A black hole devouring a star. Credit: NASA
An international team of astrophysicists led by a Johns Hopkins University scientist has for the first time witnessed a star being swallowed by a black hole and ejecting a flare of matter moving at nearly the speed of light.
The finding tracks the star—about the size of our sun—as it shifts from its customary path, slips into the gravitational pull of a supermassive black hole and is sucked in. “These events are extremely rare,” van Velzen said. “It’s the first time we see everything from the stellar destruction followed by the launch of a conical outflow, also called a jet, and we watched it unfold over several months.”
Astrophysicists had predicted that when a black hole is force-fed a large amount of gas, in this case a whole star, then a fast-moving jet of plasma – elementary particles in a magnetic field – can escape from near the black hole rim, or “event horizon.” This study suggests this prediction was correct. Supermassive black holes, the largest of black holes, are believed to exist at the center of most massive galaxies. This particular one lies at the lighter end of the supermassive black hole spectrum, at only about a million times the mass of our sun, but still packing the force to gobble a star.
Artist’s conception of a star being drawn toward a black hole and destroyed (left), and the black hole later emitting a “jet” of plasma composed of the debris left from the star’s destruction. Modified from an original image by Amadeo Bachar.
The 1st observation of the star being destroyed was made by a team at the Ohio State University with an optical telescope in HI, Dec. 2014.
After reading about the event, van Velzen contacted an astrophysics team led by Rob Fender at the University of Oxford. They used radio telescopes and were just in time to catch the action with data from satellites and ground-based telescopes: X-ray, radio and optical signals, providing a stunning “multi-wavelength” portrait of this event.
It helped that the galaxy in question is closer to Earth than those studied previously ie 300 million light years away. The first step was to rule out the possibility that the light was from a pre-existing expansive swirling mass called an “accretion disk” that forms when a black hole is sucking in matter from space. That helped to confirm that the sudden increase of light from the galaxy was due to a newly trapped star.
“The destruction of a star by a black hole is beautifully complicated, and far from understood,” van Velzen said. “From our observations, we learn the streams of stellar debris can organize and make a jet rather quickly, which is valuable input for constructing a complete theory of these events.”
A group at Harvard also observed the same source with radio telescopes in New Mexico and announced its results online. Both teams presented results at a workshop in Jerusalem in early November. It was the first time the two competing teams had met face to face.
“The meeting was an intense, yet very productive exchange of ideas about this source,” van Velzen said. “We still get along very well; I actually went for a long hike near the Dead Sea with the leader of the competing group.”
http://hub.jhu.edu/2015/11/26/black-hole-eats-a-star http://phys.org/news/2015-11-scientists-glimpse-black-hole-star.htmljCp
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