Three stellar exiles exploded in solitude hundreds of light-years away from their closest cosmic neighbors, it was revealed this week.
Supernova -- giant exploding stars at the end of their lives -- are usually embedded within galaxies that play host to billions of stars. But new data from the Hubble Space Telescope confirms that three stars went supernova alone, in the void between galaxies in different clusters.
These huge star explosions could give scientists a better idea of what happens in those mysterious, empty areas of space between galaxies.
The three errant supernova were first discovered between 2008 and 2010 by using a telescope on Mauna Kea in Hawaii. But the Hubble's more recent, sharper observations revealed more about the three supernova.
The earlier survey couldn't rule out the possibility that the supernova were embedded in faint galaxies, but the newer Hubble images did -- showing that they truly are exiles.
The supernovas were all about 300 light years from their closest galactic neighbors, "nearly 100 times farther than our sun’s nearest stellar neighbor, Proxima Centauri, 4.24 light years distant," wrote Robert Sanders of the University of California, Berkeley in a statement.
Each of the supernovas came from clusters of galaxies that are about 1 billion light years from Earth.
Any planets orbiting these exploding stars likely would have been destroyed in the blast, according to Melissa Graham, a Berkeley researcher and lead author of a new study about the supernovas. But before those planets were destroyed, they probably had an interesting view of the night sky.
Inhabitants of those worlds, if any existed, would have looked up into a black night sky without bright stars.
“It would have been a fairly dark background indeed, populated only by the occasional faint and fuzzy blobs of the nearest and brightest cluster galaxies," Graham said in a statement. The new study is accepted for publication in the Astrophysical Journal.
While these supernovas may have exploded into the void, they are probably not the only stars stuck in between galaxies. A recent study suggests that about 15% of stars in massive clusters of galaxies are expelled into intergalactic space -- thanks to the same forces that exiled the three supernovas.
The three stars observed for this study likely exploded as Type Ia supernova, a type of stellar explosion that scientists think occurs when a smaller star orbiting a larger one disintegrates as its material feeds the larger star. In other words, the exploding stars may have had companions in the void.
“The companion was either a lower-mass white dwarf that eventually got too close and was tragically fragmented into a ring that was cannibalized by the primary star, or a regular star from which the primary white dwarf star stole sips of gas from its outer layers," Graham said. "Either way, this transfer of material caused the primary to become unstably massive and explode as a Type Ia supernova.”
Graham and her team also found another supernova, but they aren't sure if it's an exile. That supernova could be embedded in a relatively small galaxy or even a globular cluster, a collection of less than 1 million stars.
If the fourth supernova is inside a globular cluster, it would mark the first time a supernova has been seen exploding inside a cluster like that, the Berkeley statement said.