Strangulation causes galactic death: Study

London: British astronomers have found out the answer to an astronomical mystery as to how galaxies die. Evidence shows that they are ‘strangled to death’, which occurs after galaxies are cut off from the raw materials needed to make new stars. There are two types of galaxies in the Universe; roughly half are ‘alive’ which produce stars, while the other half are ‘dead’ ones which don't.

Alive galaxies such as the Milky Way are rich in the cold gas, mostly hydrogen, needed to produce new stars, while dead galaxies have very low supplies. Researchers have found that levels of metals contained in dead galaxies provide key ‘fingerprints’, making it possible to determine the cause of death.

If galaxies are killed by outflows suddenly pulling the cold gas out of the galaxies, then the metal content of a dead galaxy should be the same as just before it died, as star formation would abruptly stop. In the case of death by strangulation however, the metal content of the galaxy would keep rising and eventually stop, as star formation could continue until the existing cold gas gets completely used up.

The researchers were then able to independently test their results by looking at the stellar age difference between star-forming and dead galaxies. They said the conclusion is in agreement with the time it would take for a star-forming galaxy to be strangled to death as well.