MessageToEagle.com - The famous Crab Nebula supernova remnant has erupted in an enormous flare five times more
powerful than any flare previously seen from the object. On April 12, NASA's Fermi Gamma-ray Space Telescope first
detected the outburst, which lasted six days.
The nebula is the wreckage of an exploded star that emitted light which reached Earth in the year 1054. It is
located 6,500 light-years away in the constellation Taurus. At the heart of an expanding gas cloud lies what
is 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 believed the Crab Nebula was 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.
"The Crab Nebula hosts high-energy variability that we're only now fully appreciating," said Rolf Buehler, a member of the Fermi Large Area Telescope (LAT) team at the Kavli Institute for Particle Astrophysics and Cosmology, a facility jointly located at the Department of Energy's SLAC National Accelerator Laboratory and Stanford University.
Since 2009, Fermi and the Italian Space Agency's AGILE satellite have detected several short-lived gamma-ray flares at energies greater than 100 million electron volts (eV) -- hundreds of times higher than the nebula's observed X-ray variations. For comparison, visible light has energies between 2 and 3 eV.
On April 12, Fermi's LAT, and later AGILE, detected a flare that grew about 30 times more energetic than the nebula's normal gamma-ray output and about five times more powerful than previous outbursts. On April 16, an even brighter flare erupted, but within a couple of days, the unusual activity completely faded out.
"These superflares are the most intense outbursts we've seen to date, and they are all extremely puzzling events," said Alice Harding at NASA's Goddard Space Flight Center in Greenbelt, Md. "We think they are caused by sudden rearrangements of the magnetic field not far from the neutron star, but exactly where that's happening remains a mystery."
A Hubble visible light image of the Crab Nebula inset against a full-sky gamma ray map showing the location of the nebula (crosshairs). Credit: NASA
The Crab's high-energy emissions are thought to be the result of physical processes that tap into the neutron star's rapid spin. Theorists generally agree the flares must arise within about one-third of a light-year from the neutron star, but efforts to locate them more precisely have proven unsuccessful so far.
There are strange goings-on in the Crab Nebula. On April 12, 2011, NASA's Fermi Gamma-ray Space Telescope
detected the most powerful in a series of gamma-ray flares occurring somewhere within the supernova remnant.
Since September 2010, NASA's Chandra X-ray Observatory routinely has monitored the nebula in an effort to identify X-ray emission associated with the outbursts. When Fermi scientists alerted astronomers to the onset of a new flare, Martin Weisskopf and Allyn Tennant at NASA's Marshall Space Flight Center in Huntsville, Ala., triggered a set of pre-planned observations using Chandra.
"Thanks to the Fermi alert, we were fortunate that our planned observations actually occurred when the flares were brightest in gamma rays," Weisskopf said. "Despite Chandra's excellent resolution, we detected no obvious changes in the X-ray structures in the nebula and surrounding the pulsar that could be clearly associated with the flare."
Scientists think 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.
To account for the observed emission, scientists say 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.
Abnormal Star Discovered In The 'Forbidden Zone'
A team of astrophysicists from Germany, France and Italy have discovered in the constellation Leo is an old star.
The star's existence raised at once many questions for scientists.
The object is definitely not as its "contemporaries" that appeared immediately after the Big Bang event.
Possible Water In The Atmosphere Of A Super-Earth
Four CfA astronomers, Zachory Berta, David Charbonneau, Jean-Michel Desert, and Jonathan Irwin, together with six colleagues,
used the Hubble Space Telescope to probe the atmosphere around the transiting super-Earth known as GJ1214b.
This exoplanet has a mass of 6.5 Earth-masses and a radius of 2.7 Earth-radii, and it orbits a small M-dwarf star (its diameter
is only 21% of the Sun's).
Astronomical Mystery - Tremendous Explosion And Appearance Of Odd Rings
Twenty five years ago, on 1987 February 23, the brightest supernova of modern times was observed in the Large Magellanic Cloud.
The collision occurred at speeds near 60 million kilometers per hour and shock-heats the ring material causing it to glow.
Over time, astronomers have watched and waited for the expanding debris from this tremendous stellar explosion to crash into previously expelled material...
Doesn't Secret Dark Matter Exist?
The more scientists study dark matter they know lesser and are not particularly optimistic about their results.
After completing this study, we know less about dark matter than we did before," said Matt Walker, of the Harvard-Smithsonian Center for Astrophysics.
A mysterious and still unknown substance is totally invisible in the Universe and reveals its presence only through its gravitational pull...
Dwarf Irregular Galaxy That Forces Scientists To Re-Evaluate Old Theory
Astronomers from Center for Astrophysics of the University of Porto, Portugal and Oskar Klein Centre, Stockholm University, Sweden come up
with new findings regarding one of the most studied objects - the dwarf galaxy I Zw 18.
The results led the scientists to the conclusion that this enigmatic blue compact dwarf might force
astronomers to review current galaxy formation models and much of what is known about galaxy formation and evolution might need substantial revision.
The Eyes Of A Future Alien Astronomer - What Will They See?
Have you ever wondered what the Universe will look like for a future alien astronomer?
It will in fact be entirely different from what it is today.
One trillion years from now, an alien astronomer in our galaxy will have great difficulties figuring out how the universe began.
The Milky Way will have merged with the Andromeda galaxy to form the Milkomeda galaxy. Many of its stars, including our Sun, will have burned out.
Violent Dragon Clash Billions Of Years Ago
NGC 5907 is sometimes called the "Splinter" or Knife Edge Galaxy because of its unusual appearance.
It is a spiral galaxy lying in the Dragon constellation,
about 40 million light-years from Earth that could have been formed through a gigantic collision of galaxies, 8 to 9 billion years ago.