The Sciences

Lonely galaxy is lonely. But it ate its friends.

Bad AstronomyBy Phil PlaitMar 8, 2010 6:00 PM


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Do cannibals have friends? I imagine some must... unless they have them over for dinner. Just like the giant elliptical galaxy ESO 306-17, which you can see in this gorgeous Hubble picture:

[Click to embiggen, or grab the monster 3800 x 3800 pixel version. They have wallpapers, too.] ESO 306-17 sits about a billion light years from Earth. In this picture it looks like it's surrounded by other galaxies, but that's an illusion: all the other galaxies you see here are either much closer to us or much farther away. ESO 306-17 is actually a loner, sitting all by itself in space.[Update: Or almost all alone; Michael West, who led the team that took these images, tells me the little elliptical at the bottom left of ESO 306-17 may be interacting with it. It's difficult to tell; but what is certain is that there are very few galaxies near the big one, far fewer than you'd expect.] How can a galaxy get this big and yet be sitting in a giant void? Easy. It ate all the neighbors. We know this is how galaxies grow in size, and is even why the Milky Way is a giant among galaxies. Like our galaxy, ESO 306-17 has a lot of globular clusters around it, just as you'd expect if it ate a bunch of other galaxies. When I downloaded the bigger image, I noticed this weird galaxy on the left:

Wow. I'm guessing that long stretched-out junk is a small galaxy that got shredded, maybe after a close pass to that spiral. I thought for a moment the spiral might be active -- that is, the black hole in its core was actively eating matter and ejecting long jets of gas and light -- but the core itself is not bright, as you'd expect. Plus, the material is lumpy and irregular, more indicative of a cosmic collision in progress. It's unrelated to the elliptical, but still very cool. I really urge you to download the big image and take a nice, long look at it. There's a lot to see, and it's all really beautiful. Image credit: NASA, ESA and Michael West (ESO)

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