Archive for the ‘Constellation’ Category

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The pilgrimage to Palomar, constellations by DSLR, and the Azusa fire

September 3, 2012

I have been fortunate to visit two of the great research observatories in California: Lick Observatory on Mount Hamilton, overlooking San Jose, which got me into all this in the first place; and Mount Wilson Observatory, where I’ve gotten to observe twice with the 60-inch telescope.

For a long time I have been meaning to get to the third major research observatory in California: Palomar. The building of the 200-inch (5-meter) telescope during the Great Depression was one of the first scientific “megaprojects”, something akin to the Apollo program or the search for the Higgs boson, and it caught the public interest in much the same way. After serious war-related delays, the great machine was finally dedicated in 1948, had its official first light in 1949, and started regular research observations in 1950–a program that continues to this day. The 200-inch telescope was absolutely the world’s largest telescope from 1948 to 1976, and effectively the world’s largest telescope until the first Keck telescope came online in 1993. The 6-meter Soviet BTA-6, which was completed in 1976, was more of a publicity stunt than a functional instrument and has not lived up to its potential, although I hear it is being overhauled so maybe that will finally change.

If you are remotely interested in the history of big telescopes in general and the history of the 200-inch in particular, I highly recommend The Perfect Machine, by Ronald Florence. If I started relating all the interesting anecdotes about the building of the telescope, we’d be here forever–it will be faster and more enjoyable to read the darn book.

Anyway, yesterday I was staring down the barrel of a 3-day weekend with no definite plans. I decided that it was finally time to go see the “big eye” at Palomar Mountain. London and I didn’t get on the road until early afternoon, so we got down there too late to visit the observatory yesterday. Instead, we went to nearby Palomar Mountain State Park for a phenomenal sunset and some early evening stargazing.

I had along a new toy: Vicki loaned me her Nikon D70 DSLR. She’s had it for three or four years, I’ve just never used it. It’s been on my to-do list, though, and Kevin’s results on Mount Baldy a couple of weeks ago gave me just the kick that I needed. I have been waiting not-s0-patiently for the full moon to pass so that I could try my hand at photographing constellations.

London in the meadow by Doane Pond, with the handle of the dipper hanging overhead.

After sunset London and I went down to Doane Pond, which sits in a nice little bowl with mountains on all sides. We went on a night hike around the pond, which resulted in us accidentally scaring several bullfrogs and them scaring us right back–few things are more alarming than an unsuspected animal making sudden noisy movement right by your feet in the dark. I also stopped at various places around the pond to photograph the sky, the pond, or the sky reflected in the pond.

I should preface all this by saying that I have no idea what I’m doing. This is my first time using a DSLR, I have no idea what about 95% of the controls do, and if you actually know photography you’d best put your beverage down now so you don’t spit it all over the keyboard. Nevertheless, I have read that one can get passable constellation photos with exposures of  30 seconds or less, and you are about  to see my first round of results.

I’ve been rereading Leslie Peltier’s Starlight Nights. I think of it, and Timothy Ferris’s Seeing in the Dark (the subject of this previous post), as “books about the why”. Loads of books will tell you how to stargaze, but very talk about the actual thoughts and emotions associated with the practice. If you want to know why to stargaze, go read Starlight Nights and Seeing in the Dark. Just be warned–if you’re not a stargazer now, you may be one by the time you’re done (also, if you’re not, I don’t know what you’re doing here, but welcome!).

Peltier writes with great warmth about his favorite stars, especially Vega, which was the first star he knew by name. I’d be hard pressed to name one favorite star, but I have a favorite constellation, and that is Cassiopeia. When I started getting into astronomy in the fall of 2007–almost five years ago, now–Cassiopeia was the first constellation I learned. All that autumn I turned my gaze northeast at dusk and found Cassiopeia first. She pointed me on westward to Cepheus and Draco and ultimately to Hercules and M13. To the south she led me to Pegasus, Aries, faint and frustrating Triangulum, and of course Andromeda and its magnificent galaxy. And following in Cassiopeia’s train as she climbed the eastern sky I found the Double Cluster and Perseus, the Pleiades, the Hyades, Auriga and its nice trio of Messier clusters, and the constellations of winter. Our romance has only deepened as I’ve gotten to know her better, for the velvety black folds of her dress are adorned with star clusters and nebulae almost beyond counting. Naturally, I pointed the camera in her direction first.

My first constellation photo–click through for the full-size, unlabeled version.

This is not a triumph of astrophotography. It’s grainy, it’s too bright, and the composition is not stellar (to, er, coin a phrase). But Cassiopeia is there, and I even see the Double Cluster just clearing the trees.

After paying my respects to Cassiopeia, I turned south, to Sagittarius and the summer Milky Way. Here’s the best of the lot, without labels.

And the same thing with constellations and deep sky objects labeled. Not every bright deep sky object is labeled, only those where I can see at least a smudge or a couple of bright pixels. Still, there are at least 19 DSOs visible in what was probably a 20- or 25-second exposure.

I am really looking forward to trying this under darker skies. It never got truly dark at Doane Pond, because the nearly-full waning gibbous moon rose well before the end of astronomical twilight. I think that without the moon it would have gotten very dark–maybe not stupid-dark like the remote places in the Mojave, but darker than Mount Baldy.

One more: the Big Dipper over Doane Pond, with a couple of its stars reflected in the pond. The pond was about as still as it could be, given the number of big splashes caused by alarmed bullfrogs (and, therefore, ultimately caused by me!).

Two things you shouldn’t mess with. To truly grok the immensitude of the telescope, check out the normal-size, full-width ladder going up one beam on the near side. The fork arms on either side have stairways inside for servicing the drive motors.

Today we went up to the top of the mountain and toured the observatory. Oddly enough, I don’t have a ton to say about this, beyond the obvious things. Which are (1) it’s awesome, and (2) if you live within striking distance, you should definitely go. Get there in time to get tickets for the guided tour–it’s waaaaay better than the self-guided tour, the docents are friendly and know a ton about the telescope and its history, and you’ll get to go up onto the catwalk inside the dome and get a much better view of the scope than you can from the little glassed-in visitor area on the dome floor. You really need to walk under and around the scope to get a sense of how immense it is, and you can’t do that except on the guided tour. I have been around some big scopes, including the 3-meter Shane reflector at the Lick Observatory, and the 200-inch makes all the others I’ve seen look like toys. Even knowing intellectually how big it is, I still walked in and thought, “OMG that’s big.” It’s inhumanly big.

The only downside to the whole trip is that as I was packing us up to leave, I momentarily set my observing notebook on top of the car–and then forgot to get it before we drove off. That’s a bummer. I have almost all of the observations backed up in my digital observing log (a huge Excel file), but the notebook had lots of sketches and there were probably a few object descriptions that I had not logged digitally. There’s a slim chance it will turn up, but I’m not holding my breath.

One final thing: there’s a wildfire burning in the Angeles National Forest above Azusa. It started just this afternoon. London and I saw it when we were coming home on I-15, as a fat pyrocumulus cloud squatting on the San Gabriels like a big evil god. At sunset I went to the top of the Claremont parking garage and watched it for a while. It must have hit a new fuel source around then because as I was watching it took about 10 minutes to go from this:

to this:

While I watched, I saw and heard several helicopters making runs to dump either water or fire-retardant foam. At that time, the fire had spread to more than 1000 acres and percent containment was zero. I’ve been up in the mountains lately and they’re bone dry, so this could be a bad one. My prayers are with the firefighters, and the people whose homes lie in the path of the fire.

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Mission 15: Ring of Fire

January 16, 2010

Mission Objectives: Bright Stars, Constellations

Equipment: Naked eye

Required Time: 2 minutes

Related Missions: Three Astronomical Treats for Naked Eyes, Binoculars, and Telescopes

Introduction: It’s a new mission for a new year. New stars are in the skies, and it’s the perfect time to start exploring the heavens–for the first time if you’re new to this, or exploring it again if you’re an old hand. This mission requires no prior knowledge, experience, or equipment; it’s just about getting out and getting acquainted with the night sky.

Instructions: Go outside after dark, face southeast, and find three stars in a straight, vertical line. These are the stars of Orion’s belt. They are flanked on either side by twin bright stars of roughly equal brightness but different color. On the left is Betelgeuse, an enormous red giant that appears yellow to the naked eye. On the right is Rigel, a blue-white supergiant.

Follow the line made by the belt stars down to even brighter Sirius. Sirius is the brightest star in Earthly skies, but it’s a not a giant or supergiant like Betelgeuse and Rigel. In fact, Sirius is a main-sequence star, a little less than twice the diameter of the sun, but about 26 times as bright. By comparison, Rigel is about 40,000 times as bright as the sun. But Rigel is 773 light years away, whereas Sirius is only 8.6 light years from us–the fifth closest stellar system to our own. Sirius, the Dog Star, is the chief star in the constellation Canis Major.

From Sirius, hang a right-angle left turn and head on to Procyon, “before the dog”, so named because it rises just a few minutes before Sirius from mid-northern latitudes. The small and otherwise dim constellation Canis Minor has little else to recommend it, and Procyon serves mainly as a celestial landmark.

Farther left still, and farther up in the sky, are the twins, Castor and Pollux, at the head of the constellation Gemini. If you have trouble keeping them straight, remember that “Castor is close to Capella, but Pollux is in proximity to Procyon”.

Speaking of Capella, it’s the very bright star directly toward the zenith from Castor and Pollux. It’s a brilliant gem in a ring of prominent stars that mark out the constellation Auriga, the Charioteer (this is not the big ring marked in red on the diagram above, but the much smaller blue-white ring on the upper left).

To the right of Capella is Aldebaran, the burning red eye of Taurus, the Bull. Aldebaran means “the follower”, because this star rises after the Pleiades, which it appears to chase from horizon to horizon (to trace that line, see the previous mission). Aldebaran is an orange giant, meaning that it has exhausted the hydrogen in its core and moved off the main sequence. Without the outward pressure of radiation from hydrogen fusion to prop it up, the core of the star is compacting under gravity and heating up. When it gets hot and dense enough to start fusing helium, Aldebaran will bloat into an immense red giant, like its neighbor, Betelgeuse.

And speaking of Betelgeuse, it lies in the middle of the great circle described by Rigel, Sirius, Procyon, Castor and Pollux, Capella, and Aldebaran. I call it the Ring of Fire–nowhere else in the northern sky is there an equal concentration of bright stars.

Below and to the left (east and north) of the Ring of Fire is Mars, which will be at opposition–opposite the sun, and at its closest approach to Earth–in a couple of weeks. The orbit of Mars is more elliptical than that of Earth, and this will not be one of the better oppositions, but it’s still the best look at the red planet that we’ll get for another two years.

What’s next? This mission was just a lightning run through the bright stars of winter. Their respective constellations are packed full of beautiful targets for binoculars and telescopes, and we’ll look at some of those in future missions. If you’re impatient to get started, download this month’s The Evening Sky Map, haul out your optics, and happy hunting!

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Mission 14: Three Astronomical Treats for Naked Eyes, Binoculars, and Telescopes

December 21, 2009

Mission Objectives: Bright Stars, Constellation, Open Cluster, Nebula

Equipment: Free star map, Naked eye, Binoculars, Telescope

Required Time: 10 minutes

Related Missions: Cassiopeia and the Double Cluster

Introduction: I’m in Oklahoma for the holidays. My best observation here so far didn’t require any optical aid at all. Remember last month when I was skunked in my quest to view the young crescent moon within 40 hours of new? On Thursday, December 17, the night after I got into town, I saw the 38-hour-old crescent moon in the western twilight over Oklahoma City, thus fulfilling the last requirement I had left for the Astronomical League‘s Lunar Club. I e-mailed in my completed log sheets on Saturday.

Instead of bringing a little scope with me, I borrowed back the one I had loaned to my brother. It’s a Synta MC90, another 90mm Maksutov-Cassegrain, but unlike my other little Mak it’s a short focal length, widefield scope. I got it out last night to show my nieces the waxing crescent moon, Jupiter, and the Pleiades.

Instructions: Speaking of the Pleiades (M45), they’re one of the best astronomical treats for a clear winter evening. Finding them is easy: look to the east after dark, and find a little knot of stars that looks a bit like a cooking pan. This is not the Little Dipper, although you’d be surprised at how many people think so on first spotting it. If you have a hard time finding the Pleiades, look for the 3/M/W of Cassiopeia, head past the Double Cluster to Perseus, and follow the lower of the two sweeping lines of stars that make up that constellation; the cluster is just off the end of the line. The Pleiades are pretty to the naked eye and probably best in binoculars. All but the widest-field scopes will have a hard time putting the whole cluster in the eyepiece, and even if you manage it, it’s prettier if you can see the cluster as a cluster, with a little open space around it. So this is one of those times that–in my opinion–binoculars trump a telescope.

If you have found the Pleiades, drop straight down (east) to find a V-shaped association of stars. These are the Hyades, another open cluster, in the constellation Taurus. One leg of the V is anchored by a big red giant star, Aldebaran, whose color is obvious even to the naked eye. You can pan around the Hyades with a scope if you like, but the cluster is so big that it really demands binoculars; binos fall right into the sweet spot of putting a lot more stars in your eyes without overly narrowing the view or getting you lost.

From the Pleiades, on to the Hyades, and farther on east you come to Orion, the most magnificent constellation in the sky. Find the three bright stars in a line that form his belt, and then three dimmer stars in another line that form the sword hanging from the belt. The middle of the three stars in the sword is not a single star at all. Rather it is M42,  the Great Nebula in Orion, a vast cloud of gas and dust, dozens of light years across, which is illuminated by the bright young stars burning within.

M42 is what I call a total object: like the moon, it looks good no matter what you use to look at it, and the more you look, the better it gets. With the naked eye, the nebula it is a faintly fuzzy star at the heart of a striking and majestic constellation. With binoculars, you’ll see a bit of nebulosity set amidst the rich starfields of Orion’s sword. In a small telescope, the full glory of the nebula starts to unfold, with glowing streamers of gas and dust spread out like an eagle’s wings. The central star will split apart into a group of four, called the Trapezium. Pour on more aperture and magnification and the view just keeps getting better. If the skies are clear and steady you may pick up a couple more stars in the Trapezium, and the surrounding clouds of gas and dust will start to look like clouds, with delicate knots and swirls.

And on it goes. You are not going to exhaust M42, not in a lifetime of observing. People with telescopes that require large trailers for transport, who have seen M42 literally thousands of times in their observing careers, still gaze into the heart of the nebula for minutes and even hours at a time. The bigger the scope, the darker the skies, the longer you look, the more there is to see.

But, hey, don’t think that if you don’t have a monster scope it’s not worth looking. Remember, M42 is a total object; it looks good at any scale. If the thought of setting up a scope in the cold and dark does not appeal, at least pop outside for a five minute session with binoculars. Make it a present to yourself.

Happy holidays!

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Mission 13: Pegasus to Andromeda

December 7, 2009

Mission Objectives: Constellation, Galaxy

Equipment: Sky map, Naked eye, Binoculars, Telescope

Required Time: 5 minutes

Related Missions: Cassiopeia and the Double Cluster

Instructions: Go outside after dark, look up high in the east, and find a big square of stars surrounding a whole lot of nuthin’. That’s the Great Square of Pegasus. If it doesn’t jump out at you, punch it up in Stellarium, print out  a free sky map, or follow the other middle leg of the Cassiopeia W, the one that doesn’t point to the Double Cluster.

The Great Square of Pegasus isn’t all in Pegasus; the star at the northeast corner actually belongs to the neighboring constellation of Andromeda. But the square is such a handy signpost that most people ignore the official constellation boundaries as set out by the International Astronomical Union.

That northeast corner star is the anchor for two almost identical chains of stars, one of which looks like a fainter copy of the other. Go from the second star in the brighter chain to the second star in the dimmer one, and then on in the same direction for an equal distance, and you’ll come to M31,  the Great Nebula in Andromeda.

M31 was named Back In The Day when the term “nebula” was used for any hazy patch in the sky. These days “nebula” means an interstellar cloud of gas and dust, any one of the many that litter the arms of spiral galaxies. They come in lots of flavors, which I won’t cover here; the important thing is that nebulae are comparatively tiny parts of galaxies.

M31, or the Andromeda Galaxy, is not just a galaxy; for stargazers in the northern hemisphere, it’s THE galaxy. From a dark site you can see it with the naked eye, and in fact at two million light years away, it is the most distant object that can be easily observed without optical aid (I qualified that with “easily” because there are a handful of more distant galaxies that can also be seen with the Mark 1 eyeball; pick up the current issue of Astronomy magazine and check out Stephen O’Meara’s column to learn more).

In binoculars, the Andromeda Galaxy looks like a pretty oval haze with a bright core. As you go from binoculars to small telescope to big telescopes, the amount of visible detail increases but the field of view usually decreases, and it can be hard or impossible to fit the whole thing into the field of view of a long focal-length telescope. Think of that, a galaxy so big and so close you can’t see it all with most scopes! It’s so close that people with monster Dobs regularly amuse themselves by picking out its globular clusters, whereas small-scope folks like me find the globs in our own galaxy to be plenty challenging.

The very, very small version of Rob Gendlers' very, very large M31 mosaic.

If you want to see M31 in all its glory, you must get over to Rob Gendler’s site and check out the stupendously huge mosaics on his galaxies page. One of his images has a resolution of 21,904 x 14,454 pixels and at least as of 2009 was the highest resolution image ever made of a spiral galaxy, period.

You may also know that the Andromeda Galaxy is destined to collide with our own Milky Way in a few billion years, setting off massive bouts of star formation as the two repeatedly pass through each other and eventually merge into something bigger and stranger, probably an elliptical but possibly a super-spiral or even a ring galaxy. Should be a pretty good show for whoever is around to see it.

Don’t wait up though. M31 is high overhead in the early evening and pretty good viewing until the wee hours. Go check it out.

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Mission 12: Nova in Eridanus

November 29, 2009

Mission Objectives: Bright Stars, Constellation, Nova

Equipment: Binoculars, Telescope

Required Time: 10 minutes

Introduction: One of the cool things about this hobby is that the sky is not unchanging. Although we can’t predict when new goodies like bright comets and novae will occur, they do come around with fair regularity. Two years ago, when I was just getting into amateur astronomy, comet 17P/Holmes suddenly blew up to naked eye visibility. I just got an AstroAlert from Sky & Telescope about a nova in the constellation Eridanus, close to the bright star Rigel in Orion.

Introduction: This is one you can’t do immediately after dark. But neither will you have to stay up obscenely late or get up obscenely early. By 9:00 or 10:00 PM, Orion should be far enough above the horizon to make this a cinch.

The first step is to locate the constellation Orion. Orion is the most striking and instantly recognizable of all constellations, so it’s just a matter of looking southeast at the right time. Find the straight line of three stars between bright red Betelgeuse and even brighter Rigel, and you’ve got it. Lots of good deep sky targets in Orion, including the incomparable Great Nebula, M42, but those are missions for other evenings.

Once you’ve located Orion, you’ll have to star-hop to the nova. From Rigel, you can follow the arc of bright stars that marks the eastern end of the constellation Eridanus (green arrow). From the third star in the chain, drop down (south) to two close stars that mark the head of the stick figure shown on these charts. Alternatively, look south of Orion to find the stars that form the outline of Lepus, the Hare, and line up the stars forming the bunny’s shoulder and the top of its head to get to the stick figure’s left foot (orange arrow).

A word about these charts: they were generated by the AAVSO, or American Association of Variable Star Observers, which has a gizmo for generating finder charts for practically all of the variable stars one might want to hunt down visually. I added the colored arrows, and the stick figure is just an asterism–a chance alignment of star–that I noticed and found useful. Star hopping is subject to individual preference, so if this way of getting there doens’t work for you, generate your own finder charts and find your own way. I don’t say that to be flip or callous; sitting down with a red flashlight, some blank finder charts, and a telescope and finding (and drawing) your own asterisms is very satisfying and a great way to learn your way around the sky.

Another thing about the charts: many stars have a two or three digit number next to them. These are not identification numbers but magnitudes, so that variable star observers can determine the brightness of their target star by comparing it to other stars in the same field. Following standard practice, the decimal points are eliminated on the charts so they can’t be confused with stars. A star with the number 81 next to it shines with a magnitude of 8.1, too faint for the naked eye but within easy reach of binoculars.

Back to the stick figure. Note that stars marking the head, heart, left hand, and left foot all have close companions, which should help you distinguish them from all the other stars out there. Once you’re sure you’ve got it, find a chain of three fainter stars trending southeast from the stick figure’s left hand. Nova Eridani 2009 forms a triangle with the outermost stars in that chain. Right now it’s shining around magnitude 8.4, so it should be almost identical in brightness to the star just below it marked 81. Don’t confuse them!

Also notice that the charts are all shown with north to the top and east to the left, just as this part of the sky looks to the naked eye, binoculars, and right angle correct image (RACI) finderscopes. Straight-through finderscopes, straight-through refractors, and Newtonian reflectors will show the sky rotated by 180 degrees. No problem, just rotate the chart upside down and keep on truckin’. Refractors and cassegrain scopes using a star diagonal will show the sky rightside up, but flipped left to right. You can either flip the image ahead of time in an image-processing program, or do it mentally in your head, or–the oldest and easiest method–turn the chart over and shine a flashlight through from the other side.

So what’s going on out there? Novae are giant thermonuclear explosions that occur when a white dwarf star accumulates enough hydrogen on its surface to undergo a chain reaction. Usually the hydrogen is slurped off the surface of a companion star, perhaps a red giant. This can happen over and over again; most novae probably “go off” once every 1000 to 100,000 years, and a few like RS Ophiuchi go off every few decades.

This explosion of hydrogen on the surface of the star is in stark contrast to a Type 1a supernova, which also involves a white dwarf accreting matter from a companion. In those supernovae, the white dwarfs accumulate enough matter to approach the Chandrasekhar limit of 1.38 solar masses, at which point carbon fusion starts in their cores, followed by oxygen fusion, followed by total destabilization of the star. The star detonates in an explosion 5 billion times as bright as the sun, with a shock wave that travels at 3% of the speed of light. Neat trick, but needless to say, one that a star can only pull off once.

Fortunately for us, Nova Eridani 2009 isn’t going anywhere. However, it will dim over the coming months, so get out there and see something new.

For more info, see the Sky & Tel writeup and the AAVSO updates here, here, and here.

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Mission 11: Cassiopeia and the Double Cluster

November 21, 2009

Mission Objectives: Constellation, Open Cluster, Bright Star

Equipment: Naked eye, Binoculars, Telescope

Required Time: 3 minutes

Instructions: Go outside after dark, face northeast, and look for the sideways W. If you’re not sure which W is which, take a free sky map. The W is Cassiopeia, which lies right smack in the middle of the winter Milky Way.

Cassiopeia is a deep sky wonderland in binoculars and telescopes. There are more star clusters than you can shake a stick at–a decent portable sky atlas will show a dozen or more. Even without an atlas, it’s an awesome area to scan around in with optics of any size.

I have a confession, though. Almost every time I go out to observe in the winter, I give Cassiopeia a quick once-over and then leave. Why? Because there’s an even better pair of clusters lurking over the border of the neighboring constellation, Perseus, and Cassiopeia is such a good pointer that you might think it was put there for that purpose. Follow the inner leg of the shallow half of the W about 2/3 of the way to the next bright star, and you’ll find the Double Cluster, NGC 869 and 884. Keep in mind the effect of sky rotation–by 8:30 PM, Cassiopeia is an M centered over the North Star, and by midnight it’s a sigma to the northwest. Adjust your expectations accordingly.

The Double Cluster is one of the finest objects in the night sky, and almost always makes it onto lists with names like “Top 10 Telescopic Targets”. I’m not going to show you any pictures of the clusters themselves, because this is one place where pictures simply don’t do justice. You’ll have to get out under the night sky and see for yourself.

Once you’ve had your mind blown by the Double Cluster, keep on cruising in the same direction and follow the chain of bright stars to Mirphak, or Alpha Persei, the brightest star in the constellation Perseus. Mirphak is surrounded by a broad field of stars called the Alpha Persei association; it is too big to fit in the field of view of most telescopes (except possibly fast focal ratio, widefield scopes like the Astroscan and StarBlast 4.5), but is instead one of the best binocular targets in the entire sky. Have a look and let me know what you think.

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Mission 10: The Great Glob

November 19, 2009

Mission Objectives: Constellation, Globular cluster

Equipment: Sky map, Naked eye, Binoculars, Telescope

Required Time: 5 minutes

Related Missions: Summer Triangle

Introduction: This is a weird time of year. The classic “summer” constellations are still visible right after sunset, and by bedtime the winter constellations–especially Orion–are already coming over the eastern horizon. Of course the globe of the sky is (relatively) unchanging and you can see an angular span of the same width on any night of the year. Nothing is actually accelerated right now. It only feels odd because of the associations these stars have for me. Say “Hercules” and I think warm summer evenings and junebugs. The Pleiades, on the other hand, conjure up memories of gloves, stocking hats, and the crystaline quality of the air on a cold winter’s night. And yet you can see these things on opposite sides of the sky at the same time!

Owing to my long hiatus this fall, I let a few of the great summer objects almost get away from me. Meanwhile, a host of excellent autumn targets are high overhead even at dusk. So we’ve got no time to waste.

Instructions: Find Vega in the western sky right after sunset, and then look below it to find the back-to-back trapezoids that make up the body of Hercules. I strongly recommend taking a planisphere or sky map, such as one of the free seasonal ones here or here. If you’re like me, you can look at the map indoors, fix the points and relationships in your mind’s eye, go outside and instantly get lost. Hercules doesn’t have any first magnitude stars to help you orient, and there are far too many medium-brightness stars, so the number of possible trapezoids you can construct is large. This is where the directions I can give break down; there is just no substitute for having the map in your hand, especially since the free ones are so good these days. See how many of the stars west of Vega you can see with the naked eye, and then draw a trail that will guide you from Vega down to where you need to go. The path you find will be the one that makes the most sense to you.

You’ll know for sure when you’ve got the right trapezoids, because 2/3 of the way along the western edge of the northern trapezoid is a fuzzy ball. This is M13, the Great Globular Cluster in Hercules. If you are under super dark skies you might just make it out with the naked eye as a dim and blurry star. Under all but the worst city lights, you can sweep between the two boundary stars and pick it up in binoculars. In 10x50s it is an attractive ball of fuzz, and in 15x70s it is a slightly larger, brighter, and more appealing ball of fuzz. In a small telescope some of M13’s 100,000 stars start to resolve, like a spill of very fine sugar on black velvet. In a big telescope, like my friend’s 16-incher, it is almost overwhelming; the eyepiece is so full of stars that it gets to be too much for the eye–and the mind–to take in. I found myself repeatedly looking away to give myself a break. That’s good stargazing.

Like M22 in Sagittarius and all other known globular clusters, M13 is old, and I mean old even for astronomy, where a five-billion-year-old star like the sun is something of a youngster. Even if all you have to see it with is binoculars, there is something special about tickling your retinas with the light of 100,000 twelve-billion-year-old suns.

Photo from APOD.

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Mission 6: Not Everyone’s Pot of Tea

September 2, 2009

Mission Objectives: Constellation, Globular Cluster, Open Cluster, Nebula

Equipment: Naked eye, Binoculars, Telescope

Required Time: 5 minutes

Related Missions: Eye of the Scorpion

Instructions: Go outside shortly after dark, face south, find Antares, and to the left/east of Scorpio, look for a teapot.

Sagittarius with lines

Yes, really. The heart of Sagittarius, allegedly the Archer, looks strikingly like a teapot. Which, I think we can all agree, is a considerably less aggressive incarnation. Once you’ve spotted it, it will be hard to avoid seeing it any time you look toward that part of the sky. It’s especially easy if you can trace Scorpio–it looks like the teapot is about to pour on the scorpion’s tail. Here’s the plain version so you can practice:

Sagittarius sans lines

Sagittarius is the thick of the summer Milky Way and contains the core of the galaxy. As a result, it is just loaded with deep sky objects (DSOs)–it hosts 15 of the 110 Messier objects, more than any other constellation. It has star clusters in its hair and hanging out of its pockets. Some are open clusters, the result of relatively recent bouts of star formation (“relatively recent” here means “within the last half-billion years or so”), but many are globular clusters or “globs”, spherical micro-galaxies of up to a million stars apiece that orbit the core of the Milky Way in an extended halo.

Sagittarius also has a stunning emission nebula, M8 or the Lagoon Nebula, which is second only to the awesome Orion Nebula (M42) for Northern Hemisphere observers. Like the Orion Nebula, the Lagoon is a site of active star formation; it is lit by the young stars it contains, and more are forming even as you read this (the Lagoon Nebula is only 4100 light years away, and it is highly unlikely that the multi-million-year process of star formation has suddenly stopped since the pyramids went up).

Sagittarius DSOs

With a clear southern sky and a pair of binoculars–which have hopefully by now been warmed ever so slightly by the brilliant light of Jupiter–you can see three beautiful DSOs that illustrate three stages in the life cycle of stars and of the galaxy itself.

Globular cluster M22 is a fuzzy ball above and to the left of the teapot–I imagine it forming a right angle with the northeastern stars of the teapot lid, as shown above. Through a telescope of less than about 6 inches aperture it will likely remain a fairly fuzzy ball, but pouring on more aperture and magnification will resolve it into something approaching this (image from Wikipedia):

M22HunterWilsonM22 is full of very old main sequence stars, and astronomers estimate its age at about 12 billion years, meaning that it has been around for more than 90% of the history of the universe. Its stars are Population II, which means that they formed shortly after the universe itself, when there had been little time for successive waves of novae and supernovae to seed the universe with heavy elements. No one knows if the Population II stars have planets; if they do, they are probably gas giants and any solid bodies are probably icy and metal-poor. If life arose in this or any globular cluster, it is hard to imagine how any of it could have become starfaring or even radio-using with few or no metals. Nobody knew this back in 1974, when Arecibo sent a “Hey, how are ya?” radio message to the globular cluster M13. M13 was chosen because it is nearby and has tons of stars; somewhat ironically, those stars are the least likely to have civilizations capable of receiving the message or responding (which may be a good thing, if you take a pessimistic view of the likely intentions of technologically superior species).

Closer to us in time of origin is the open cluster M7. It seems to me to form the right wing of an extended kite shape that is otherwise made up of the three stars that form the teapot spout. This bright ball of about 80 stars is about a thousand light years away and its oldest members are about 220 million years old–about 2% the age of those in M22. It is sobering to realize that these cosmic youngsters formed about the time that the first mammals and the first dinosaurs were getting up and running in the Late Triassic Period.

Youngest of all is M8, the aforementioned Lagoon Nebula, which sits right above the spout of the teapot like a tiny puff of steam. In cosmic terms, we’re catching M8 in the act of giving birth. A few tens of millions of years ago it was just another cloud of cosmic flotsam and probably neither bright nor particular pretty. Now it is lit from within, like a paper lantern, by its stellar offspring. In another 200 million years, M8 may look like M7 does today, with all of its ethereal clouds of gas and dust either consumed or blown away by the brash young stars that are even now forming at its heart.

So grab those binos and go see the universe–a stellar nursery (M8), primary school (M7), and retirement community (M22) await. If Jupiter blew your socks off, have a look at M22 and remember that you are looking at stars that are almost three times as old as our solar system. How often do  you get to see something 12 billion years old? Not often, I’ll wager!

…or rather, see these things if you can. There’s a reason that Sagittarius is not everyone’s pot of tea. Like Scorpio, it’s a fairly southerly constellation, which means it never gets very far above the horizon, especially for folks who live up north. Here’s what it looks like from southern England:

Sagittarius from EnglandSo if you’re farther north than about the 40th parallel, you’re probably hosed. You’ll need a clear southern horizon, sans trees, mountains, and especially the light domes of our myriad cities to get a good look. Still, give it a shot–letting the light of 70,000 12-billion-year old stars–photons that have been in transit since the end of the last ice age–fall on your retinas is worth a little effort.

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BBC article on naked eye astronomy

August 30, 2009

Milky Way over Arches NP

The BBC celebrates naked eye stargazing (hat tip to Randy).

I have mixed feelings about the piece. On one hand, it is great that such a widely-read outlet is not only featuring astronomy, but focusing on zero-equipment, zero-cost stargazing.

On the other hand, it’s a minor tragedy that their selection of objects is so out of whack with the seasons. Of the five naked-eye highlights featured in the article–Orion, Ursa Major, the Andromeda galaxy, the Pleiades, and the Milky Way–only two can be seen easily by most people right now. Those are Ursa Major (including the Big Dipper), which looks good pretty much all the time from the northern latitudes where the BBC offices are, and the Andromeda galaxy, which is just rising at sunset and well placed (up out of the near-horizon murk) by about 9:00 PM. The Pleiades don’t rise until midnight and aren’t well placed until about 2:00 AM, with Orion trailing a couple of hours behind. The Milky Way is high and bright this time of year, but tragically it is the first victim of light pollution, and if you live in or near a major metropolitan area, you can pretty much forget about seeing it unless you can travel to a dark sky site.

The list misses out on mid-summer highlights that are visible even from the city. I’ve covered several here–the stars of the Summer Triangle, especially the constellation Lyra, and Antares, the brilliant red eye of the constellation Scorpius. It’s not like “I covered them and therefore the BBC ought to have, too”. More like, “These are the best things in the sky right now, and anyone writing about introductory astronomy ought to point them out!”

The best seasonal highlight, and the one whose omission from the BBC list irks me most, is Jupiter. I haven’t written a mission about Jupiter yet, but it’s the coming thing. To the naked eye, the king of planets is the brightest star in the heavens (second only to Venus, which never strays very far from the sun), a brilliant jewel arcing across the southern sky on summer evenings. With binoculars, you can see the four Galilean moons, and even modest telescopes will reveal a few cloud bands. Last night it was overcast here but I could still see two bright patches lighting up the clouds. One was the waxing gibbous moon, just one night past first quarter, and the other was Jupiter, a small but intense spotlight off to the southeast.

So. I feel bad knocking the BBC piece. The night sky belongs to everyone and I am convinced that most people are fascinated by it and that our lives are enriched by a connection to it. Anything that gets people out there looking is therefore a good thing. I just think that arming people with a modicum of information on how to find things and what to expect is not an unreasonable expectation.

I guess that means I have to put my money where my mouth is, eh? Stand by for that Jupiter post (UPDATE: it’s up now).

Image at top from here.

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Mission 4: The Big Dipper

August 22, 2009

Mission Objectives: Constellation, Bright Stars, Multiple Stars

Equipment: Naked eye, Binoculars

Required Time: 3 minutes

Instructions: Get to a place with a clear northern horizon, look to the northwest, and find the Big Dipper. Seriously, it’s just that easy. Here, you can practice with this:

The view to the northwest right after sunset in the southern US, in Stellarium.

The view to the northwest right after sunset in the southern US, in Stellarium.

Note the little red W and N in the corners of the picture; at this time of year, the Dipper is exactly halfway between those cardinal points. If you can’t find it, make sure that it’s just after dark, see that your view isn’t blocked by clouds, trees, or mountains, and double check that you are, in fact, in the Northern Hemisphere.

The Big Dipper as a guidepost to the northern sky.

The Big Dipper as a guidepost to the northern sky.

If you can find the Dipper, you can find at least two more bright stars and have an edge on identifying their constellations. The path that is most widely known is that the two stars that make up the front end of the “pan” point unfailingly to Polaris, the North Star, around which everything else in the heavens appears to rotate. Also, you can follow the handle of the Dipper and arc to Arcturus, the brightest star in the constellation Bootes.

Like Lyra, Ursa Major has a double star treat for naked eyes and binoculars. The middle star in the handle is in fact two, Mizar and Alcor, the horse and rider. Your eyes don’t have to be particularly sharp to see that the brighter of the two, Mizar, has a dim companion. This is also a dead easy split with binoculars. A telescope working at even low magnifications of 40-50x will reveal that Mizar has another, even fainter companion, called Mizar B. Mizar was probably the first telescopic binary discovered, possibly as early as 1617, less than a decade after Galileo first aimed a telescope at the heavens. As if all of that weren’t enough, Mizar A and B are themselves both binary, although the components are too close to be separated by telescopes and can only be detected through spectroscopy.  So Mizar is a four-star system, another “double double”, all by itself.

The Big Dipper is just the rear end and oddly long tail of the constellation Ursa Major, the Great Bear. Polaris is at the end of the tail of Ursa Minor, the Little Bear. There are lots of stories about how these bears came to have such long tails–see what you can find. Because Ursa Major is so close to the celestial North Pole,  it is visible for most of the year and only dips below the horizon briefly at mid-northern latitudes. If you go far enough north, the Great Bear is visible all the time. The Greek word for bear is ‘arctos’. And so we call those far northern regions, under the eternal reign of the bear, the ‘arctic’.

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