How a Black Hole's Corona Stretched Out in an Hour ✎ express
The XMM-Newton X-ray telescope stared at galaxy Mrk 1044 for two straight hours. Inside it, a black hole is surrounded by a swirling disk of superheated gas. This gas glows in X-rays, and its light flickers — brighter, then dimmer.
For the first half hour, the flickering of soft and hard X-rays was in step. Then the hard glow started lagging behind the soft, like an echo. Meanwhile, the overall brightness barely changed. The lag was so strong that on a plot of brightness versus hardness, it traced a loop shaped like the letter O.
The lag appeared suddenly, within one hour of observations. That means the corona stretched out quickly. Two more clues confirm this: the emission became smoother, and the iron line in the spectrum became narrower and weaker. Such rapid restructuring of the corona is a new twist in astrophysics.
An hour later, the corona might have contracted again: we didn't see that. But now it's clear: we need to look at short time intervals, not just average plots. A black hole changes faster than we thought.
The loop on the brightness–hardness plot resembles the one traced by body temperature during a fever: first a rise, then a fall, and on the graph, a closed curve.
In Interstellar, the spacecraft flies through the accretion disk: that same glowing corona, except in the movie it's static, while in reality it breathes and changes within minutes.