科学美国人60秒:Frenzy-Feeding Black Hole Makes Galaxy Most Luminous

Astronomers have discovered the most luminous galaxy ever found, shining with the equivalence of 300 trillion suns from the far side of the visible universe. But almost all of that light is being produced by the galaxy’s central supermassive black hole—not by its stars. The enlightening finding is in The Astrophysical Journal. [Chao-Wei Tsai et al, The Most Luminous Galaxies Discovered by WISE]

Black holes are black because light itself cannot escape once falling in. But a feeding black hole is surrounded by a whirling, white-hot disk of glowing debris—material heated to millions of degrees as it spirals down to oblivion. The black hole in this faraway galaxy is on a feeding frenzy. The activity produces enough light to warm up most of the galaxy’s dust—which gives the whole galaxy an infrared glow that we can detect from more than 12.5 billion light-years away.

Considering we are seeing this giant black hole’s activity from a time when the universe was only a tenth of its present age, astronomers are puzzled about how it could’ve grown so big so fast. A young, hungry black hole usually takes an occasional break from feeding—its glowing debris disk can get so intense it pushes incoming material further away. Think of a baby burping mid-meal.  

But this particular galaxy’s black hole seems to have circumvented this limitation—if it’s burping, the burps seem to be few and far between.  

One theory is that it must be spinning very slowly—the slower a black hole spins, the weaker its repulsive burps may be, and the longer it can gorge uninterrupted. study co-author Andrew Blain of the University of Leicester says that a slow spin may be how this black hole has sustained its binge, which he calls the equivalent of “winning a hot-dog-eating contest lasting hundreds of millions of years.” And if there’s any mustard with those dogs, rest assured: it’s hot.

—Lee Billings