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February
10, 2009: NASA's Swift and Fermi spacecraft are monitoring
a neutron star 30,000 light years from Earth that is drawing
attention to itself with a series of powerful gamma-ray flares.
 "At
times, this remarkable object has erupted with more than a
hundred flares in as little as 20 minutes," said Loredana
Vetere, who is coordinating the Swift observations at Pennsylvania
State University. "The most intense flares emitted more
total energy than the sun does in 20 years."
Right:
An artist's concept of the flare star in action. Credit: NASA/Goddard
Space Flight Center Conceptual Image Lab. [more]
The
star, known as SGR J1550-5418, lies in the southern constellation
Norma. It began a series of modest eruptions on Oct. 3, 2008,
settled down for a while, then roared back to life on Jan.
22, 2009, with an intense episode.
Because
of its rapid-fire outbursts and gamma-ray spectrum, astronomers
classify the object as a "soft-gamma-ray repeater"
-- only the sixth known. In 2004, a giant flare from another
soft-gamma-ray repeater was so intense it ionized Earth's
upper atmosphere from 50,000 light-years away: more.
Using
data from an X-ray telescope onboard Swift, Jules Halpern
at Columbia University captured the first "light echoes"
ever seen from a soft-gamma-ray repeater. Images acquired
when the latest flaring episode began show what appear to
be expanding halos around the source. Multiple rings form
as X-rays interact with dust clouds at different distances.
Click on the image to play a 6-day movie:
Above:
Swift's X-Ray Telescope (XRT) captured an apparent expanding
halo around the flaring neutron star SGR J1550-5418. The halo
formed as X-rays from the brightest flares scattered off of
intervening dust clouds. Credit: NASA/Swift/Jules Halpern,
Columbia Univ. [more]
Scientists
think the source of the flares is a spinning neutron star--the
superdense, city-sized remains of a supernova. Although only
about 12 miles across, a neutron star contains more mass than
the sun. This particular neutron star is believed to be a
"magnetar," a neutron star with an incredibly intense
magnetic field.
A
popular theory of soft-gamma-ray repeaters holds that flares
are caused by "starquakes" in the outer rigid crust
of the magnetar. As a magnetar's colossal magnetic field shifts,
it strains the crust with monstrous magnetic forces, often
breaking it. When the crust snaps, it vibrates with seismic
waves like in an earthquake and emits a flash of gamma-rays.
No
one is really certain of the details, however, and much work
remains to be done to understand these powerfully hyperactive
stars.
NASA's
Fermi Gamma-ray Space Telescope, launched in June 2008, is
ideal for this work. "The ability of Fermi's gamma-ray
burst monitor to resolve the fine structure within these events
will help us better understand how magnetars unleash their
energy," said Chryssa Kouveliotou, an astrophysicist
at NASA's Marshall Space Flight Center in Huntsville, Ala.
The object has triggered Fermi's gamma-ray burst monitor more
than 95 times since Jan. 22nd.
NASA's
Wind satellite, the joint NASA-Japan Suzaku mission, and the
European Space Agency's INTEGRAL satellite also have detected
flares from SGR J1550-5418.
The
flashes continue! Stay tuned to Science@NASA for updates.
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Editor: Dr.
Tony Phillips | Credit: Science@NASA
| more
information |
| Mission
home pages: Swift,
Fermi
Solar
Flares on Steroids (Science@NASA)
Crusty
Star Makes its Presence Felt (Science@NASA)
Magnetar
Discovery Solves 19-year Mystery (Science@NASA)
Credits:
NASA's Goddard Space Flight Center in Greenbelt, Md.,
manages the Swift satellite. It is being operated in
collaboration with partners in the U.S., the United
Kingdom, Italy, Germany and Japan. NASA's Fermi Gamma-ray
Space Telescope is an astrophysics and particle physics
observatory developed in collaboration with the U.S.
Department of Energy and with important contributions
from academic institutions and partners in France, Germany,
Italy, Japan, Sweden, and the U.S.
NASA's
Future: US
Space Exploration Policy |
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