Monday, April 2, 2012

Supernova Hat Trick.

The last year has really been pretty good for astronomers studying supernovae. I glossed over it in my post about them, but there is still much we don't know about supernovae. This is mainly because they're so rare. Basically, the more massive the star, the fewer of them there are. Stars large enough to go supernova make up only a tiny fraction of the stars in a galaxy, much less than 1%. (For comparison, our own Sun, often called a fairly average star, is still larger than 80% of the stars in the universe, and star don't really go supernova until they're nearly ten times more massive than that.) Typically in a spiral galaxy like the Milky Way one supernova will go off on average every fifty to a hundred years. However, there a lot of galaxies out there, so if you watch enough galaxies frequently enough you should catch one going off eventually. This is the basis behind all systematic supernova hunts, which can image tens of thousands of galaxies night after night.

This sounds like good news for supernova hunters, but the hidden catch is that many (most) of these supernovae are very, very far away, simply because the majority of galaxies in the universe are very, very far away. This makes them hard to study and analyze because they're hard to see well so far away. It's not often that we get supernova within a few dozen million light-years or so, but in the space of the last ten months we've had three of them go off within 40 million light-years, all three in bright galaxies on the Messier list. And no, despite the date of this post, I'm not making this up.

In June we had SN2011dh go off in M51, 23\(\pm\)4 million light-years away, then in September SN2011fe went off in M101 at 20.9\(\pm\)1.8 million light-years. Finally, on March 16, supernova SN2012aw was discovered in M95, about 32.6\(\pm\)1.4 million light-years away.

I wasn't able to get a picture of it before due to bad weather, but last Thursday the stars finally aligned for me (or, rather, the clouds finally got out of the way) and I was able get the picture you see below:

Messier 95 (bottom, with SN2012aw) and Messier 96 (top) in Leo. North is to the left.

At the top of the picture you can see Messier 96, a galaxy close to M95. At the bottom you can see M95, with SN2012aw marked. Remember, every other star you see in this picture is part of the Milky Way, and SN2012aw is outshining many of them, despite being over three thousand times farther away. That's how powerful a supernova is (not to mention that it's still putting out an amount of light comparable to the rest of M95, two weeks after it went off).

Also, I just wanted to mention that I think the central detail on M95 is really pretty. That's a pretty nice ring of star formation there around the central bar.

2 comments:

  1. Great shot! Have you ever thought about trying to image a quasar? It's something I had always thought about doing, but never got to it. It might be fun just to have a picture of light that's 13 billion years old!

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  2. I hadn't considered it before, but I'll think about it. It would definitely be cool! The brightest one, C3 273, is in Virgo, and only about one magnitude fainter than M95 (12.9 vs. 11.4), so it is both theoretically possible and temporally favorable right now. Now if only the weather would actually cooperate with me...

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