Astronomers have found a galaxy that represents a new type, and falls within the range of active galaxies known as Seyfert galaxies. It glows green because of X-rays spewing from a gigantic black hole at its center that weighs several million to billion times more than the sun. Dubbed a “green bean” galaxy, it appears to be quite rare. Scientists found only about 20 green beans in the vast swath of sky surveyed for this research.

These galaxies will provide a window into the evolution of quasars, which are faraway galaxies powered by massive black holes. “These things are light echoes,” said Mischa Schirmer, the lead researcher of a paper reporting the findings in the Astrophysical Journal. “What we see is a quasar that is shutting down,” Schirmer said. “It hasn’t shut down entirely yet.”