Quenching (astronomy)
In astronomy, quenching is a process in which a galaxy loses cold gas, thus strongly suppressing star formation. Evidence suggests that active supermassive black holes drive the process.
One common evolutionary path on the galaxy color–magnitude diagram may start with a blue spiral galaxy with lots of star formation. The black hole at its center may start growing rapidly, and somehow start quenching the galaxy, which relatively quickly transitions thru the "green valley", ending up more red.
