Tag Archive: Supermassive black hole


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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:

  1. 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

By Agence France-Presse
A composite of the giant barred spiral galaxy NGC 6872, obtained from NASA on January 10, 2013. (AFP)

Astronomers on Friday said they had observed the largest structure yet seen in the cosmos, a cluster of galaxies from the early Universe that spans an astonishing four billion light years.

The sprawling structure is known as a large quasar group (LQG), in which quasars — the nuclei of ancient galaxies, powered by supermassive black holes — clump together.

The discovery in the deep Universe was made by a team led by Roger Clowes at the Jeremiah Horrocks Institute at Britain’s University of Central Lancashire.

 

Read Full Article Here

Space

The Milky Way’s Black Hole Shoots Out Brightest Flare Ever

by Nancy Atkinson on November 7, 2012

 universetoday

This false-color image shows the central region of our Milky Way Galaxy as seen by Chandra. The bright, point-like source at the center of the image was produced by a huge X-ray flare that occurred in the vicinity of the supermassive black hole at the center of our galaxy.
Image: NASA/MIT/F. Baganoff et al.

For some unknown reason, the black hole at the center of the Milky Way galaxy shoots out an X-ray flare about once a day. These flares last a few hours with the brightness ranging from a few times to nearly one hundred times that of the black hole’s regular output. But back in February 2012, astronomers using the Chandra X-Ray Observatory detected the brightest flare ever observed from the central black hole, also known as Sagittarius A*. The flare, recorded 26,000 light years away, was 150 times brighter than the black hole’s normal luminosity.

What causes these outbursts? Scientists aren’t sure. But Sagittarius A* doesn’t seem to be slowing down, even though as black holes age they should show a decrease in activity.

Mysterious X-ray flares caught by Chandra may be asteroids falling into the Milky Way’s giant black hole. Credit: X-ray: NASA/CXC/MIT/F. Baganoff et al.; Illustrations: NASA/CXC/M.Weis

 

Earlier this year, a group of researchers said that the outbursts may come from asteroids or even wandering planets that come too close to the black hole and they get consumed. Basically, the black hole is eating asteroids and then belching out X-ray gas.

Astronomers involved in this new observation seem to concur with that line of thinking.

Joanna Carver, reporter

20121105144514-0.jpg(Image: NASA/MIT/F. Baganoff et al.)

The black hole at the centre of our galaxy isn’t growing old gracefully. Every day or so this big beast belies its age by shooting off an X-ray flare that can outshine its usual output by more than a hundred times.

This image, taken in February by NASA’s orbiting Chandra X-Ray Observatory, shows the brightest such flare ever seen. It’s 150 times brighter than the usual luminosity of the black hole, known as Sagittarius A*. It’s not clear why these flares happen, but researcher Michael Nowak of the Massachusetts Institute of Technology, who led the study, suggests they may be the last gasps of asteroids being swallowed by the black hole.

“We’re learning what black holes do when they’re old,” says Joey Neilsen, another MIT astrophysicist who worked on the study. “They’re no young whippersnappers like quasars, but they’re still active, and how they’re active is an interesting question.”

The black hole itself isn’t really shining, since it’s such a powerful space-time-defying vacuum of everything that even light has no way out. It’s actually the stuff that it’s sucking down that’s rubbing against itself, emitting radiation before its inevitable destruction.

By the way, if you want to look into the face of dark inescapable obliteration, look skyward, between the Sagittarius and Scorpius constellations. You can’t see it, but it can see you.

Journal reference: The Astrophysical Journal, DOI: 10.1088/0004-637x/759/2/95