2011

March 16, 2011

March 17, 2011

March 18, 2011

March 19, 2011

March 20, 2011

March 21, 2011

Since ancient times Mercury has been known as “fleeting” and for good reason – it just doesn’t stay in one place for long, so look fast, because it will soon be gone again. This makes perfect sense when you consider that Mercury is the closest planet to the Sun and thus has the shortest orbit. It’s 88-day orbit means it goes around the Sun nearly four times while we’re making one trip. It is traveling at more than 107,000 miles an hour, while we’re poking along at just 66,000 miles an hour.

This shows the positions of Mercury and Earth on March 11, 2011. (Prepared from Solar System Live Orrey available on Web.)

I think of Mercury as something of a jokester. Because it is so close to the Sun, it’s always going to be near the Sun in our sky. That means it’s frequently drowned out by the light of the Sun. Even when it’s shining quite brightly, it may be doing so in bright twilight and thus be difficult to see. For example, as it gets higher in our sky this month, it should be easier to see because we’re looking through less atmosphere, and, of course, it’s farther away from the Sun so the background sky is darker. But, as it gets higher it’s also moving to a position more between us and the Sun and thus from our perspective we see less and less of the lit portion until it eventually becomes a crescent – so it actually gets dimmer. It is brightest at the start of the month and is a still a brilliant -1.3 on March 11. To put that in perspective, Sirius, the brightest star in our sky, is -1.5. But when Mercury is that bright it also is relatively low and thus in more twilight. In just 10 days it drops almost a full magnitude, to -0.5 – but it’s higher, so I suspect it’s likely to seem almost as bright. By the end of the month, though, it is magnitude 1.7 and has dropped to about 7 degrees above the horizon 30 minutes after sunset. Given the right conditions, this will make a nice target in a small telescope because it will show as a tiny crescent – but it will be much harder to find because of the twilight and dimness of the planet.


 

Meanwhile, Back at NASA, MESSENGER Is on an Historical Mission

None of this matters much to the folks at NASA. Their biggest challenge comes on March 17, 2011. They have high hopes, of course, but this is a complex mission, and while it has already returned significant images and new information, orbiting Mercury is the goal. Here’s how NASA put it in a recent press release.

“Although we feel that the preparations to date – and those scheduled for the next month – have been well thought-out, that the decisions made to define the specific activities were sound, and that the level of review and rehearsal has been more than adequate, we recognize the extraordinary complexity and unique nature of this endeavor,” says APL’s Peter Bedini, MESSENGER’s project manager. “But at this point, four weeks out, we are well positioned for success. The spacecraft is healthy, continues to operate nominally, and is on course to be at the right place at the right time at 8:45 P.M. ET on the evening of March 17.”

Of course they’ve had to solve tons of problems all along the way, not the least of which was how to protect delicate scientific instruments from the incredible heat generated by being so close to the Sun. The Sun is up to 11 times brighter at Mercury than here on Earth, and Mercury’s surface temperatures can reach about 840 degrees Fahrenheit. So the key to keeping MESSENGER cool (around average room temperature), is to have it carry its own beach umbrella – a sun shade made of heat-resistant ceramic cloth.

I remain in awe that the scientists and engineers can pull off a mission of this complexity. MESSENGER was launched August 3, 2004. It has reached speeds in excess of 140,000 miles an hour. (The Space Shuttle pokes along at 18,000 miles an hour when in orbit, and the fastest military jet is far slower than a Shuttle.) The straight line distance between Earth and Mercury can be as little as 60 million miles – yet the MESSENGER odyssey has taken it around the Sun and past Earth in 2005, past Venus in 2006 for a close flyby and a second Venus flyby in 2007, followed by Mercury flybys in January and October of 2008 and another in September of 2009. These close approaches to the planets can cause the spacecraft to speed up or slow down – and, in fact, it is the slowing down that has been part of the reason for the recent flybys of Mercury. In the 2009 event the speed of the spacecraft was cut from 12,000 mph to 6,000 mph and that was a critical to putting it into position for going into orbit. (I found this animation of the entire mission a bit hard to follow – I had to pause it at several stages – but that is simply because the mission is indeed lengthy and complex.)

An image from a Mercury flyby in January 2008 showing portions of the planet never imaged before. (Click for a much larger version.)

MESSENGER will still need its on-board rocket motors for the final maneuvers and, in fact, will use most of its stored fuel for this last effort. Here’s how NASA describes its plans for the night of March 17:

At 8:45 p.m. EDT, MESSENGER — having pointed its largest thruster very close to the direction of travel — will fire that thruster for nearly 14 minutes, with other thrusters firing for an additional minute, slowing the spacecraft by 862 meters per second (1,929 miles per hour) and consuming 31% of the propellant that the spacecraft carried at launch. Less than 9.5% of the usable propellant at the start of the mission will remain after completing the orbit insertion maneuver, but the spacecraft will still have plenty of propellant for future orbit correction maneuvers.
The orbit insertion will place the spacecraft into an initial orbit about Mercury that has a 200 kilometer (124 mile) minimum altitude and a period of 12 hours. At the time of orbit insertion, MESSENGER will be 46.14 million kilometers (28.67 million miles) from the Sun and 155.06 million kilometers (96.35 million miles) from Earth.

There’s a wonderful animation of the orbit insertion here, but this is a large file, so you need patience for the full movie to download.

NASA artist conception of MESSENGER spacecraft. All the alphabet soup refers to different instrument packages.

MESSENGER is a far cry from the Buck Roger’s style space ships we used to see in the movies and comic books. It’s a boxy little craft with instrument packages stuck on here and there and two wing-like solar panels for battery power, plus the sun shield. All of this in a squat box measuring roughly the size of a desk – about four feet by four and a half feet, by six feet. The thermal shade is about four feet by eight feet and semi-cylindrical. It weighs in at about 2,300 pounds and more than half of that is fuel.

NASA provides a neat little model you can make of MESSENGER by simply printing out the directions and doing a little cutting and folding. You will find complete step-by-step photos with download links to the model here.

What can we learn?

As the mission began, NASA outlined its goals. Some of these have already been achieved to one degree or another in the Mercury flyby by MESSENGER. But all can benefit from more exploration.The flyby gave a quick look – and an opportunity to image most of the planet. But being on station for a year is much different than taking a snapshot. Still, here are the basic scientific objectives as NASA outlined them:

Mercury’s density implies that a metal-rich core occupies at least 60% of the planet’s mass, a figure twice as great as for Earth. MESSENGER will acquire compositional and mineralogical information to distinguish among the current theories for why Mercury is so dense.

Before the MESSENGER mission, only 45% of the surface of Mercury had been photographed by a spacecraft! Using its full suite of instruments, MESSENGER will investigate the geologic history of Mercury in great detail, including the portions of the planet never seen by Mariner 10.

Mercury has a global internal magnetic field, as does Earth, but Mars and Venus do not. By characterizing Mercury’s magnetic field, MESSENGER will help answer the question of why the inner planets differ in their magnetic histories.

Through a combination of measurements of Mercury’s gravity field and observations by the laser altimeter, MESSENGER will determine the size of Mercury’s core and verify that Mercury’s outer core is molten.

At Mercury’s poles, some crater interiors have permanently shadowed areas that contain highly reflective material at radar wavelengths. Could this material be ice, even though Mercury is the closest planet to the Sun? MESSENGER will find out.

MESSENGER will measure the composition of Mercury’s thin exosphere, providing insights into the processes that are responsible for its existence.

Undoubtedly, there will be surprises. In fact, there already have been. For example, in the flybys, what looks like ice was discovered on parts of the planet. Keeping in mind that typical temperatures on Mercury would make a pizza oven seem comfortably warm, that’s astounding. Here’s NASA’s take on the ice:

So how is it that the planet closest to the Sun has temperatures that possibly can sustain ice? Simply, Mercury’s axis of rotation is such that sections of the planet, the deep floors and walls of craters near its poles, are always shaded. In these frigid areas of Mercury, temperatures can dip to minus 350 degrees Fahrenheit. Radar pictures from Earth show material in the craters that resembles ice, but its identity is one of Mercury’s mysteries that NASA hopes to solve.

Now this is not a place I want to spend my next vacation! I mean 840 degrees in the Sun and -350 degrees in the shade! Sure helps put our seasons into perspective – and MESSENGER gives us a lot to ponder as we watch this beautiful little “evening star” climb up our western sky and pass mighty Jupiter this month. The ancients marveled at Mercury, their “messenger of the gods.” But the more we learn about it through our modern MESSENGER, the more awesome it becomes.


 

Spring Equinox and Zodiacal Light

Don’t forget the equinox – a great time to note where east and west really are on your horizon, for the sun rises and sets due east and due west that day and for all practical purposes a few days before and after the equinox.

This year the equinox arrives in the Northern Hemisphere at 7:21 EDT on March 20th.

Oh darn! Yes, that is “daylight time.” For most of the U.S. and Canada “daylight time” began at 2 am, March 13. I say “darn” because they keep making the Daylight Time period longer – starting it sooner and ending it later in the year – and that makes it difficult for little kids to get out and observe when it’s really dark – an hour and a half after sunset. Frequently, by the time it’s dark, it’s too late for them. And, of course, they can observe in the winter when it gets dark early, but frequently our winter nights are too cold for them. Makes it difficult to share the beauty of the night sky and the awe of the universe with our younger citizens!

Beauty — like the delicate glow that reaches up from the western horizon on a March evening and is known as the Zodiacal Light. I wrote more about it last month. However, March is the best time to see it, and you need an area as free of light pollution as you can get. We’re talking about something about as faint as the Milky Way, so your eyes must be dark adapted and you don’t want any competition from the Moon. For March, 2011, you could look the first few days of the month, or wait until the last two weeks of March or the first few days of April. You want to start looking about an hour and 20 minutes after local sunset.


 

The Moon and Other Planets This Month

  • New Moon, March 2
  • First quarter, March 12
  • Full Moon, March 19
  • Last quarter, March 26.

The crescent Moon makes a nice paring with Venus on the morning of March 1 and joins it once more on the 31st – sort of lunar bookends for those early morning star gazers. Also, it is near Jupiter on March 5th and 6th.

We bid farewell to Jupiter this month, which should be obvious if you checked out the maps showing it and Mercury earlier in this post. But as it sets in the west, Saturn is rising in the east, and it’s a special treat for the users of small telescopes, though they’ll have to stay up late for the best views. (When using a telescope it’s best to look at stars and planets when they’re high in the sky.) Don’t expect to see the rings in binoculars, however; they’re not powerful enough. But any small telescope will show them.

As the month begins Saturn rises about two hours after sunset, which means you’ll get a good look at it about a fist or so above the horizon in the southeast three hours after the Sun sets. By the end of the month it’s rising as the Sun sets – but, of course, on the other side of the sky. The full Moon gets fairly close to it on the 19th. The bright star in the same general vicinity is Spica, a guidepost star we’ll leave for another month.

Spica is about as close to first magnitude as you can get and very blue. Saturn will be at its brightest in March at about magnitude .4, so you should see it as brighter than Spica with a distinct yellow hue. (For more on star colors, how to see them, and what they tell us, see this post.)

Venus is still a lovely “morning star” and stays with us all month, though it rises only about two hours before the Sun, so it is best seen in twilight, low in the southeast. You can’t miss it though. Nothing outshines it except the Moon and the Sun.

Look North in March 2011 – Oops, there’s a big hole in the sky!

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

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

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

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

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

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

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

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

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

Click image for larger view.

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