I'm not exactly a wishy-washy kind of guy, but choosing this year's Top Ten Astronomy pictures was really tough. First, there are literally hundreds of images to go through. Maybe thousands. I can usually narrow that choice down to a few dozen. But then I'll have three pictures of the same sort of thing: colliding galaxies, or Jupiter's moons, or whatever. Then I have to figure which of those three is the best. Framing, color, science, simple devastating impact... whatever criteria I can use. Then I have to make sure I can use the one I pick. Some images are from amateur astronomers, and I need to know if they are copyrighted, and what credit to give.
For whatever reason, some images just didn't make the cut. I never heard back from the owner, the image wasn't high enough resolution, whatever. In some cases they were too similar to last year's picks (I may ease up on that next time). For others, I just screwed up; I thought they were from 2006, or I simply never saw the image in the first place.
The following pictures are one that fall in this category. They are all gorgeous, of course, and very cool scientifically, but they just didn't make my Top Ten. Still, I think you'll like them! Clicking on them will take you to a high-resolution version from the original image site. Some are extremely high-res and totally amazing.
After I had compiled my final Top Ten list and written everything up, I realized with utter horror (no exaggeration) that not one Cassini image was on the list! And this, with a) the Saturn image being my #1 pick last year, and b) Carolyn Porco -- the Cassini imaging team leader -- being a friend of mine! The reason I left Saturn off were manyfold, and I tried, oh I tried. Here are the pictures I considered.
This spectacular Cassini image of the crescent Saturn is impossible to see from Earth; the orbiter was high over the plane of the rings, capturing this mesmerizing view. I love this picture, and was one of my first choices for the Top Ten. But then I realized it was a little too much like last year's winner, so I cut it. That hurt to do.
Saturn's moons are weird, but none weirder than Iapetus. First, it has two totally different hemispheres; the leading gone (the one that faces into its direction of travel as it orbits the ringed planet) is very dark, and the trailing hemisphere is very bright. This is because of the junk it slams into as it moves around Saturn. Also, the moon has a giant raised ridge around its equator, kilometers high. Theories abound about it (including some silly pseudoscience ones, of course), but its exact origin is still something of a mystery. This picture is a mosaic of several smaller images made by Cassini. I didn't include it on my list because I'm an idiot, and thought it was from 2006 (even though it was on my blog recently)! It was Fraser from Universe Today who told me (too late) that it was recent. Figures. Obviously, this would have made the cut had I been thinking.
In February, a rocket booster exploded high in the sky over Australia. Robert McNaught, famed comet hunter, caught it on camera and created a short animation as the debris cloud moved across the sky as it orbited the Earth. You just don't see stuff like this every day, and it's totally cool. You can even see small streaks from the solid debris! This image is from Space Weather, which is a great daily stop for amazing images and info.
Comet McNaught from STEREO
Speaking of McNaught...
Comet McNaught graced our skies in January 2007, and was magnificent. It was near the Sun, and so bright it was easily visible in broad daylight! I took many terrible pictures of it, but my favorite is this one from NASA's STEREO spacecraft. Thing is, I already had a STEREO animation on my Top Ten list, and another comet as well, so I dropped this one. There are dozens, hundreds of incredible images of McNaught on the web; my second favorite is this one from McNaught, the man himself. APOD has many more, too.
The Moon Eats Saturn
I love this multiple image of Saturn passing behind the Moon. It comes from Peter Lawrence via LPOD, the Lunar Picture of the Day. It's rare, but sometimes the Moon appears to pass directly in front of a planet. Peter took a series of images and made this composite. It's very cool, and gives you a sense of depth to the solar system. Saturn is huge, but it's a long way away.
Chaos in Cluster Abell S0470
How many Hubble images can you have in a Top Ten list? Maybe next year I'll expand the list to 15. That way I won't have to leave out pictures like this one, of the galaxy cluster Abell S0740. Pictures like this floor me; the sheer variety, complexity, and beauty of galaxies in a cluster always brings me to a standstill. Just examining the image can tell you so much about galaxies behave in such an environment! Careful analysis also reveals a lot of information about the way the Universe itself behaves, and that's why we do this, isn't it? That, and to simply gape at the pageantry of the cosmos.
The Milky Way Galaxy is lousy with dense clouds of gas and dust, stellar nurseries where stars are born. This phenomenal Hubble mosaic has so much going on in it that it's hard to know where to start, and it's harder to know where to stop! That link will take you to a lengthy description I wrote, and had a huge amount of fun putting together. Scroll to the bottom for one of my favorite astronomical images of all time.
Barred for Life
I Zwicky 18
... or this picture of I Zwicky 18. This galaxy is cool for more than just its odd beauty: it was thought to be a young galaxy, but it turns out to have some very old stars in it. It is also 59 million light years away; the observations making this image showed it to be 10 million light years farther away than previously thought.
HAWK-1 and the Stellar Cocoon
This image from the Very Large Telescope in Chile is very cool, showing dust and gas in a star-forming region. I discussed it in depth in an earlier blog entry. It's nice, but not quite what I was looking for for my Top Ten. Still... cool.
I love whimsical pictures, too, and this one kills me. The effort that went into it must have been phenomenal; the Moon is actually very small in a camera, and I would think that if the tripod had even been bumped slightly it would have totally screwed this image up. Not to mention the timing! Wow.
Spitzer maps a distant planet
In 1995, the first planet was discovered orbiting a sun-like star. We've come a long way: well over 200 have now been found; one has been directly imaged, and some have even had their atmosphere detected! This image is the very first temperature map ever made of an exoplanet, in this case HD 189733b, which orbits its star so closely that it is extremely hot. Spitzer can detect that heat, and as the planet orbits its star we see different aspects of it. By mapping the amount of heat detected very carefully over time, astronomers were able to create this temperature map of the planet. The hot spot is the part of the planet that permanently faces the star (where it's always high noon), and fierce winds distribute that heat around the rest of the planet.
Mapping Dark Matter
It is no exaggeration to say that this is one of the most important maps ever made: a three-dimensional layout of dark matter in the Universe. Dark matter is invisible, but for decades has been known to exist. An extraordinary series of observations led to astronomers being able to map out its location in the Universe. Distance increases to the right, and, since we see more distant objects as they were in the past, we are actually getting a timeline of the cosmos. Note how the dark matter is smoother back when the Universe was young; over billions of years it has fragmented and aided the development of the galaxies and clusters we see today. This was an incredible confirmation of dark matter science and theory!
The Helix Nebula is a favorite: it's a planetary nebula, a cloud of gas created when a dying star sheds its outer layers, which expand outward in dramatic fashion. Spitzer Space Telescope captured this incredible view of it. It's possible the Sun will look like this in a few billion years, when it runs out of hydrogen fuel in its core and starts its final paroxysms... though some current reading I have done indicates the Sun won't be bright enough to light up the gas. It will still blow off its envelope, but the gas won't be lit up in this way. Too bad, I suppose; aliens viewing our eventual demise won't get such a pretty show.
The US and Russia are no longer the only countries to have sent probes to the Moon, Japan now belongs to this exclusive club (as do India and China as well). The Japanese orbiter Kaguya captured this incredible series of images as the Earth appeared to set over the limb of the Moon. It doesn't look real! But don't tell Bart Sibrel.
Does this count as astronomy? Maybe. But after traveling millions of light years across the Universe, sometimes the best sight of all is the approach of home.
And there you go. Next year, well, we'll see. Making the Top Ten cut is so hard I may very well expand the list. If you are an amateur astronomer -- or a pro -- better get cracking! Obviously, the competition is fierce. But I'm already looking forward to seeing what will rise over the horizon in 2008.