Crab Nebula Erupts in a Superflare

Article written: 11 May , 2011
Updated: 24 Dec , 2015


From a NASA press release:

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. Several other satellites also made observations, which has astonished astronomers by revealing unexpected changes in X-ray emission the Crab, once thought to be the steadiest high-energy source in the sky.

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.

X-ray data from NASA's Fermi, RXTE, and Swift satellites and the European Space Agency's International Gamma-Ray Astrophysics Laboratory (INTEGRAL) confirm that the Crab Nebula's output has declined about 7 percent in two years at energies from 15,000 to 50,000 electron volts. They also show that the Crab has brightened or faded by as much as 3.5 percent a year since 1999. Fermi's Large Area Telescope (LAT) has detected powerful gamma-ray flares (magenta lines) as well. (Image credit: NASA's Goddard Space Flight Center)

“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.”

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.

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.

It was also observed by NASA’s Rossi X-Ray Timing Explorer (RXTE) and Swift satellites and the European Space Agency’s International Gamma-Ray Astrophysics Laboratory (INTEGRAL). The results confirm a real intensity decline of about 7 percent at energies between 15,000 to 50,000 eV over two years. They also show that the Crab has brightened and faded by as much as 3.5 percent a year since 1999.

“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 galactic 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.

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9 Responses

  1. Anonymous says

    “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”

    Sounds very thinly veiled EU story again, why are we giving these trouble makers more ammunition for thier crackpot theories??

    Sounds very much like thier fouvourite “electric discharge” aka lightning or a cosmic thunder bolt.

    • Member
      IVAN3MAN_AT_LARGE says

      Sounds very much like pious fundamentalists who see an image of Jesus in an oil stain or cheese-on-toast!

    • Rob Hemmings says

      Has nothing to do with EU – sick of hearing mention of it in these comments. Our own Sun accelerates particles when magnetic flux lines collapse (hence CMEs) so just imagine what can go on with matter from an accretion disc falling into and being accelerated by highly distorted magnetic fields associated with a neutron star!

  2. Roman Rodák says

    100-times greater energies than LHC and no micro black holes or strangelets? what a pity…

  3. Anonymous says

    Heres is a Purely Fictional Interpretation.

    The crab nebula is an construct designed to accelerate matter to light speeds. The supernova has purpose, The suns having created elements of super dense matter, explode into clouds that can then be accelerated towards distant civilizations that have used up all available materials. What better way for advanced societies to find and collect exotic matter. 🙂

    Well it might explain where the crab nebula’s missing matter has gone.
    (no flaming plz, just a sci-fi run of the imagination)

    • Anonymous says

      Any civilization that can manipulate pulsars can probably do transmutation of elements. No need to go charging half way across the galaxy to find hardtogetium. just make it your self.

  4. Anonymous says

    The photons are emitted by Bremsstrahlung radiation, or its relativistic form synchrotron emission. We do not know for sure what accelerates the electrons, but it might not be unreasonable to think it is some form of shock wave. There is likely an accretion disk around the neutron star that is not stationary in its configuration. Transient fluctuations might result in high energy events, such as due to the implosion of large amounts of matter onto the neutron star.


  5. Peter says

    Be fair guys, at least this one wasn’t couched up with the old theoretical dunderhead nonsense of many announcements.
    There is a logical explanation consistent with the observations. The active toroid (tokamak) nucleus (the common smaller version of a super massive galactic AGN) is sucking in the old matter and blasting it out both ways, exactly as Galactic Quasars do. Check out the SDSS, there are thousands more out there! The ‘pulse’ was just from a large lump of mass sucked in (by the helical em field – see Hoft Fibration). Take a close looki at the Cartwheel Galaxy and tell me those tangential ‘spokes’ are from an explosion (flat!?) rather than accretion from the ring!

    OK Science hasn’t put the whole logic together yet, it’s in the Discrete Field Model, (DFM) which also logically predicted the Lense-Thirring effect Gravity Probe B has just confirmed, but, ok, this has not been accepted by mainstream science yet. but we all know about inertia.
    Another prediction is that if any ‘knot’ can be picked up within the jet it will be found apparently superluminal or damn close, within the stream.

    Peter J

    • Jon Hanford says

      “Take a close looki[sic] at the Cartwheel Galaxy and tell me those tangential ‘spokes’ are from an explosion (flat!?) rather than accretion from the ring!”

      Not sure what you refer to here but the collisional nature of the Cartwheel Galaxy=AM 0035-335 has been confirmed both observationally and through computer modelling. See Mapelli et al and references therein:

      Do you have any recent refs (peer reviewed in a relevant journal) that specifically suggest AM 0035-335 formed in an alternate manner?

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