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Scientists get first glimpse of black hole eating star, ejecting high-speed flare
- Date:
- November 27, 2015
- Source:
- Johns Hopkins University
- Summary:
- An
international team of astrophysicists 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.
This
artists impression shows a black hole consuming a star that has been
torn apart by the black hole's strong gravity. As a result of this
massive "meal" the black hole begins to launch a powerful jet that we
can detect with radio telescopes.
Credit: NASA/Goddard Space Flight Center/Swift
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 reported in the journal Science
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, said Sjoert van Velzen, a Hubble fellow at
Johns Hopkins.
"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."
Black holes are areas of
space so dense that irresistible gravitational force stops the escape of
matter, gas and even light, rendering them invisible and creating the
effect of a void in the fabric of space. 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, the
scientists said.
"Previous efforts to find evidence for these
jets, including my own, were late to the game," said van Velzen, who led
the analysis and coordinated the efforts of 13 other scientists in the
United States, the Netherlands, Great Britain and Australia.
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.
The
first observation of the star being destroyed was made by a team at the
Ohio State University, using an optical telescope in Hawaii. That team
announced its discovery on Twitter in early December 2014.
After
reading about the event, van Velzen contacted an astrophysics team led
by Rob Fender at the University of Oxford in Great Britain. That group
used radio telescopes to follow up as fast as possible. They were just
in time to catch the action.
By the time it was done, the
international team had data from satellites and ground-based telescopes
that gathered 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 in
hopes of tracking a jet emerging after the destruction of a star. This
galaxy is about 300 million light years away, while the others were at
least three times farther away. One light year is 5.88 trillion miles.
The
first step for the international team 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."
Van Velzen last year completed his doctoral dissertation
at Radboud University in the Netherlands, where he studied jets from
supermassive black holes. In the last line of the dissertation, he
expressed his hope to discover these events within four years. It turned
out to take only a few months after the ceremony for his dissertation
defense.
Van Velzen and his team were not the only ones to hunt
for radio signals from this particular unlucky star. A group at Harvard
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."
Story Source:
The above post is reprinted from
materials provided by
Johns Hopkins University.
Note: Materials may be edited for content and length.
Journal Reference:
S.
van Velzen, G. E. Anderson, N. C. Stone, M. Fraser, T. Wevers, B. D.
Metzger, P. G. Jonker, A. J. van der Horst, T. D. Staley, A. J. Mendez,
J. C. A. Miller-Jones, S. T. Hodgkin, H. C. Campbell, R. P. Fender.
A radio jet from the optical and X-ray bright stellar tidal disruption flare ASASSN-14li.
Science, 2015; DOI:
10.1126/science.aad1182
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