AAS Report #3: Things that go boom!

Note: My body was the target of a vicious but thankfully short-lived viral attack on Sunday. I was totally out of it for a full day... and the less you know about this the better. It did keep me offline -- literally -- but I'm all better now and ready to blog. Good thing, too: there is a lot of cool stuff coming out of this meeting! It's a fact of life that some stars explode. Actually, it's a good thing: when stars explode they create and scatter the heavy elements that create us. The iron in your blood and the calcium in your bones were created in a supernova! So it's important to study these objects, so we can better understand our origins. But it's also fun! Stars explode! Bang! Cool! Today there were three press releases about supernovae. All three were surprising to me, and pretty interesting. 1) Kepler's Supernova was a Type Ia OK, so that title doesn't thrill you. But that simple statement is actually the answer to a long-standing mystery. Ready for this? OK, sit back... You may already know that massive stars -- stars with something like 20 or more times the mass of the Sun -- explode when they end their lives. You may not know that for thousands of years before this, they blow off a sort of super-solar wind, dumping quite a bit of gas into space around them. So eventually the star explodes and the outer layers blow outwards at tremendous speed, while the core collapses. The outer parts slam into the gas previously ejected by the star's wind, form all kinds of weird and wonderful shapes, and become the supernova remnant (sometimes called the debris). The collapsed core turns into either an ultradense neutron star or a black hole. This is called a Type II (pronounced "two") supernova. So duh, there must be a Type I. Originally, the distinction between a I and a II was that IIs had hydrogen in their spectrum (meaning there is a lot of hydrogen gas around the star), while Is didn't. Eventually, the classification was found to be more complicated (isn't everything?), and there had to be sub-classes, like Ia, Ib, and so on. It's now understood that a Ia is when a white dwarf explodes. In fact, I've explained this before. Save me some writing, read the first part of that link, and then come back here. I'll wait. <crickets> OK, done? Now you understand how white dwarfs explode. So, you'd think if you found a star that had exploded say, 400 years ago, it would be easy to tell if it was from a massive star or from a white dwarf. But it turns out it ain't. I give you Kepler's Supernova: