It’s been a while since I’ve done a Monday spiral, so here’s a great example of one: the nearby beauty M96.
[Click to oooh-and-ahhhhhenate.]
There’s some nifty stuff here. M96 is about 36 million light years away — relatively close by, for a big galaxy — and is part of a small group of galaxies called (can you guess?) the M96 Group. This is a small collection of a dozen or so galaxies, much like the small group of galaxies to which we belong, called (can you guess that one?) the Local Group. M96 is about the same size as our galaxy, too: roughly 100,000 light years across.
The spiral shape is not as symmetric as usually seen in these types of galaxies, and that’s almost certainly due to gravitational interactions with the other galaxies in the group (which are spread out enough not to be seen in this close-up). You can see lots of dark dust swirling around the center of the galaxy, blocking the light from stars behind it. You can see more on the right than on the left, indicating the right side of this galaxy is the side of the galaxy nearer to us. But that top looping arm is way out of proportion to the other side of the galaxy, so it’s probably been tugged out due to the other galaxies in the group. You can see clumpy regions of blue along its length; that’s where stars are being born, blasting out lots of ultraviolet light and causing the surrounding gas to glow.
I think my favorite part of this picture, though, is the reddish edge-on spiral galaxy located in the upper left, almost perfectly aligned with the spiral arm of M96! This is certainly a coincidence; the edge-on galaxy is probably much farther away. The red tinge to it supports that idea; dust in the arm of M96 would absorb bluer light from the more distant galaxy, letting the red light through.
Measuring its size off my screen, I get that it’s about 1/5th the length of M96. If it’s the same size physically as M96, then it’s probably 5 or so times farther away, maybe 150 – 200 million light years off. That’s actually a pretty good distance away. Yet in this image details can still be seen; that’s the advantage of using the colossal 8-meter mirror on the Very Large Telescope! You can still get a pretty clear picture of fantastically distant objects, even when they’re partially obscured by foreground objects.
And you get a gorgeous picture out of it, too.
Image credit: ESO/Oleg Maliy