This little animation may not look all that exciting at first… Until you realise what it is. This, captured by NASA’s twin STEREO spacecraft, is the first ever video recording of a nova occurring!
You know those home videos you see on TV sometimes? The ones where the person with the camera suddenly stops paying attention to what they’re supposed to be filming and starts paying attention to some interesting thing happening in the background? Well that’s basically what this is. If spacecraft made home videos.★ And this one is actually, you know… interesting, instead of being someone falling over or a UFO that turns out to be a satellite. Yes. By the way, if you’re not a fan of gif animations, the original is on YouTube here.
Anyway, a nova is rather an interesting event. A nova is a stellar explosion caused by a greedy white dwarf star stealing material from a larger stellar neighbour. If a white dwarf orbits too closely to a larger star, it can pull material from that star’s outer layers. Because white dwarfs are strange little things made of highly condensed matter, they have rather severe surface gravity. Severe enough that when sufficient amounts of material build up on the white dwarf’s surface, they can suddenly ignite in a brief but fairly potent explosion of nuclear fusion which blasts the dwarf’s entire surface away into surrounding space. This explosion makes for a sudden tremendously bright light, seen by astronomers as a star seeming to suddenly flare into existence. Because it appears to be a new star, the classical astronomers referred to these things as “nova stellae” or new stars — which is where the modern name of nova comes from.☀
Even though the nova appears to be brightening before your eyes, this video is actually timelapsed. It was taken over the course of several hours. Catching one in a spacey home video like this is still cool though, because it doesn’t normally happen. Novae are spontaneous and unpredictable little things. To see something like this, you need to be looking in the right direction at the right time, and as it happens, the STEREO craft were. Serendipity is a wonderful thing…
This video gives a rather nice animation of exactly what’s going on when novae occur. This in particular is of the Z Camelopardalis system — a “cataclysmic variable” where nova-type outbursts occur fairly frequently.
Exposive gratitude to io9 for my source this time! Also, if (like me) you have a penchant for looking at optical spectra of things, there’s a thread devoted to novae on the galaxyzoo forums. Mmmm… delicious data!
★ While they were supposed to be observing the Sun, too. Honestly, you just can’t get the craft these days…
☀The name “supernova” seems pretty obvious really given it’s also a stellar explosion, only immensely more powerful!