Galactic annihilation recipe finally disclosed.
Astronomers classify galaxies as "alive" if they are actively forming new stars. Galaxies lacking new stellar populations are called "red-and-dead." Molecular gas reserves are key to forming new stars within galaxies, and if a galaxy possesses no new stars, it must be gas-free. Gas can be removed by intense star-formation periods, mergers, and interactions. Rapid journeys through a galaxy cluster's intergalactic medium also strip interior gas away. The first red-and-dead galaxy in our cosmic backyard was identified in 2018: NGC 1277, which hasn't formed new stars in approximately 10 billion years.