Black Hole Too Big for its Breeches

A supermassive black hole in the early universe is at least 10 times too heavy for its host galaxy, raising questions about galaxy and black hole coevolution.

CID-947 is a supermassive black hole that’s visible across the observable universe because it’s actively gobbling down gas and spitting out radiation. It’s a classic quasar in every way except one: its supermassive black hole is too heavy for its galaxy.

Over the past decade, astronomers have discovered that supermassive black holes have a scaling relationship with their host galaxies: the more massive the black hole, the more massive the galaxy. On average, a supermassive black hole has a mass 1/100 to 1/1,000 times that of its host galaxy. Seemingly consistent relationships like this one have led astronomers to suspect that a black hole’s growth and its host galaxy’s growth are intertwined.

But CID-947 doesn’t lie anywhere near this relation. At 2 billion years after the Big Bang, this quasar only weighs eight times less than its host galaxy.

The Pleiades

The figure and the caption are from “A popular handbook and atlas of astronomy” by Sir William Peck (1862-1925), published in New York in 1891:

In various parts of the heavens stars are seen crowded together, forming what are called star clusters. Several of these objects can be distinctly seen with the unaided eye, but the greater number require the telescope to render them visible. The most conspicuous of the naked-eye groups, the well-known Pleaides, is situated in the constellation of Taurus. In this cluster, with ordinary eyesight only, six or seven stars can be seen, but with the telescope the number increases with the space-penetrating power, and with some instruments over 400 stars can be counted.