The Whirlpool galaxy, M51, is merging with its smaller neighbor, NGC 5195. It’s expected that mergers like this will cause the black holes at the center to become active, but both black holes are much quieter than anticipated. (NASA, ESA AND THE HUBBLE HERITAGE TEAM (STSCI / AURA))

This Massive Black Hole Is Mysteriously Quiet, And Astronomers Don’t Know Why

Galactic mergers should push gas and dust into the centers of galaxies. So why are these two so quiet?

Scientists have studied the closest, largest, brightest galaxies to Earth for centuries.

Located close to the edge of the handle of the Big Dipper, the Whirlpool galaxy, M51, is a classic example of a close, bright, nearby spiral galaxy. (JEAN-DANIEL PAUGET / FLICKR)

Messier 51, the Whirlpool Galaxy, is one of astronomy’s most spectacular objects.

This sketch from the mid-1840s is the first ever one to reveal the spiral structure of any nebula in the night sky. Now known to be a spiral galaxy, Messier 51, the Whirlpool Galaxy, is one of the most well-studied galaxies beyond our Milky Way. (WILLIAM PARSONS, 3RD EARL OF ROSSE (LORD ROSSE))

This enormous, face-on galaxy was the first one ever to reveal its spiral structure.

Modern observations can reveal gas, dust, and stars in the optical, ultraviolet, and near-infrared from most observatories on Earth. Both M51 and its companion display fascinating extended properties. (ADAM BLOCK / MOUNT LEMMON SKYCENTER / UNIVERSITY OF ARIZONA)

The small object alongside it, the galaxy NGC 5195, is interacting and merging with the Whirlpool galaxy.

This ultraviolet image of Messier 51, taken by GALEX, reveals the hottest, youngest, most newly-formed stars found in the merging system of the Whirlpool galaxy and its smaller companion. Note how the gas-rich spiral galaxy forms new stars, but the gas-poor companion does not.(NASA / JPL-CALTECH / GALEX)