Pulsars

A pulsar is a rapidly rotating neutron star, the endpoint of some stars' life cycle. Originally detected at radio wavelengths, they were detected at in the gamma-ray range a few years later. In fact, pulsars were the first astronomical sources detected at gamma-ray energies. Pulsars have tremendously intense magnetic fields and from the poles of these magnetic fields they emit narrow beams of radiation and accelerate particles to high velocities. We detect this radiation on Earth as regular pulses as the beam sweeps by similar to the way a lighthouse light sweeps past.

Chandra Observatory X-ray image of the Crab Nebula pulsar. Schematic of gamma-ray pulsar.

The first image is a Chandra Observatory X-ray image of the Crab Nebula pulsar, while the second one is schematic of gamma-ray pulsar. Courtesy GLAST at Sonoma State University.

EGRET observations showed that the gamma-ray emissions dominate the total radiation emitted from young pulsars. Moreover, EGRET data showed that variations in the high-energy gamma-ray emission arise from the changing view into the pulsar magnetosphere as the neutron star spins. GLAST will have the ability to map the pulsar magnetosphere and provide unique information regarding the physics of the pulsar emission. GLAST observations may be able to answer the question of how the particles in the beams are being accelerated.