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Number 10: The Comet and the Ring

A comet almost had to make this list, since they’re so darn pretty. But there was one this past year that, to me, was extra cool.

Periodic comet 73P/Schwassmann-Wachmann (say that three times fast) was discovered in 1930, and in 1995 it was seen to have broken up into many pieces, most likely due to heating from the Sun. The fragments passed close by the Earth once again in May 2006, where many were easily visible through binoculars (I saw them myself, both through my binocs and my ’scope).

The comet was big, bright, and passed by many astronomical showpieces… including the famous Ring Nebula, a cloud of gas a light year across ejected by a dying star. When the two were close together, astronomers Paul Martinez & Philip Brents took this spectacular shot:

...The comet looks bigger only because it’s so much closer: the Ring is actually about 10 trillion times bigger than the comet! But it’s a tad bit farther away.

Number 9: Painting the Eclipse

Lunar eclipses are fairly common: the Moon passes into the Earth’s shadow roughly once or twice per year on average. Since the Moon is bright and easy to photograph, there are zillions of lunar eclipse pictures available to view.

I thought I’d seen ‘em all, but then I saw this one and it floored me:


How cool and wonderful is that? The photographer, Laurent Laveder, set this image up very carefully, making sure that the model was placed just so when the Moon was just starting to be eaten by the circular edge of the Earth’s shadow. The result was this very clever tongue-in-cheek photo. I love it! He has many more images on his site worth checking out, too.

Number 8: The Tarantula Writ Large

Our Milky Way Galaxy is a giant spiral collection of stars, gas, and dust. It has many smaller satellite galaxies, and one of them is the Large Magellanic Cloud, or LMC. The LMC is a fuzzy cloud-like object easily visible to the naked eye if you happen to be far enough south of the Equator (I saw it with my own eyes from Canberra, Australia in 2004). Through a telescope, though, the LMC is dominated by a cloud of gas called the Tarantula Nebula, perhaps the most active stellar nursery known.

You’ve probably seen images of the Orion Nebula, right? At 1500 light years away, it’s one of the brightest nebulae in the Milky Way, and is easily visible to the unaided eye. It’s about 30 light years across.

The Tarantula, however, is 160,000 light years away, and yet is still about as bright to the eye as the Orion Nebula. That’s because it’s frakking huge: it’s something like 1700 light years across, fifty times Orion’s size! If the Tarantula were placed at the distance of the Orion nebula, it would fill half the sky.

That’s big.

And so is this next image. The good folks at the European Southern Observatory stitched together several images of the Tarantula to make a mosaic of it that has 256 million pixels. Let’s see your store-bought camera do that!

This is a very, very compressed image of the big one. You could download an insanely monstrous 211 Mb 9000 x 8000 pixel image, but I recommend you go to their zoomable image of it instead, and tour around it. See if you can spot Supernova 1987A, a star which blew up and eventually led to me getting my PhD.

Number 5: The Shuttle, the ISS, and the Sun

I still think it’s funny that most people are unaware that they can see man-made satellites easily with the naked eye. There are even websites that can tell you when a given satellite will pass near you!

The Shuttle, when it’s up, is a pretty bright object, as is the International Space Station. So if you do your homework and plan your observation extremely carefully, you just might make my Top Ten list.

Thierry Legault did just that. Not only did he get a picture of the Shuttle and the ISS, he nailed them while, from his viewing point, they were passing directly in front of the Sun.


This shot is simply stunning, and shows a tremendous effort in planning, timing, and execution. The picture was taken on September 17, 2006, less than an hour after Atlantis had undocked from the ISS. By capturing them in silhouette against the Sun, he could take such a short exposure that any atmospheric distortion was frozen out. This means he got incredible detail in his picture.
But try not to get lost. It’s a big place.

Number 4: Direct Evidence of Dark Matter

This next picture takes a moment to set up, so please forgive me. Plus, I like to lecture sometimes.

As I was perusing images, I realized I didn’t have many that had strong scientific value, which was ironic. But that happens: most scientific images aren’t published because they’re pretty, and pretty pictures sometimes only get in the news because they’re pretty. But there was one image this year that has both beauty and a far deeper scientific significance.

It’s been known for decades that there is a lot of dark stuff out in space, between galaxies. We see its effects on the way galaxies rotate, and the way they behave when they live in clusters (like a city of galaxies). We know that this dark matter is ten times as common as regular matter (like the stuff we are made of: atoms of hydrogen, carbon, oxygen and so forth), but it was undetectable, so it was somehow different than normal matter. But how, exactly? No one was sure.

One theory was that dark matter was made of weird particles that could interact with normal matter or other dark matter through gravity, but that was it. In other words, two colliding clouds of dark matter could pass right though each other like ghosts.

But how do you detect something like that? One way is through gravitational lensing. Matter has gravity, and gravity bends light. So if matter, even dark matter, gets between you and some distant object, it can act like a lens, distorting the light from the more distant object. By mapping out those distortions you can "see" dark matter.

So you know what those clever astronomers did? They looked at two colliding clusters of galaxies, which together are called the Bullet Cluster. Galaxy clusters have lots of gas pervading them, like fog in a city. When the clusters collided, the gas from each cluster smacked into the other head-on, grinding them to a halt. But if the dark matter is really this ethereal stuff it would keep on going, undeterred. If this were the case, you’d see the normal matter from the cluster closer to the center, with the dark matter on the outside.

And behind door number two…



Voila! The pinkish light is coming from the normal gas in the cluster. The dark matter reveals itself through its gravitational distortion of more distant objects, which is colored blue here. And look! The dark matter is on the outside, and the normal matter on the inside, just as predicted!

To an astronomer, this is completely convincing evidence that dark matter is real, and that the majority of the Universe is made up of stuff we simply don’t understand. What is it? Beats me, and it beats a lot of other scientists, too.

I love mysteries! That means there’s more to learn.

Number 3: Solar Shock Wave

The next image on my list makes me a little sore. When it was released I was busy and figured it wouldn’t be that interesting. I was completely wrong.

The Sun has a powerful magnetic field. The surface of the Sun is so hot that the atoms of gas have their electrons stripped off (the atoms are ionized), and this in turn makes them susceptible to those magnetic fields. In fact, the field is coupled with the matter: the gas follows the shape of the magnetic field lines, and as the gas moves the field lines also follows the gas. As the gas churns and boils on the surface, the field lines get all tangled up. A lot of energy gets squeezed in a tight space, and when that happens the magnetic field lines can suddenly and catastrophically reconnect, releasing vast amounts of energy in a solar flare.

On December 6, 2006, a big flare detonated on the Sun. The release of energy screamed outward over the surface, expanding in a circle. Astronomers at the National Solar Observatory caught this expanding shock wave in the act:

The fuzzy white ring is the expanding wave. The scale here is numbing: the Sun is 1.7 million kilometers across, so this ring was hundreds of thousands of kilometers in diameter. Heck, just the width of the ring is far larger than the Earth!

So why is this one of my top picks for 2006? After all, the still image doesn’t look like much! Ah, but the astronomers at NSO strung together a series of images into a dynamite animation. It’s totally cool. I couldn’t find the total energy released in this flare, but a typical big flare might blow off 1025 Joules… which is 10% of the total energy emitted by the Sun every second.

Still not sure how much that is? Think of it this way: a big hydrogen bomb might have a yield of about 10^16 Joules, so this flare was the equivalent of one billion hydrogen bombs.

Yikes.

See why I picked this as number 3?


And the Number One Astronomy Picture of 2006 is…


Saturn from Cassini, back lit by the Sun with a glow in the background

Saturn.

What else could it possibly have been?

This image has it all. It’s of a familiar object, seen in an unfamiliar way: back-lit by the Sun, a view impossible from Earth. It shows the whole planet, a rarity from space missions. The image shows very faint details and has very high resolution, a must.

But there is sheer artistry at work here. The colors, the lighting… I love the sun splash in the lower left limb of the planet, and the fans of ethereal mistiness shooting out from the rings. The shading on the planet itself is lovely, while the rings provide a geometric symmetry that is very appealing to the eye.

All this is necessary for the image to be the best, and together they may even be sufficient. But like all true winners, it has that extra addition, the over-the-top detail that pushes it into "all-time" status:




That dot in the center of the image is the Earth. It’s us. Cassini was nearly one billion miles from us when it took this image, orbiting a giant ball of gas as exotic and alien as any place we can imagine. From such a terribly removed location, the entire Earth is reduced to a single point of light, just one among an anonymous many as seen from our robotic proxy as our generation, for the first time in all of history, seeks out our neighborhood and takes a really good look.

That’s why this is the best astronomy image of 2006. And it’s one of the best of all time.

[...]Seen from our robotic proxy as our generation, for the first time in all of history, seeks out our neighborhood and takes a really good look.

Beowulf wrote:The images don't load because you fail at life.