Illustrated GIF showing a neutron star with a circum-pulsar disk. If seen at the proper angle the scattered emission from the inner part of the disk could produce the extended infrared emission observed by astronomers around the neutron star RX J0806.4-4123. Credit: Nahks Tr'Ehnl, Penn State
A bizarre pulsar emanating from a nearby neutron star, RX J0806.4-4123, is giving off a strange light and scientists are unclear about what is causing it.
A team of researchers from Penn State University found the strange emission using the Hubble Space Telescope and noticed that the pulsar is only giving off infrared radiation, at a great distance.
“This particular neutron star belongs to a group of seven nearby X-ray pulsars – nicknamed ‘the Magnificent Seven’ – that are hotter than they ought to be considering their ages and available energy reservoir provided by the loss of rotation energy,” said in a statement Bettina Posselt, associate research professor of astronomy and astrophysics at Penn State and the lead author of the paper.
Posselt continued: “We observed an extended area of infrared emissions around this neutron star – named RX J0806.4-4123 – the total size of which translates into about 200 astronomical units (or 2.5 times the orbit of Pluto around the Sun) at the assumed distance of the pulsar.”
Neutron stars are remnants of supernova explosions and contain about 1.5 times the mass of the Sun – equivalent to about half a million Earths – inside a ball 12 miles across, according to NASA.
NASA's James Webb Space Telescope, set to launch in 2021, will replace the Hubble and give researchers further insights into neutron stars like the one described above. The Hubble, which was built by NASA with contributions from the European Space Agency, has been in low Earth orbit since 1990.
The findings were published in the Astrophysical Journal, where two potential explanations were proposed: there is a disk of material surrounding the star or there is an energetic wind blowing off the neutron star, interacting with gas in space, which would ultimately create a “pulsar wind nebula."
If it is indeed a disk, the matter would've come from "the progenitor massive star," Posselt said, before adding that if it interacted with the neutron star, it could have heated the pulsar, slowing its rotation and changing how neutron stars evolve.
The energetic wind explanation is a bit more complex, Posselt explained.
“A pulsar wind nebula would require that the neutron star exhibits a pulsar wind,” said Posselt. “A pulsar wind can be produced when particles are accelerated in the electric field that is produced by the fast rotation of a neutron star with a strong magnetic field.
Posselt continued: "As the neutron star travels through the interstellar medium at greater than the speed of sound, a shock can form where the interstellar medium and the pulsar wind interact. The shocked particles would then radiate synchrotron emission, causing the extended infrared emission that we see. Typically, pulsar wind nebulae are seen in X-rays and an infrared-only pulsar wind nebula would be very unusual and exciting.”
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