Intensity of Gamma Rays Emitted by Crab Pulsar Baffles Scientists

A group of international astrophysicists, using the Very Energetic Imaging Telescope Array System (VERITAS), spotted gamma rays with energies exceeding 100 billion electron-volts, emitted from the Crab Pulsar supernova. The fast spinning Crab Pulsar supernova was discovered in 1968 and was the first to be connected with a supernova remnant. The Crab pulsar's emissions were more than 100 gigaelectronvolts which are100 billion times more energetic than visible light.

The emitted rays were observed by scientists around 107 hours over a course of three years at the Whipple Observatory in Arizona. These rays are invisible to the human eye and the only way telescopes on earth can detect their path is by observing the path they take in the planet's atmosphere. The Cherenkov telescopes used at VERITAS detect the faint and extremely short flashes of blue light emitted by these particles. Apparently, the pulsar's humongous magnetic field gathers up particles and accelerates them - in a process much like particle accelerators here on Earth.

VERITAS member and Washington University physicist, Henric Krawczynski, said the pulsed gamma rays had energies "between 100 and 400 billion electronvolts (GeV)." "This is far higher than the highest Crab Nebula radiation level previously detected, which was around 25 GeV. We presented the results at a conference and the entire community was stunned," said Krawczynski.

The highly energized gamma rays are emitted from the center of the pulsar, which is a spinning neutron star that is born from the collapsed core of a massive star. The pulsar's enormous magnetic field is known to gather up particles and accelerate them. Scientists believe that beams of radiation are generated from the pulsar's spinning magnetic fields that rotate at about 30 times a second.

Nepomuk Otte, a corresponding author of the study and postdoctoral researcher at the University of California, Santa Cruz, was told by some researchers that he was crazy to look for pulsar emission in this energy realm.

"It turns out that being persistent and stubborn helps," Otte said. "These results put new constraints on the mechanism for how the gamma-ray emission is generated."

The most recent observation has left scientists puzzled as to the details of how the most energetic particles are formed, and it shows how elusive the complete understanding of the process is.