January 8, 2013
NASA Says Origin Of Gamma Ray Flare Is Far From Their Galaxy’s Black Hole
redOrbit Staff & Wire Reports - Your Universe Online
The source of a gamma ray flare that shot past Earth throughout much of 2011 has been discovered, and contrary to popular theory, they did not occur close to their galaxy´s central black hole, NASA officials announced on Monday.
Using data collected by both the Fermi Gamma-ray Space Telescope and the National Science Foundation's Very Long Baseline Array (VLBA), astronomers at the U.S. space agency have discovered that the energy blasts originated from a galaxy known as 4C +71.07, and that the emission originated approximately 70 light-years away from that galaxy´s central black hole.
That contradicts what some experts have postulated — that gamma-ray outbursts only occur “in close proximity to a galaxy's central black hole, the powerhouse ultimately responsible for the activity,” NASA officials said in a statement.
However, a few rare observations — such as in this instance — suggest that this might not always be the case.
The source galaxy, 4C +71.07, is located in the constellation Ursa Major and was first discovered in the 1960s because it was a source of strong radio emissions. Approximately three decades later, NASA's Compton Gamma-Ray Observatory (CGRO) detected high energy flares but remained quiet during the first 30 months or so of Fermi´s time in orbit.
That changed in November 2011, however, when during the high point of the outburst, the galaxy “was more than 10,000 times brighter than the combined luminosity of all of the stars in our Milky Way galaxy.”
"This renewed activity came after a long slumber, and that's important because it allows us to explicitly link the gamma-ray flares to the rising emission observed by radio telescopes," said David Thompson, a Fermi deputy project scientist at NASA's Goddard Space Flight Center.
Light from 4C +71.07 takes roughly 10.6 billion years to reach Earth, which means that astronomers observing the galaxy are seeing it as it existed when the universe was less than a quarter of its current age, NASA explained. The supersized black hole at its core weighs 2.6 billion times the mass of our sun.
“Some of the matter falling toward the black hole becomes accelerated outward at almost the speed of light, creating dual particle jets blasting in opposite directions. One jet happens to point almost directly toward Earth,” the American space agency said. “This characteristic makes 4C +71.07 a blazar, a classification that includes some of the brightest gamma-ray sources in the sky.”
During the autumn of 2011, VLBA images “revealed a bright knot that appeared to move outward at a speed 20 times faster than light,” they continued. That knot “passed through a bright stationary feature of the jet” on April 9, and the blazer become brighter “at visible wavelengths in step with the higher-energy emission.”
“During the most intense period of flaring, from October 2011 to January 2012 “¦ scientists found the polarization direction of the blazar's visible light rotated in the same manner as radio emissions from the knot. They concluded the knot was responsible for the visible and the gamma-ray light, which varied in sync,” the NASA representatives concluded. “This association allowed the researchers to pinpoint the location of the gamma-ray outburst to about 70 light-years from the black hole.”