Back when Earth's continents were mushed together into a single blob called Pangaea and reptiles were just beginning to overtake amphibians as the dominant life-forms on Earth, a star strayed too close to a black hole. If they can understand how and why these changes occur in stellar-mass black holes over a period of weeks, scientists could shed light on how supermassive black holes evolve over millions of years and how they affect the galaxies in which they reside. And on November 22, 2014, the X-rays from that dying star landed in ASASSN's eye, and the instrument sent data about them down to scientists on Earth.
Astronomers from Massachusetts Institute of Technology (MIT) have detected X-ray pulses originating from an area very close to a black hole's event horizon, and they believe the source of this pulse could be a white dwarf. They found what they were looking for in data from two x-ray space telescopes.More news: Unai Emery says Arsenal can't make permanent signings this month
Because MAXI had caught the black hole's initial outburst, the team began studying the X-rays emitted from the black hole over a month, measuring how they bounced off the accretion disk.
The researchers think the bits of leftover star providing energy pulses circle around the innermost stable circular orbit (ISCO) of the black hole - the last point of safety before destruction. They apparently detected "echoes" within the explosion of X-ray light that helped them discover what happens to the black hole itself during an outburst. That data, along with the black hole's mass, suggests the supermassive black hole at the centre of the event labelled ASASSN-14li is spinning at 50 percent the speed of light. That is the smallest orbit that a particle can safely travel around the black hole. Waves of X-rays formed "light echoes" that reflected off the swirling gas near the black hole and revealed changes in the environment's size and shape.More news: Samsung goes big with a 219-inch TV
"That's not super fast - there are other black holes with spins estimated to be near 99 percent the speed of light", said Dheeraj Pasham, a postdoctoral fellow at MIT and lead author of the paper, in a media release. While fairly common in the universe (there is one dormant giant at the center of the Milky Way), black holes remain a mystery. With only a couple dozen examples it would be premature to make big-picture conclusions (especially if we're not interpreting the data correctly), but the pattern might indicate that supermassive black holes grow primarily by prolonged feeding from accretion disks, which would spin the black holes up like water from a hose hitting a basketball. They followed the signal that they said pulsed every 131 seconds and persisted for at least 450 days. He made a decision to apply his code to the three datasets for ASASSN-14li, to see if any common periodic patterns would rise to the surface. According to their calculations, the black hole is rotating at almost half the speed of light. Alone, it would not have been enough to emit any sort of detectable radiation. As the white dwarf came in contact with this hot stellar material, it likely dragged it along as a luminous overcoat of sorts, illuminating the white dwarf in an intense amount of X-rays each time it circled the black hole, every 131 seconds. A relatively low rotation rate would implicate mergers as the primary factor, because these random smashups likely wouldn't keep spinning the growing black hole up in the same direction.
As the black hole strips away the star, this volatile matter heats up to 1 million degrees Celsius as it gets pulled into a disk around the black hole, explained Pasham. "But at least in terms of the properties of the system, this scenario seems to work".More news: Knicks and Kings reportedly talking Enes Kanter-Zach Randolph trade
So, how fast was the black hole spinning? He hopes that when the European Athena X-ray mission launches in 2031, it will find many more and really break open this line of investigation.