Stars suffer, too, you know. Astronomers have recently discovered a distinctive X-ray signal coming from a star on the verge of being engulfed by a black hole in a distant galaxy.
“This tell-tale signal, called a quasi-periodic oscillation or QPO, is a characteristic feature of the accretion disks that often surround the most compact objects in the universe — white dwarf stars, neutron stars and black holes. QPOs have been seen in many stellar-mass black holes, and there is tantalizing evidence for them in a few black holes that may have middleweight masses between 100 and 100,000 times the sun’s.”, said Rubens Reis, an Einstein Postdoctoral Fellow at the University of Michigan in Ann Arbor.
QPO stands for quasi-periodic oscillation, and it is basically the manner in which the X-ray light from an astronomical object flickers about certain frequencies. Until now, QPO had only been detected from a supermassive black hole – the largest type of black hole in a galaxy, on the order of hundreds of thousands to billions of solar masses.
“This discovery extends our reach to the innermost edge of a black hole located billions of light-years away, which is really amazing. This gives us an opportunity to explore the nature of black holes and test Einstein’s relativity at a time when the universe was very different than it is today”, added Reis.
“As hot gas in the innermost disk spirals toward a black hole, it reaches a point astronomers refer to as the innermost stable circular orbit (ISCO). Any closer to the black hole and gas rapidly plunges into the event horizon, the point of no return. The inward spiraling gas tends to pile up around the ISCO, where it becomes tremendously heated and radiates a flood of X-rays. The brightness of these X-rays varies in a pattern that repeats at a nearly regular interval, creating the QPO signal.”, he added.