Pulsars are rapidly spinning neutron stars, extremely dense stars composed almost entirely of neutrons. They form when massive stars run out of fuel, collapse and explode.
Recently, NASA’s Chandra X-ray Observatory spotted a young pulsar blazing through the galaxy at nearly one million miles per hour. This pulsar is one of the fastest objects of its kind ever observed.
Chandra observed the pulsar racing through the remnants of the supernova that created it, G292.0+1.8, about 20,000 light-years away from Earth. The speed of this pulsar is about 30% higher than the previous estimate of the pulsar’s speed. This motion indicates that G292.0+1.8 and its pulsar may be much smaller than astronomers previously thought.
Xi Long of the Center for Astrophysics | Harvard and Smithsonian (CFA), which led the study, said, “We directly observed the motion of the pulsar in X-rays, something we could only do with Chandra’s very sharp vision. Because it is so far away, we had to measure the width of a quarter about 15 miles away to see this speed.
The scientists made the discovery after comparing Chandra images of G292.0+1.8 taken in 2006 and 2016. He saw a change in the status of pulsars in 10 years. Based on that, they calculated the speed of the pulsar by determining how far it is from the center of the explosion. They found that the pulsar is moving from the center of the supernova remnant to the bottom left at a speed of at least 1.4 million mph.
The research team also estimated that supernova G292.0+1.8 may have exploded about 2,000 years ago as seen from Earth 3,000 years ago, according to earlier calculations.
Daniel Patnaude, co-author of CFA also said, “We only have a handful of supernova explosions that also have a reliable historical record, so we wanted to test whether G292.0+1.8 could be added to this group.”
The team also determined – how did the supernova give the pulsar a powerful kick? There are two basic scenarios, both of which involve material not being expelled equally in all directions by the explosion. One theory is that the neutrinos produced in the explosion are ejected asymmetrically, while another is that the debris of the explosion is ejected asymmetrically. Because of the conservation of momentum principle, the pulsar will be kicked in the opposite direction if the material has a favorable direction.
This latest result would exceed the amount of neutrino asymmetry needed to explain the high speed, supporting the explanation that the asymmetry in the debris of the explosion gave the pulsar its kick. This agrees with the previous observation that the pulsar is moving inversely from the bulk of the X-ray-emitting gas.
The energy provided by this explosion to the pulsar was enormous. Although only about 10 miles across, the pulsar has a mass 500,000 times that of Earth, traveling at 20 times the speed of Earth orbiting the Sun.
CFA co-author Paul Plucinski also said, “This pulsar is about 200 million times more energetic than Earth’s speed around the Sun. It appears to have got its powerful kick because the supernova explosion is asymmetric.”
- Shi Long, Daniel J. Patnaude et al. Proper motion of pulsar J1124-5916 in the galactic supernova remnant G292.0+1.8. DOI: 10.48550/arXiv.2205.07951