黑洞的星系塑造能力

Data from a now-defunct X-ray satellite is providing new insights into the complex tug-of-war between galaxies, the hot plasma that surrounds them, and the giant black holes that lurk in their centres. Launched from Japan on February 17, 2016, the Japanese space agency (JAXA) Hitomi X-ray Observatory functioned for just over a month before contact was lost and the craft disintegrated. But the data obtained during those few weeks was enough to paint a startling new picture of the dynamic forces at work within galaxies.

New research, published in the journal Nature today, reveals data that shows just how important the giant black holes in galactic centres are to the evolution of the galaxies as a whole.

"We think that supermassive black holes act like thermostats," said Brian McNamara, University Research Chair in Astrophysics at the University of Waterloo. "They regulate the growth of galaxies." 

Champagne bubbles of plasma

During its brief life, the Hitomi satellite collected X-ray data from the core of the Perseus cluster, an enormous gravitationally-bound grouping of hundreds of galaxies. Located some 240 million light years from earth, the Perseus cluster is one of the largest known structures in the universe. The cluster includes not only the ordinary matter that makes up the galaxies, but an "atmosphere" of hot plasma with a temperature of tens of millions of degrees, as well as a halo of invisible dark matter. 

Earlier studies, going back to the 1960s, have shown that each of the galaxies in the cluster - and indeed most galaxies - likely contains a supermassive black hole in its centre, an object 100 million to more than ten billion times as massive as our sun. 

"These giant black holes are among the universe's most efficient energy generators, a hundred times more efficient than a nuclear reactor," said McNamara from Waterloo's Department of Physics and Astronomy in the Faculty of Science. "Matter falling into the black hole is ripped apart, releasing vast amounts of energy in the form of high speed particles and thermal energy."