NASA's Fermi Spots 'Superflares' in the Crab Nebula
The famous Crab Nebula supernova remnant has erupted in an enormous flare five times more powerful than any previously seen from the object. The outburst was first detected by NASA's Fermi Gamma-ray Space Telescope on April 12 and lasted six days.
The nebula, which is the wreckage of an exploded star whose light reached Earth in 1054, is one of the most studied objects in the sky. At the heart of an expanding gas cloud lies what's left of the original star's core, a superdense neutron star that spins 30 times a second. With each rotation, the star swings intense beams of radiation toward Earth, creating the pulsed emission characteristic of spinning neutron stars (also known as pulsars).
Apart from these pulses, astrophysicists regarded the Crab Nebula to be a virtually constant source of high-energy radiation. But in January, scientists associated with several orbiting observatories -- including NASA's Fermi, Swift and Rossi X-ray Timing Explorer -- reported long-term brightness changes at X-ray energies.
Scientists think that the flares occur as the intense magnetic field near the pulsar undergoes sudden restructuring. Such changes can accelerate particles like electrons to velocities near the speed of light. As these high-speed electrons interact with the magnetic field, they emit gamma rays in a process known as synchrotron emission.
To account for the observed emission, scientists say that the electrons must have energies 100 times greater than can be achieved in any particle accelerator on Earth. This makes them the highest-energy electrons known to be associated with any cosmic source.
Based on the rise and fall of gamma rays during the April outbursts, scientists estimate that the size of the emitting region must be comparable in size to the solar system. If circular, the region must be smaller than roughly twice Pluto's average distance from the sun.NASA's Fermi Spots 'Superflares' in the Crab Nebula
Like a July 4 fireworks display a young, glittering collection of
stars looks like an aerial burst. The cluster is surrounded by
clouds of interstellar gas and dust - the raw material for new
star formation. The nebula, located 20,000 light-years away in
the constellation Carina, contains a central cluster of huge, hot
stars, called NGC 3603.
This environment is not as peaceful as it looks. Ultraviolet
radiation and violent stellar winds have blown out an
enormous cavity in the gas and dust enveloping the cluster,
providing an unobstructed view of the cluster.</br>
Most of the stars in the cluster were born around the same
time but differ in size, mass, temperature, and color. The
course of a star's life is determined by its mass, so a cluster of
a given age will contain stars in various stages of their lives,
giving an opportunity for detailed analyses of stellar life cycles.
NGC 3603 also contains some of the most massive stars
known. These huge stars live fast and die young, burning
through their hydrogen fuel quickly and ultimately ending their
lives in supernova explosions.</br>
Star clusters like NGC 3603 provide important clues to
understanding the origin of massive star formation in the
early, distant universe. Astronomers also use massive clusters
to study distant starbursts that occur when galaxies collide,
igniting a flurry of star formation. The proximity of NGC 3603
makes it an excellent lab for studying such distant and
momentous events.</br>
This Hubble Space Telescope image was captured in August
2009 and December 2009 with the Wide Field Camera 3 in
both visible and infrared light, which trace the glow of sulfur,
hydrogen, and iron.</br>
The Hubble Space Telescope is a project of international cooperation
between NASA and the European Space Agency. NASA’s Goddard Space Flight
Center manages the telescope. The Space Telescope Science Institute
(STScI) conducts Hubble science operations. STScI is operated for NASA
by the Association of Universities for Research in Astronomy, Inc. in
Washington, D.C.
</br>See:Starburst Cluster Shows Celestial Fireworks
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