NASA's WISE mission captures black hole's wildly flaring jet

Posted by pt91 at Sep 21, 2011 11:10 AM |
University of Leicester academic involved in ‘unusual case of a serendipitous discovery’
NASA's WISE mission captures black hole's wildly flaring jet

Artist's illustration of flaring black hole. Image Credit: Poshak Gandhi, Japanese Space Agency; NASA

Issued by University of Leicester Press Office on 21 September 2011

Artist's illustration and animation of flaring black hole available below or via pt91@le.ac.uk

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Astronomers using data from NASA's Wide-field Infrared Survey Explorer (WISE) have captured rare data of a flaring black hole, revealing new details about these powerful objects and their blazing jets.

"Imagine what it would be like if our sun were to undergo sudden, random bursts, becoming three times brighter in a matter of hours, and then fading back again. That's the kind of fury we observed in this jet," said Poshak Gandhi with the Japanese Aerospace Exploration Agency in Japan, who is lead author of a new study on the results appearing in the Astrophysical Journal Letters.

"With WISE's infrared vision, we were able to zoom in on the inner regions near the base of the black hole's jet for the first time. We not only measured physical characteristics in unprecedented detail, but also watched how they changed on short timescales," he said.

It was a chance encounter between Poshak and Professor Andrew Blain, of the University of Leicester, that led to the findings. Professor Blain said: “As a WISE science team member, being involved in the project since it started in 2001, I had access to the data before the public data release was made,   and on a collaborative visit to the University of Nagoya, I happened to meet Poshak, who I had known from being the UK a decade ago. Poshak asked me about the performance of WISE for variable objects,  and I said that it visited patches of the sky every 90 minutes for a day, and then not again for six months.  That means that it is only sensitive to things that vary on timescales from hours to a day.

“Poshak said he had recently worked on a binary system that might vary on just those timescales, and  we looked through the images from the telescope and saw that it did. On returning to Leicester I carefully  measured the changes, and then we found we had the first observation, made at infrared wavelengths, for seeing quick changes taking  place in the high-energy particles being shot from the poles of the blackhole.

"No previous satellites observed  frequently enough at these wavelengths to catch the variation taking place.  Only a few other WISE-sampled objects show such dramatic changes, and it was just good luck that we  found that one after my talk.”

The black hole, called GX 339-4, was known before. It lies more than 20,000 light-years away near the center of our galaxy, and has a mass at least six times greater than that of our sun. Like other black holes, it is an ultra-dense collection of matter, with gravity that is so great even light cannot escape. In this case, the black hole, which probably formed from a star that exploded, is orbited by a companion star that feeds it. Most of the material from the companion star is pulled onto the black hole, but some of it is blasted away as a jet flowing at nearly the speed of light.

Professor Blain added: “Without the Leicester-Nagoya collaborative agreement being in place, and me going to Japan on the exchange program, I probably would not have met up with Poshak, and we would not have spotted this together.

“It is the first time that I've been involved in such an unusual case of a serendipitous discovery, and one which the relationship with Nagoya, built up on University of Leicester's expertise in specifically X-ray astronomy was crucial.

“It also took place directly after the Sendai earthquake in March, and I almost didn't take the trip!”

Scientists study jets to learn more about the extreme environments around black holes. They have learned a great deal about the material feeding black holes, called accretion disks, and about the jets themselves through studies using X-rays, gamma rays and radio waves. But key measurements of the brightest part of the jets, located at their bases, have been difficult despite decades of work. WISE is offering a new window into this missing link through its infrared observations.

"To see bright flaring activity from a black hole you need to be looking at the right place at the right time," said Peter Eisenhardt, the project scientist for WISE at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "WISE snapped sensitive infrared pictures every 11 seconds for a year, covering the whole sky, allowing it to catch this rare event." Observing the jet's variability was possible due to images taken of the same patch of sky over time -- a feature of NEOWISE, the asteroid-hunting portion of the WISE mission.

Poshak explained that WISE data allowed him and his team to zoom in on the very compact region around the base of the jet streaming out the black hole. "The size of the region we are probing is equivalent to the width of a dime seen at the distance of our sun," he said.

The results surprised the team, showing huge and erratic fluctuations in the jet activity on timescales ranging from 11 seconds to a few hours. This type of variability in jets has never been seen with this kind of precision before. WISE had not just one, but four infrared cameras, allowing astronomers to determine changes in infrared light in real time. The observations, which Poshak describes as a "dance of infrared colors," show that the size of the base of the jet is varying. Its radius was measured to be about 15,000 miles (25,000 kilometers) across, with dramatic changes as large as a factor of 10 or more.

"If you think of the black hole's jet as a firehose, then it's as if we've discovered the flow is intermittent and the hose itself is varying wildly in size," said Poshak.

The new data also allowed the astronomers to make the best measurements yet of the black hole's magnetic field, which is 30,000 times more powerful than that generated by our Earth at its surface. Such a strong field is required for accelerating and channeling the flow of matter into a narrow jet. The WISE data are bringing astronomers closer than ever to understanding how this exotic phenomenon works.

Poshak and his team plan to continue to use the WISE data, some of which went public last April 2011, to search for more flaring black holes.

Read the NASA press release on this story.

NOTES TO EDITORS:

JPL manages and operated WISE for NASA's Science Mission Directorate, Washington. The spacecraft was put into hibernation mode after it scanned the sky twice, completing its main objectives. The principal investigator, astronomer Edward Wright, is at UCLA. The mission was competitively selected under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory, Logan, Utah; and the spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

Other authors of the paper include: A.W. Blain of the University of Leicester, United Kingdom; D.M. Russell and S. Markoff of the University of Amsterdam; P. Casella of the University of Southampton, United Kingdom; J. Malzac of Université de Toulouse, France; S. Corbel of Université Paris Diderot and Commissariat à l'énergie atomique Saclay, France; P. D’Avanzo of Istituto Nazionale di Astrofisica, Italy; F.W. Lewis of University of Glamorgan, Wales; M. Cadolle Bel of the European Space Astronomy Centre, Spain; P. Goldoni of Laboratoire Astroparticule et Cosmologie, France; S. Wachter of the California Institute of Technology, Pasadena, Calif.; D. Khangulyan of the Japanese Aerospace Exploration Agency; and A. Mainzer of JPL.

For more information, visit:

http://www.nasa.gov/wise

-end-

For more information contact Professor Andrew Blain, University of Leicester Department of Physics and Astronomy

Email: ab520@le.ac.uk

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Image Credit: Poshak Gandhi, Japanese Space Agency; NASA

Caption:

Feeding a Flaring Black Hole: This artist's concept illustrates what the flaring black hole called GX 339-4 might look like. Infrared observations from NASA's Wide-field Infrared Survey Explorer (WISE) reveal the best information yet on the chaotic and extreme environments of this black hole's jets. GX 339-4 likely formed from a star that exploded. It is surrounded by an accretion disk (red) of material being pulled onto the black hole from a neighboring star (yellow orb). Some of this material is shot away in the form of jets (yellow flows above and below the disk). The region at the base of the jets glows brightly in infared light.

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