This One Distant, Red, Gas-Free Galaxy Defies Astronomers’ Expectations
“When two similarly-sized galaxies merge, it triggers a starburst: a massive formation of new stars. Under the right circumstances, some gas will form stars while the remainder is expelled, lost forever to the intergalactic medium. Once the gas for forming new stars is used up, the galaxy simply ages as the bluest, most massive stars die off. Over billions of years, only the redder, dimmer, lower mass stars remain.”
In astronomy, young galaxies actively form stars, and glow bright blue through the process. Only after many billions of years and at least one cataclysmic event do galaxies settle down into a gas-free, red state, once all the bluer stars have died out. “Red and dead” galaxies appear in the late Universe, normally as giant elliptical galaxies that lost their gas aeons ago.
Which is why this one galaxy is so puzzling: it’s red, dead, massive and compact, but it’s also sending us its light from 10.8 billion years ago!