Galaxy Arp 220, located 250 million light-years from Earth, is home to seven different supernova explosions all going on at the same time. We've never seen so many stars exploding simultaneously in the same galaxy.

A team of astronomers at Chalmers and Onsala Space Observatory found that all seven supernovas went off in the last sixty years (allowing for the 250 million years for the light to reach Earth, of course). In cosmic terms, that's pretty much no time at all, as European Southern Observatory astronomer Rodrigo Parra explains:

"In Arp 220, we see far more supernovae than in our galaxy. We estimate that a star explodes in Arp 220 once every quarter [century]. In the Milky Way, there is only one supernova per century."

The astronomers believe it's proof that Arp 220 is one of the most efficient galaxies in the universe when it comes to making stars...and, ultimately, blowing them up. There's so many stars that have formed in that galaxy that there's always plenty of potential supernovas, even allowing for the fact that exactly when each star explodes in its own lifetime can vary by a whole lot more than sixty years. Team member John Conway adds:

"Arp 220 is well-known as a place where star formation is very efficient. Now we have been able to show that star factories like this are also supernova factories.

Via arXiv. Image by NASA, ESA, Hubble Heritage Team, Chalmers.

In a faraway galaxy, seven supernovas explode all at once