Unexplained Gamma Rays Pulse From Crab Nebula
The Crab Nebula
IMAGE BY NASA, ESA and Allison Loll/Jeff Hester (Arizona State University)
The Crab Nebula is full of surprises. Its genesis was spotted by Chinese scientists back in 1054, when nobody had any idea about what it could be, and it was only identified as a nebulous supernova several centuries later. In the mid 1900's, it was found to harbour a pulsar at its heart. And now, another enigma to solve - the Crab Pulsar is shooting out high energy gamma rays, and nobody knows why.
A team from the Santa Cruz Institute for Particle Physics in California measured the amount of gamma radiation being emitted by the pulsar.
While gamma rays themselves are typically a part of the electromagnetic radiation created by pulsars, the question is why these particular rays are so high-energy.
One of the scientists behind the research, Dr Nepomuk Otte, told the Science podcast that these findings could mean researchers need to go back to the drawing board on pulsar study.
"With this observation we now believe that the emission must come from much much further out in the magnetosphere, almost at the point where the magnetosphere rotates at the speed of light.
"[It]is very little understood how the magnetosphere behaves at these distances."
He also says that it is possible this discovery will ultimately prove that "all these previous explanations are completely wrong, and the standard picture that we have of a pulsar, how gamma emission works in a pulsar, is completely wrong and needs to be completely revised."
Current thought holds that particle emissions from pulsars begin in what is called the magnetosphere, or the complex electrical circuit created by the spinning pulsar, that emits electromagnetic particles at regular intervals.
The initial scans of the Crab pulsar were made with the FERMI space telescope in California, which can detect gamma rays with energy levels of up to 20 gigaelectronvolts (a unit of measurement used to quantify the level of energy to accelerate electrons through an electrical field). After reviewing the data, scientists suspected that rays energised well in excess of that amount were being missed.
The team then made use of the VERITAS telescope in Arizona, and found rays with an energy of more than 100 GeVs were being measured, which they say cannot be accounted for by current pulsar models.
According to the BBC, some even more powerful rays could rival the energy output of planet Earth's very own Large Hadron Collider.
One possible new model could be to posit that emission occurs from outside the magnetosphere of a pulsar, instead of inside, although Dr Otte says this idea would be "quite radical."
[via BBC, Science]