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Posts Tagged ‘Fermi Gamma-ray Space Telescope’

Left-Handed Cosmic Magnetic Field Could Explain Missing Antimatter


An artist’s concept of the Fermi Gamma ray Space Telescope (FGST) in orbit. Credit: NASA

An artist’s concept of the Fermi Gamma ray Space Telescope (FGST) in orbit. Credit: NASA

The discovery of a ‘left-handed’ magnetic field that pervades the universe could help explain a long standing mystery – the absence of cosmic antimatter. A group of scientists, led by Prof Tanmay Vachaspati from Arizona State University in the United States, with collaborators at the University of Washington and Nagoya University, announce their result in Monthly Notices of the Royal Astronomical Society.

Planets, stars, gas and dust are almost entirely made up of ‘normal’ matter of the kind we are familiar with on Earth. But theory predicts that there should be a similar amount of antimatter, like normal matter, but with the opposite charge. For example, an antielectron or positron has the same mass as its conventional counterpart, but a positive rather than negative charge.

In 2001 Prof Vachaspati published theoretical models to try to solve this puzzle, which predict that the entire universe is filled with helical (screw-like) magnetic fields. He and his team were inspired to search for evidence of these fields in data from the NASA Fermi Gamma ray Space Telescope (FGST).

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NASA’s Fermi Satellite Finds Hints Of Starquakes In Magnetar ‘Storm’

October 24, 2014 Leave a comment

Image Credit: NASA's Goddard Space Flight Center/S. Wiessinger

Image Credit: NASA’s Goddard Space Flight Center/S. Wiessinger

NASA’s Fermi Gamma-ray Space Telescope detected a rapid-fire “storm” of high-energy blasts from a highly magnetized neutron star, also called a magnetar, on Jan. 22, 2009. Now astronomers analyzing this data have discovered underlying signals related to seismic waves rippling throughout the magnetar.

Such signals were first identified during the fadeout of rare giant flares produced by magnetars. Over the past 40 years, giant flares have been observed just three times — in 1979, 1998 and 2004 — and signals related to starquakes, which set the neutron stars ringing like a bell, were identified only in the two most recent events.

“Fermi’s Gamma-ray Burst Monitor (GBM) has captured the same evidence from smaller and much more frequent eruptions called bursts, opening up the potential for a wealth of new data to help us understand how neutron stars are put together,” said Anna Watts, an astrophysicist at the University of Amsterdam in the Netherlands and co-author of a new study about the burst storm. “It turns out that Fermi’s GBM is the perfect tool for this work.”

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NASA’s Fermi Space Telescope Reveals New Source Of Gamma Rays


Image Credit: NASA/DOE/Fermi LAT Collaboration

Image Credit: NASA/DOE/Fermi LAT Collaboration

Observations by NASA’s Fermi Gamma-ray Space Telescope of several stellar eruptions, called novae, firmly establish these relatively common outbursts almost always produce gamma rays, the most energetic form of light.

“There’s a saying that one is a fluke, two is a coincidence, and three is a class, and we’re now at four novae and counting with Fermi,” said Teddy Cheung, an astrophysicist at the Naval Research Laboratory in Washington, and the lead author of a paper reporting the findings in the Aug. 1 edition of the journal Science.

A nova is a sudden, short-lived brightening of an otherwise inconspicuous star caused by a thermonuclear explosion on the surface of a white dwarf, a compact star not much larger than Earth. Each nova explosion releases up to 100,000 times the annual energy output of our sun. Prior to Fermi, no one suspected these outbursts were capable of producing high-energy gamma rays, emission with energy levels millions of times greater than visible light and usually associated with far more powerful cosmic blasts.

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Black Hole ‘Batteries’ Keep Blazars Going And Going


Astronomers studying two classes of black-hole-powered galaxies monitored by NASA’s Fermi Gamma-ray Space Telescope have found evidence that they represent different sides of the same cosmic coin. By unraveling how these objects, called blazars, are distributed throughout the universe, the scientists suggest that apparently distinctive properties defining each class more likely reflect a change in the way the galaxies extract energy from their central black holes.

“We can think of one blazar class as a gas-guzzling car and the other as an energy-efficient electric vehicle,” said lead researcher Marco Ajello, an astrophysicist at Clemson University in South Carolina. “Our results suggest that we’re actually seeing hybrids, which tap into the energy of their black holes in different ways as they age.”

Active galaxies possess extraordinarily luminous cores powered by black holes containing millions or even billions of times the mass of the sun. As gas falls toward these supermassive black holes, it settles into an accretion disk and heats up. Near the brink of the black hole, through processes not yet well understood, some of the gas blasts out of the disk in jets moving in opposite directions at nearly the speed of light.

Blazars are the highest-energy type of active galaxy and emit light across the spectrum, from radio to gamma rays. They make up more than half of the discrete gamma-ray sources cataloged by Fermi’s Large Area Telescope, which has detected more than 1,000 to date. Astronomers think blazars appear so intense because they happen to tip our way, bringing one jet nearly into our line of sight. Looking almost directly down the barrel of a particle jet moving near the speed of light, emissions from the jet and the region producing it dominate our view.

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Fermi Data Tantalize With New Clues To Dark Matter


Image Credit: T. Linden, Univ. of Chicago

Image Credit: T. Linden, Univ. of Chicago

A new study of gamma-ray light from the center of our galaxy makes the strongest case to date that some of this emission may arise from dark matter, an unknown substance making up most of the material universe. Using publicly available data from NASA’s Fermi Gamma-ray Space Telescope, independent scientists at the Fermi National Accelerator Laboratory (Fermilab), the Harvard-Smithsonian Center for Astrophysics (CfA), the Massachusetts Institute of Technology (MIT) and the University of Chicago have developed new maps showing that the galactic center produces more high-energy gamma rays than can be explained by known sources and that this excess emission is consistent with some forms of dark matter.

The galactic center teems with gamma-ray sources, from interacting binary systems and isolated pulsars to supernova remnants and particles colliding with interstellar gas. It’s also where astronomers expect to find the galaxy’s highest density of dark matter, which only affects normal matter and radiation through its gravity. Large amounts of dark matter attract normal matter, forming a foundation upon which visible structures, like galaxies, are built.

No one knows the true nature of dark matter, but WIMPs, or Weakly Interacting Massive Particles, represent a leading class of candidates. Theorists have envisioned a wide range of WIMP types, some of which may either mutually annihilate or produce an intermediate, quickly decaying particle when they collide. Both of these pathways end with the production of gamma rays — the most energetic form of light — at energies within the detection range of Fermi’s Large Area Telescope (LAT).

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Gamma-Rays Tighten Window On Dark Matter Theories

February 28, 2014 Leave a comment

Observed data fitting the dark matter component, after subtracting all other components toward the Galactic Center.

Observed data fitting the dark matter component, after subtracting all other components toward the Galactic Center.

UC Irvine astrophysicists report that gamma-ray photons observed from the center of the Milky Way Galaxy are consistent with the intriguing possibility of dark matter annihilation, according to research submitted to the journal Physical Review D.

Kevork Abazajian, Nicolas Canac, Shunsaku Horiuchi and Manoj Kaplinghat analyzed data from NASA’s space-borne Fermi Gamma-ray Space Telescope and found that only a narrow range of dark matter models can produce an excess of gamma rays coming from the Milky Way. These gamma rays could be produced as particles of dark matter annihilate one another.

“The data provides a better-than 10 percent precise determination of the dark matter’s particle mass with the best estimates we have of what else is going on in the Galactic Center,” says Abazajian.

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NASA Spacecraft Take Aim At Nearby Supernova

January 27, 2014 Leave a comment

Image Credit: NASA/Swift/P. Brown, TAMU

Image Credit: NASA/Swift/P. Brown, TAMU

An exceptionally close stellar explosion discovered on Jan. 21 has become the focus of observatories around and above the globe, including several NASA spacecraft. The blast, designated SN 2014J, occurred in the galaxy M82 and lies only about 12 million light-years away. This makes it the nearest optical supernova in two decades and potentially the closest type Ia supernova to occur during the life of currently operating space missions.

To make the most of the event, astronomers have planned observations with the NASA/ESA Hubble Space Telescope and NASA’s Chandra X-ray Observatory, Nuclear Spectroscopic Telescope Array (NuSTAR), Fermi Gamma-ray Space Telescope, and Swift missions.

As befits its moniker, Swift was the first to take a look. On Jan. 22, just a day after the explosion was discovered, Swift’s Ultraviolet/Optical Telescope (UVOT) captured the supernova and its host galaxy.

Remarkably, SN 2014J can be seen on images taken up to a week before anyone noticed its presence. It was only when Steve Fossey and his students at the University of London Observatory imaged the galaxy during a brief workshop that the supernova came to light.

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