New research helps explain powerful particle accelerators
A new study, based on data collected by NASA’s Fermi Gamma-ray telescope, suggests the universe's most powerful particle accelerators behave differently than previously thought. The study, published in the scientific journal Nature, shows that the bulk of gamma rays are produced much further away from black holes than scientists expected.
The Gamma-ray sky high above the Milky Way is dominated by active galactic nuclei (AGN), or so-called blazars. In the center of these galaxies are black holes whose mass is several hundred million times the size of the sun – some more than a billion times larger. When the black hole captures matter from their surroundings it releases energy that shoots out two jet rays where particles are accelerated to speeds very close to the speed of light.
“Blazars are the universe's largest accelerators, but we are still missing many pieces of the puzzle to understand how they work in detail," says Stefan Larsson, an astronomer at Stockholm University researching blazars using data from Fermi.
The Swedish Fermi consortium is led by scientists from Stockholm University's Department of Physics, together with the Royal Institute of Technology and the University of Kalmar.
“These results are a significant step forward in our understanding of these jets," says Roger Blandford at The Kavli Institute for Particle Astrophysics and Cosmology, where most of the data analysis was conducted.
The key to the new results was a combination of the highly sensitive observations made by the Fermi telescope which were made simultaneously with a number of telescopes around the world.
Previous observations of blazars have suggested that visible light is quite far from the black hole – around 1 light year away. Gamma rays, on the other hand, have been expected to occur around 100 to 200 times closer to the black hole. The new observations of blazars located in the Virgo constellation suggest, however, that gamma radiation and the visible light are produced in the same place. This seems to suggest gamma rays are generated much further away than previously thought.
Since the jets beams’ energy is mostly emitted in the form of gamma rays, scientists must now rethink previous theories and construct a model for jet rays which transport energy much farther away. This, according to the researchers behind the study, is a major challenge.
“The new results are one of several startling discoveries that Fermi made during the year and a half that the satellite collected the data. Fermi has really exceeded our expectations," says Jan Conrad, associate professor of physics at the Oskar Klein Center, Stockholm University and project manager for the Swedish universities participating in Fermi.
Related links:
Recent article in the New Scientist: http://www.newscientist.com/article/dn18608-universes-highenergy-haze-gets-murkier.html?haasFormId=e3a9446c-efb0-42e1-a999-f8680634d0ea&haasPage=0
Previous news article from this site: New research helps explain powerful particle accelerators
For more information about the Swedish particpants in Fermi:
The Swedish Fermi consortium - http://www.particle.kth.se/~tomiy/glast-sweden/index.html
Oskar Klein Centre: http://okc.albanova.se
NASA's Fermi website: http://fermi.gsfc.nasa.gov/
Original text: Per Larsson; English text: Jon Buscall
Content owner: External Relations Office
Created:
March 10, 2010
by
Paul Parker
Updated:
March 10, 2010
by
Paul Parker
