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The Fermi Gamma-ray Space Telescope has found a new set of millisecond pulsars, which are typically very hard to find with other observatories such as radio telescopes. Detailed gamma-ray observations of these objects could even provide evidence for gravitational waves.

Talks continue through Thursday on scientific results from Fermi Gamma-ray Space Telescope involving pulsars, dark matter, supernova remnants, active galactic nuclei, gamma ray bursts, magnetars, blazars, and more.

Violent and massive events in our universe create brilliant gamma-ray displays that will keep the Fermi Gamma-ray Space Telescope busy for a decade. But recently, Fermi has turned its eyes back to Earth, where it can see evidence of Terrestrial Gamma Flashes, or TGFs, which are believed to originate at the tops of thunderstorm clouds. Fermi announced that it has detected positrons from TGFs, a first result and a major clue about what actually causes them.

AMESN writes "The Fermi Gamma-ray Space Telescope, launched last year, detects gamma rays from light years away, but recently it detected gamma rays from lightning on Earth. And the energy of the gamma rays is specific to the decay of positrons, which are the antimatter flavor of electrons. Finding antimatter in lightning surprised researchers and suggests the electric field of the lightning somehow got reversed."

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Two spots in the night sky look a bit brighter this week, thanks to collaborative efforts between the Large Area Telescope, which is the primary instrument aboard the Fermi Gamma Ray Space Telescope, and VERITAS, or the Very Energetic Radiation Imaging Telescope Array, a small array of ground-based telescopes in Amado, Arizona. The two collaborations announced last week the discovery of one new blazar and one likely blazar; if the second is confirmed these will be the third and fourth blazars that the observatories have collaborated to find.

WASHINGTON, D.C. — Designed to scan the heavens thousands to billions of light-years beyond the solar system, the Fermi Gamma-ray Space Telescope has now recorded some more down-to-Earth signals. During its first 14 months of operation, the flying observatory has detected 17 gamma-ray flashes associated with terrestrial lightning storms.

The flashes occurred just before, during and immediately after lightning strikes, as tracked by the World Wide Lightning Location Network.

During two recent lightning storms, Fermi recorded gamma-ray emissions of a particular energy that could only have been produced by the decay of energetic positrons, the antimatter equivalent of electrons. The observations are the first of their kind for lightning storms. Michael Briggs of the University of Alabama in Huntsville announced the puzzling findings Nov. 5 at the 2009 Fermi Symposium.

It’s a surprise to have found the signature of positrons during a lightning storm, Briggs said.

During lightning storms previously observed by spacecraft, energetic electrons moving toward the craft slowed down and produced gamma rays. The unusual positron signature seen by Fermi suggests that the normal orientation for an electric field associated with a lightning storm somehow reversed, Briggs said. Modelers are now working to figure out how the field reversal could have occurred. But for now, he said, the answer is up in the air.

Recording gamma-ray flashes — which have the potential to harm airplanes in storms — isn’t new. The first were found by NASA’s Compton Gamma-ray Observatory in the early 1990s. NASA’s RHESSI satellite, which primarily looks at X-ray and gamma-ray emissions from the sun, has found some 800 terrestrial gamma-ray flashes, Briggs noted.

Image: Flickr/thefost

See Also:

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• Mystery of Antimatter Source Solved – Maybe
• Balloon Circles Antarctica in Antimatter Hunt
• Preponderance of Positrons Points to Dark Matter
• Bring Back NASA’s Crazy Idea Factory
• Weird, Rare Clouds and the Physics Behind Them
• Mysterious, Glowing Clouds Appear Across America’s Night Skies

“Starburst” galaxies--sites of high numbers of star births and subsequent star deaths--have revealed themselves in gamma rays for the first time to the Fermi Gamma-ray Space Telescope. Combined with data from the VERITAS and HESS observatories, scientists are piecing together clues about the inner workings of some of the more exotic astrophysical objects.

Scientific American has a piece on speculation that dark matter may be behind diffuse radiation in the galactic center. Beginning in 2003, researchers led by Douglas Finkbeiner noticed a curious excess of microwave radiation in the WMAP data, after all known sources of such radiation were accounted for. Data from NASA's Fermi Gamma-Ray Space Telescope resulted in a similar anomaly in gamma rays. "A paper posted to the physics preprint Web site arXiv.org on October 26 and submitted to the Astrophysical Journal points to a possible signature of dark matter in the Milky Way, although the study's authors are careful to keep their observations empirical and table such speculation... In the new paper [the researchers] describe the Fermi gamma-ray haze and make the claim that it confirms the synchrotron origin of the WMAP microwave haze. And as with the microwave haze, the authors argue that the electrons responsible for the gamma-ray haze appear to originate from an unknown astrophysical process. ... 'We are absolutely in the process of exploring the Fermi haze in the context of dark matter physics,' [one of them] says."

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In its first year of operations, NASA's Fermi Gamma-ray Space Telescope has mapped the entire sky with unprecedented resolution and sensitivity in gamma-rays, the highest-energy form of light. On May 10, 2009 a pair of gamma-ray photons reached Fermi only 900 milliseconds apart after traveling for 7 billion years. Fermi's measurement gives us rare experimental evidence that space-time is smooth as Einstein predicted, and has shut the door on several approaches to gravity where space-time is foamy enough to interfere strongly with light.

A physics experiment using a super-fast explosion in a galaxy 7.3 billion light-years away has given scientists rare experimental evidence about the fundamental structure of space and time. The experiment was performed by a team that includes astrophysicists at Penn State University, who used NASA's Fermi Gamma Ray Space Telescope to study particles from the explosion moving at nearly the speed of light. The experiment confirmed aspects of Einstein's theories of gravity, which unite space and time in the concept of space-time. The team's research is published in the current early-online edition of the journal Nature and will be published at a later date in the print edition...