Galaxies tend to herald their death far in advance with the telltale sign coming when they are done producing new stars.
According to BBC News, what comes next is a slow death in which all the materials produced during the stars' formation actually "suffocates" the galaxy. Researchers from the University of Cambridge and the Institute for Astronomy, Royal Observatory published their study in the journal Nature.
"Metals are a powerful tracer of the history of star formation: the more stars that are formed by a galaxy, the more metal content you'll see," study lead author Yingjie Peng, of Cambridge's Cavendish Laboratory and Kavli Institute of Cosmology, said in a press release. "So looking at levels of metals in dead galaxies should be able to tell us how they died."
For their study, the researchers examined a number of galaxies - both alive and dead.
"This is the first conclusive evidence that galaxies are being strangled to death," Peng said. "What's next though, is figuring out what's causing it. In essence, we know the cause of death, but we don't yet know who the murderer is, although there are a few suspects."
Quick deaths tended to be more violent and would occur when the galaxy lost its supply of gas and its levels of metals remained static. But if a galaxy continued to build up metals after its source of gas, and therefore its means of creating stars, was gone, the death would be slow and deliberate.
"We found that for a given stellar mass, the metal content of a dead galaxy is significantly higher than a star-forming galaxy of similar mass," study co-author Roberto Maiolino said in the release. "This isn't what we'd expect to see in the case of sudden gas removal, but it is consistent with the strangulation scenario."
