Lonely galaxy is lonely. But it ate its friends.

Lonely galaxy is lonely. But it ate its friends.

Lonely galaxy is lonely. But it ate its friends.

Bad Astronomy
The entire universe in blog form
March 8 2010 7:00 AM

Lonely galaxy is lonely. But it ate its friends.

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:

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

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ESO-306-17

[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.

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When I downloaded the bigger image, I noticed this weird galaxy on the left:

ESO-306-17_detail

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)