Saturday, June 8, 2013
As many as one in five of the most energetic objects of the early universe were black holes—those fascinating deep space vacuum cleaners whose gravity is so immense that even light can’t escape.
An astronomical team that included University of Hawai`i’s Guenther Hasinger reported in The Astrophysical Journal that black holes formed early and often in the young universe.
(Image: Background radiation from when the universe was only a few hundred years old can provide hints of its structure. More detail on hthis image is here. Credits: Illustration by Karen Teramura, UHIfA. Credits for inserted images: cosmic microwave background (left): NASA WMAP Science Team; black hole blow up, AGN (center, top): NASA/JPL-Caltech; first stars blow up (center, bottom): NASA/JPL-Caltech, A. Kashlinsky (GSFC); Hubble Ultra Deep Field (right): NASA/ESA, S. Beckwith(STScI) and the HUDF Team.)
Hasinger, the Director of the university’s Institute for Astronomy, was part of a team that compared background infrared and x-ray signals dating back to the early universe. They used two NASA observatories, the Chandra X-ray Observatory and Spitzer Space Telescope
By comparing the results of the x-ray and infrared, they were able to determine that there were fluctuations in energy that were consistent in both forms of radiation, and that there was information in those fluctuations.
"This measurement took us some five years to complete and the results came as a great surprise to us," said Nico Cappelluti, an astronomer with the National Institute of Astrophysics in Bologna, Italy, and the University of Maryland, Baltimore County, in Baltimore.
In complex calculations, the scientists removed from the data the known star and galaxy sources of energy, and were left with a remainder they could study. And since black holes are particularly intense, energetic energy sources, the astronomers believed they could identify black hole signatures in the remnant radiation maps.
"Our results indicate black holes are responsible for at least 20 percent of the cosmic infrared background, which indicates intense activity from black holes feeding on gas during the epoch of the first stars," said Alexander Kashlinsky, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
All of that leads us into a detour into the insane world of black holes.
The density of the interior of black holes is so immense that nothing gets out. But like a stealthy beast that only makes a lot of noise when it’s eating, black holes are detectable because of the big energy signature of matter being sucked into them.
Around many black holes are accretion disks, where matter is being sucked toward oblivion. And where this final sucking occurs is called the “event horizon.” The matter spinning toward the event horizon lights up and sends out a kind of final radiation distress signal before it is gone. Like a cry of help from someone being drawn into a whirlpool.
Today, there are not nearly as many black hole signatures as there were in the early universe. Hasinger said that many of the universe’s black holes have gone silent. They have sucked all the matter in their regions of space, so there’s nothing left to eat—no accretion disks, so no radiation.
“Today only about 1% of all of these black holes are actively eating and radiating, while in the early universe probably all of them were active,” Hasinger said.
Today, astronomical research indicates every galaxy has a supermassive black hole at its center, and the larger galaxies have larger supermassive black holes. Supermassive black holes have masses ranging from a million to several billion solar masses.
For more information, visit: http://www.ifa.hawaii.edu/info/press-releases/blackholes2013/
© Jan TenBruggencate 2013