In news seemingly plucked from a TMZ headline, a team of scientists from the United States and Canada is reporting that a trio of rejected former superstars have self-destructed in relative obscurity.
More specifically, at a conference at North Carolina State University on Friday, the team presented images captured by the Hubble Space Telescope that confirm three supernovas that had previously been flung from their home galaxies millions, possibly billions, of years ago exploded in vast empty solitude, hundreds of light-years away from the nearest galaxy.
While most supernovas are found inside galaxies containing hundreds of billions of stars, the three supernovas studied by the team were found between galaxies within three large clusters of several thousand galaxies each.
The team was led by Melissa Graham, a post-doctoral fellow at the University of California at Berkeley, and included David Sand of Texas Tech University, Dennis Zaritsky of the University of Arizona, and Chris Pritchet of the University of Victoria. Their findings are contained in a paper that has been accepted for publication by the Astrophysical Journal.
So-called hostless supernovas provide rare insight into what exists in the empty spaces between galaxies and can help astronomers understand how galaxy clusters formed and evolved throughout the history of the universe, according to the team.
The three isolated supernovas were initially detected between 2008 and 2010 by the Multi-Epoch Nearby Cluster Survey using the Canada-France-Hawaii Telescope on Mauna Kea. Astronomers at the time were unable to rule out the possibility that the supernovas were hosted by a galaxy too faint to be detected. However, the images collected by the Hubble Telescope were about 10 times sharper and thus able to conclusively confirm that the supernovas exploded in empty space.
Stars and supernovas typically exist within galaxies. However, galaxies within massive clusters experience gravitational forces that separate off about 15 percent of their stars. So massive are these clusters that the displaced stars remain gravitationally bound within empty regions between clusters.
The displaced stars are typically too faint to be detected — unless they explode as supernovas, as the three included in the study had.
"We have provided the best evidence yet that intracluster stars truly do explode as Type 1a supernovae and confirmed that hostless supernovae can be used to trace the population of intracluster stars, which is important for extending this technique to more distant clusters," Graham said in a release issued Thursday.
A Type 1a supernova occurs within a binary system in which a white dwarf star and another star orbit each other.