Twelve million light years away, in the heart of the M82 galaxy, a binary star system detonated. One white dwarf star had gradually increased in density until matter, spit onto its surface by its larger twin, piled up past a point of no return. Then, at the core of the white dwarf, carbon and oxygen fused until they exploded in a chaotic fit of light and energy.
Today, 12 million years later, many Earthlings can see this explosion in the night sky. Last night excited reports began to pour in with details about the closest supernova to Earth we've seen since the 1980s. Beginning with a team from Russia and then Japan, astronomers began snapping confirmation images and comparing notes, rushing to learn more about the explosion currently known by awkward moniker of PSN J09554214+6940260.
"It's a really rare and interesting event—a once-in-a-century opportunity to study this type of supernova in exquisite detail," says Fionna Harrison, a professor of physics and astronomy at the California Institute of Technology (Caltech).
Supernovae aren't simply incredible explosions; they represent a cosmic yard stick of sorts. Cosmologists rely on the light produced by supernovae to map out the contours of distant galaxies. Type Ia supernovae, like this one, are of particular interest, because their explosions are the most predictable, and often the brightest, events in the sky. Because Ia supernovae give off a standard amount of light based on their mass, scientists can calculate their distance from Earth.
Our current cosmological maps rely on how bright astronomers assume supernovae to be. But these calculations are fraught with some uncertainty, since determining the true brightness of an object millions of light years away is tricky business. The ideal solution to this problem would be to find a type Ia supernova so close by that astronomers could analyze the star before and after detonation to determine exact brightness.
"Controlled experiments are hard to do in astronomy," says Brad Tucker, an astronomer at the University of California, Berkeley. "But in this case we can calibrate and improve all of those measurements by observing the star before it explodes and after."
The opportunity to study a local supernova has prompted astronomers to deploy some of their most powerful telescopes. Astronomers at Caltech will turn their x-ray telescope NuSTAR toward M82 tonight, in an attempt to study the radiation produced by the blast. "Looking at supernovae is one of the things NuSTAR was designed to do," Harrison says. "We will be basically looking there continuously for the next couple of weeks."
For the more casual stargazer, this nearby supernova is an unparalleled opportunity to observe a cosmic explosion relatively close to home. Although about 50 supernovae detonate every second, Tucker says, finding one close enough to spy with nothing more than a pair of binoculars is a rare treat. Amateur astronomers should be able to see the supernova at its zenith in early February by directing their binoculars between the Little Dipper and the Big Dipper.
Meanwhile, pro astronomers will be collecting data that could fundamentally change how we measure distance in space. "This is a big chance to not only improve our understanding of physics, how stars are formed and how stars die, but also to improve the tools of cosmology that measure the properties of the universe," Tucker says.