Submission + - Galaxies Die by Slow 'Strangulation'
Astronomer Andrea Cattaneo from the Observatoire de Paris compares this tell-tale evidence to the high levels of carbon dioxide seen in a strangled human body. "During [strangulation], the victim uses up oxygen in the lungs but keeps producing carbon dioxide, which remains trapped in the body," wrote Dr Cattaneo. "Instead of building up CO2, the strangled galaxies accumulate metals — elements heavier than helium — produced by massive stars." On average, living, star-forming galaxies were four billion years younger than the dead ones. This matches the amount of time that the astronomers calculate would be needed for the galaxies to burn up their remaining gas supply during the strangulation. "This is the first conclusive evidence that galaxies are being strangled to death," says Peng. "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."