OK, dumb title. But look at this:
On the left is a field of random galaxies (labeled a through d). On the right is the same field, showing a new blip of light.
Not much to look at, is it? It's a supernova, an exploding star; it went off after the first image was taken. It doesn't look like much, but that's because it's 4.7 billion freaking light years away.
When a star explodes, it's a titanic event of mind-numbing violence. It can emit as much light in a few days as the Sun does over its entire lifetime. Octillions of tons of gas explode outward at thousands of miles per second, and the radiation emitted can fry planets from trillions of miles away.
And this was no ordinary supernova. It's the most powerful ever detected, twice as powerful as the most luminous ever seen before. It was found by astronomer Robert Quimby at the McDonald Observatory using
a monster 10-meter telescope. a relatively modest 18" telescope, then followed up with a monster 10-meter.
In general, by taking a spectrum of the object you can find its distance. Supernovae tend to emit light at specific wavelengths (colors) just like a neon bulb does. Since the Universe is expanding, the lines redshift, getting longer wavelengths the farther away the object is. If you can identify a few lines (some from oxygen, some from hydrogen, etc.) you can get the distance of the object fairly accurately. Initially, Quimby only saw one line, and wasn't sure which one it was, so the distance wasn't well-determined. He knew that if it were [OIII] (a green line emitted by oxygen) the supernova was the way the heck far away. It wasn't until followup observations identified a magnesium line with the same redshift that the distance was nailed: 4.7 billion light years.
When that's taken into account, Supernova 2005ap (or just SN2005ap) is the most powerful ever, dwarfing the previous record holder (SN2006gy, also found by Quimby).
The star that blew up was a bruiser, probably several dozen times the mass of the Sun. When it ran out of fuel in its core, the core collapsed. This sent out countless neutrinos (subatomic particles) like a bomb, which blew up the outer layers of the star.
What's interesting is that it was thought just a few years ago that a supernova couldn't get this strong. But SN2006gy last year and now SN2005ap make it clear that they do happen. It means there are some things about supernovae we still don't fully understand. The idea now is that the core of the impending supernova gets so hot that it creates antimatter, and this adds energy to the explosion. I know it sounds weird, but in fact we see this production of antimatter (in the form of anti-electrons called positrons) all the time. Conditions in the cores of some stars are ripe for this kind of production, so it's a likely suspect behind these monster explosions.
Supernovae are incredibly complicated, and even though many go off each year that we can study, the details of the explosion mechanism remain elusive. We love it when ones in the extreme go off like this, because it tests the ideas at their limits, and sometimes that makes it easier to figure out what's going on. And sometimes it makes it worse! But this instance of incredibly high temperatures, pressures, and energies will be eagerly inserted into new models of supernovae, and we'll be one step closer to understanding them.