Tuesday, August 21, 2007

Mira the Comet-Star

I've been away in Pittsburgh for the weekend, excitedly getting more stuff than the two suitcases-worth I've been living on the past few months, which explains the few posts here. But one interesting thing happened: while seeing Superbad with my brother and his friends (which is actually good if you're in an American Pie-ish frame of mind), one of the friends asked me if I'd heard of the newly discovered star he'd heard about on the news. "It has a wake of planets and dust behind it as it plows through space!" he explained, which sounded interesting so I promised to look into it.

So today after I got back to campus and unpacked somewhat, I went to good old APOD and the blogosphere to see what was up. It turns out all the fuss is about Mira, which isn't newly discovered at all: it's been known for centuries to astronomers because it changes brightness dramatically over the course of 400-odd days, and this was rather interesting during the days when the stars were believed to never change. We now know that Mira does this is because it's a star near the end of its life, very similar to what our sun will be like someday, and stars at this stage pulsate as their outer layers expand and contract.

What is newly discovered about Mira is its cometlike tail that was recently discovered through a UV image taken with the GALEX satellite (seen above). The tail you see in the image is about 13 light years long, and has about 3,000 times more mass than the Earth. This came about because Mira is plowing through space at a breakneck speed of 130 km/s (our Sun, for comparison, moves at a glacial 20km/s), so the outer layers of the star are being stripped away and left in Mira's wake, and which show up in UV.

I rather like this discovery, by the way. I like it because it shows that even though you can look at something for hundreds of years and still not know all the secrets! You're really in for the long term when studying the universe...