Apparently, lots of people were disappointed by NASA’s cryptic press release only being about a supernova. In our own galaxy. That’s right, only a supernova. It’s ok, it’s only one of the most powerful events in the naturally occurring universe, emitting x-rays because it’s still millions of degrees in temperature, estimated at a mere 140 years old. In fact I saw five of them last week. Possibly. But I should pry myself away from mocking everyone who thought NASA had found aliens. To be fair though, a press release saying essentially “We’ve found something cool, but we won’t tell you what it is yet” is bound to get people a bit hyped, especially out here on the internet. And let’s face it, we’d all quite like NASA to find aliens. I know I would!
So… a supernova? What’s this all about? Well, the Milky Way has a lot of stars – around 200 billion – and a small percentage of these are thought to be large enough to end their lives in a dramatic supernova. Statistically, we should have about 3 every century, and a supernova is so bright that they outshine their host galaxies from the other side of the universe. Any supernova in our own galaxy should be visible with the naked eye, probably during daytime… right? The thing is, none have actually been seen since 1604 when Kepler had the good fortune to study one. Indeed, another had been studied by Tycho Brahe just 32 years earlier. So, now that we have ridiculously powerful telescopes using forms of light they didn’t yet know existed back then, where have they all gone?
If this one is anything to go by, they’ve all been hidden by dust. Apparently, it isn’t the first time either, as no one saw the explosion that created Cassiopeia A roughly 300 years ago. The Milky Way, you see, has lots of dust (the black patchy stuff in the image below). Actually, most galaxies do. Unless you’re some kind of solid state astrochemist who actually studies it, it can be quite annoying for astronomers who want to see what’s on the other side of it all. That’s why that (curiously firefoxy) image to the right is actually made from radio and x-ray images (both can penetrate dust quite easily).
Interestingly, they’ve actually known about supernova G1.9+0.3, as it’s inspiringly known, since 1985. It’s just that until recently, no one really appreciated what they were looking at. In fact, no one realised until they found out how quickly it was expanding. 0.72% in size each year might not sound like a lot, but this thing is quite far away. It’s actually expanding outwards at around 14,000 kilometres every second, or 5% the speed of light! Let me put that into perspective here — the diameter of planet Earth is only 12,000 kilometres. This expanding cloud of supernovic detritus could envelope our planet in less than a second!
Obviously, this little explodey star is big news for NASA, who have clearly been itching to look at a recent one for years. Perhaps understandably though, not everyone shares their excitement. At least maybe not to the same degree.
Actually, I’m looking forward to seeing what people can figure out from this. Recently, astronomers have been questioning if they really know what they think they know about supernovae. Seeing as no one’s ever witnessed one close up as it’s happened, the best theories we have are, well… theories. They haven’t even mentioned what type of supernova this is yet (oh yes, there are a few different kinds of supernova).
I’m definitely looking forward to reading more about this…