Super Bursts Located

Mapping energy bursts near a black hole has now become possible thanks to the computer and setting up plenty of radio antennas around the world. This is a pretty nifty achievement and the one thing that would make it better would be if we could do the same on the moon. That would give us a huge base line and a wonderful computation problem to handle the time lag.

This is still a pretty wonderful result. We have a burst associated with the black hole or better described, the event horizon. It consists of gamma rays, but as this burst passes through the surrounding dust we have a major radio signal develop as a secondary effect. The point is that they are in order and related.

Five years ago similar work was able to associate cosmic ray production with the remnants of super novas. At least it explains how it is possible for cosmic rays to have such high velocities. That it may be only from such events seems unlikely.

Super-energetic Bursts Discovered Near Giant Black Hole

ScienceDaily (July 4, 2009) — Using a worldwide combination of diverse telescopes, astronomers have discovered that a giant galaxy's bursts of very high energy gamma rays are coming from a region very close to the supermassive black hole at its core. The discovery provides important new information about the mysterious workings of the powerful "engines" in the centers of innumerable galaxies throughout the Universe.

The galaxy M87, 50 million light-years from Earth, harbors at its center a black hole more than six billion times more massive than the Sun. Black holes are concentrations of matter so dense that not even light can escape their gravitational pull. The black hole is believed to draw material from its surroundings -- material that, as it falls toward the black hole, forms a tightly-rotating disk.

Processes near this "accretion disk," powered by the immense gravitational energy of the black hole, propel energetic material outward for thousands of light-years. This produces the "jets" seen emerging from many galaxies. In 1998, astronomers found that M87 also was emitting flares of gamma rays a trillion times more energetic than visible light.

However, the telescopes that discovered these bursts of very high energy gamma rays could not determine exactly where in the galaxy they originated. In 2007 and 2008, the astronomers using these gamma-ray telescopes combined forces with a team using the National Science Foundation's continent-wide Very Long Baseline Array (VLBA), a radio telescope with extremely high resolving power, or ability to see fine detail.

"Combining the gamma-ray observations with the supersharp radio 'vision' of the VLBA allowed us to see that the gamma rays are coming from a region very near the black hole itself," said Craig Walker, of the National Radio Astronomy Observatory (NRAO).

"Pinning down this location addresses what was an open question and provides important clues for understanding how such highly energetic emissions are produced in the jets of active galaxies," said Matthias Beilicke, of Washington University in St. Louis, MO.

The gamma-ray flares from the galaxy were monitored by systems of large telescopes designed to detect faint flashes of blue light that result when gamma rays enter the Earth's atmosphere. Data from sensitive cameras in these systems can allow astronomers to infer the energy of the gamma rays and the direction from which they came. Their directional information, however, is not precise enough to narrow down the gamma-ray-emitting region within the galaxy.

The VLBA offered a million fold improvement in resolving power, allowing the scientists to determine that the gamma rays are coming from the immediate vicinity of the black hole. Though gamma rays are the most energetic form of electromagnetic radiation and radio waves the least energetic, both often arise from the same regions. This was shown clearly when M87's most energetic gamma-ray flares were accompanied by the largest flare of radio waves seen from that galaxy by the VLBA.

The radio flare began at about the time of the gamma-ray flares, but continued to increase in brightness for at least two months. "This tells us that energetic material burst out very close to the black hole, causing the gamma rays to be emitted and the radio flare to begin. As that material traveled down the jet, expanding and losing energy, the gamma-ray emission ceased, but the radio continued to increase in brightness," Walker explained.

"The VLBA showed us with great precision where the radio emission came from, so we know the gamma rays came from closer in toward the black hole," he added.

M87 is the largest galaxy in the Virgo Cluster of galaxies, at the center of a supercluster of galaxies that includes the Local Group, of which our own Milky Way is a member. The black hole in M87 has an "event horizon," from which matter cannot escape, roughly twice the size of our Solar System, or a tiny fraction of the size of the entire galaxy. The new measurements indicate that the gamma rays are coming from an area no larger than 50 times the size of the event horizon.

The telescope systems that detected the gamma-ray flares are the VERITAS array in Arizona, the H.E.S.S. system in Namibia, Africa, and the MAGIC system on La Palma in the Canary Islands.

The VLBA is a system of ten radio-telescope antennas stretching from Hawaii to the Caribbean, operated by the NRAO from Socorro, New Mexico. The VLBA offers resolving power equal to the ability to read a newspaper in New York while standing in Los Angeles.

Walker and Beilicke worked with Fred Davies of NRAO and New Mexico Tech, Henric Krawczynski of Washington University, Phil Hardee of the University of Alabama, Bill Junor of Los Alamos National Laboratory, Chun Ly of UCLA, and large research teams from VERITAS, H.E.S.S., and MAGIC. The scientists reported their findings in the July 2 online edition of the journal Science.

Possible Origin Of Cosmic Rays Revealed With Gamma Rays

ScienceDaily (Nov. 5, 2004) — An international team of astronomers has produced the first ever image of an astronomical object using high energy gamma rays, helping to solve a 100 year old mystery - an origin of cosmic rays. Their research, published in the Journal Nature on November 4th, was carried out using the High Energy Stereoscopic System (H.E.S.S.), an array of four telescopes, in Namibia, South-West Africa.

The astronomers studied the remnant of a supernova that exploded some 1,000 years ago, leaving behind an expanding shell of debris which, seen from the Earth, is twice the diameter of the Moon. The resulting image helps to solve a mystery that has been puzzling scientists for almost 100 years - the origin of cosmic rays. Cosmic rays are extremely energetic particles that continually bombard the Earth, thousands of them passing through our bodies every day. The production of gamma rays in this supernova shock wave tells us that it is acting like a giant particle accelerator in space, and thus a likely source of the cosmic rays in our galaxy.

Dr Paula Chadwick of the University of Durham said "This picture really is a big step forward for gamma-ray astronomy and the supernova remnant is a fascinating object. If you had gamma-ray eyes and were in the Southern Hemisphere, you could see a large, brightly glowing ring in the sky every night."

Professor Ian Halliday, CEO of PPARC which funds UK participation in H.E.S.S. said "These results provide the first unequivocal proof that supernovae are capable of producing large quantities of galactic cosmic rays - something we have long suspected, but never been able to confirm."

Gamma rays are the most penetrating form of radiation we know, around a billion times more energetic than the X-rays produced by a hospital X-ray machine. This makes it very difficult to use them to create an image - they just pass straight through any surface which we might use to reflect them, for instance. However, luckily for life on Earth, gamma rays from objects in outer space are stopped by the atmosphere; when this happens, a faint flash of blue light is produced, lasting for a few billionths of a second. The astronomers used images of these flashes of light, called Cherenkov radiation, to make a gamma ray 'image' for the first time.

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