On March 16 professional astronomers and amateur observers detected the bright point of light on the outskirts of M95, a barred spiral galaxy in the constellation Leo, the lion. Since then, various teams have been watching the object closely.
Based on observations from around the world, the International Astronomical Union announced on Tuesday that the light is definitely an exploded star, now called SN 2012aw.
Most supernovae are discovered in much more distant galaxies, so the explosions are not detected until they've reached close to maximum brightness, said Ulisse Munari of Italy's National Institute of Astrophysics.
But the new supernova is in a galaxy just 37 million light-years away—practically next door in astronomical terms.
"The detection threshold has been broken already," Munari added, and the supernova should get even brighter in the coming days.
What's more, some amateur astronomers happened to be taking pictures of M95 before SN 2012aw appeared.
Combined with an ongoing catalog of new images, the older shots will allow astronomers to study the very early stages of a supernova—perhaps helping to unravel what happens in the first hours of a star exploding.
For instance, SN 2012aw is what's known as a Type II supernova, the result of a very massive star's core collapsing.
According to Munari, astronomers "could take this opportunity to investigate how the initial shock propagated within the stellar structure" during the resulting explosion.
Clear Views, Despite "Mars Pollution"
It's fairly surprising the pre-supernova images even exist, Munari added.
Mars is currently half a degree from M95 in the night sky, and from our vantage point the planet is a hundred thousand times as bright as the whole galaxy.
That means light pollution from Mars would have made M95 a less attractive target for many stargazers, Munari said, and "most observers [likely] turned their attention away from M95, waiting for Mars to move a greater distance away."
But some night-sky photographers, including Parijat Singh of Arizona, persisted in keeping their telescopes trained on M95. (See more galaxy pictures.)
"I didn't realize Mars would contaminate my images," said Singh, who had picked the galaxy almost at random. (See pictures of the galaxy being partly obscured by light from Mars.)
Not until taking nearly an hour's worth of M95 images, pre-supernova, did Singh realize that Mars was messing with his shots. In the end, though, the pictures came out clear enough to see the galaxy.
"It was lucky," the National Institute of Astrophysics' Munari said.