The fascination on pulsars has been long standing among astronomers. Since their discovery 50 years ago, pulsars have both impressed and baffled astronomers considerably.
These highly magnetized, rapidly spinning neutron stars are dense remnants of supernova explosions and are known to complete a single rotation in a couple of seconds. Pulsars also stand out for their lighthouse-like radio emissions with some of them discovered to be emitting high-energy gamma rays as well.
Matters Of Geometry
Thanks to recent images from NASA's Chandra X-ray Observatory on two pulsars – Geminga and B0355+54 – astronomers had new insights on many of the properties of pulsars.
The focus on pulsars' geometry intensified after the international team of astronomers, including researchers from Penn State University, started focusing on the distinctive emission signatures of pulsars. The study is published in The Astrophysical Journal.
Varied Emissions
The emission of gamma rays is not uniform in all pulsars. Stark differences have been observed in the shapes of radio and gamma-ray pulses, with some of the objects showing only one type of pulse or the other. Astronomers assume that these differences are rooted in the pulsar model and geometry.
"It's not fully understood why there are variations between different pulsars. One of the main ideas here is that pulse differences have a lot to do with geometry," noted Bettina Posselt, senior research associate in astrophysics and astronomy at Penn State.
She explained that the pulse variations are also linked to the spin of the pulsars and how the magnetic axis is aligned with the line of sight is determining whether they are seen or how they are seen.
Phenomenon Of Pulsar Wind Nebulae
The NASA images assisted in giving a broad idea of how pulsars rotate as they hurtle through space in high speeds at the rate of hundreds of kilometers.
The relation of type and volume of pulsar emissions with geometry gained strength from the study of Geminga and B0355+54. The images exposed their distinct emission signatures when their Pulsar wind nebulae (PWN) were studied.
The PWNs are donut-shaped rings known by the name tori, generated when the energized particles of the star remnants stream into the magnetic field around the equatorial plane of the pulsar, forming tail-like structures while rushing through the interstellar medium.
Thus, Chandra's X-ray facility gave a brilliant exposure of the faint structures with better specifics and a grand PWN view of the Geminga.
Role Of Orientation
Regarding B0355+54, Oleg Kargaltsev, assistant professor of physics, at George Washington University, also part of the study, noted that the pulsar's orientation had a lot do with its sight. He said a jet of radio waves was pointing to Earth giving a good view of bright beams while the gamma-ray emission has been moving in the plane of the sky and missing out the Earth.
