Hubble Finds New Features Around Neutron Star

Infrared light emission from a nearby neutron star could indicate never-before-seen features.

Neutron Star, illustration.
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Infrared light emission from a nearby neutron star could indicate never-before-seen features.

A new paper out in The Astrophysical Journal details the findings of an international team of astronomers regarding RXJ0806.4–4123, a relatively close neutron star in a cluster called the “Magnificent Seven.” In it, researchers from Penn State, Sabanci University in Turkey, and the University of Arizona detail an unusual infrared emission from the pulsar that indicates the possibility of never-before-seen features.

Bettina Posselt is an associate research professor of astronomy and astrophysics at Penn State and the lead author of the paper, entitled “Discovery of Extended Infrared Emission around the Neutron Star RXJ0806.4–4123.”

We observed an extended area of infrared emissions around this neutron star… 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.

Normally, extended emissions from pulsars are found through the use of radio telescopes and X-ray detectors, but this is the first time scientists have seen an emission only in the infrared portion of the electromagnetic spectrum. The emission indicates that there is additional physical material surrounding the pulsar out to a diameter of 200 AU, or about 18 billion miles, causing interference in the infrared signal.

One possible explanation is that there is a “fallback disk” comprised of material left over from the original star’s supernova explosion. If such a disk of cosmic dust exists and is oriented so that the disk is between the pulsar and the Earth, it could cause interference in the infrared spectrum that would fit the observations.

Another possible explanation is the idea of a “pulsar wind nebula.” A pulsar wind nebula forms when a neutron star has a strong magnetic field, and particles are accelerated in the electric field produced by it. Since pulsars, like all astronomical objects, hurtle through space at very high speeds, the pulsar would effectively push the wind through the interstellar medium, creating a shock wave — much like that produced when a jet flying in the Earth’s atmosphere breaks the speed of sound. The shock wave could conceivably scatter the emissions to fit the pattern observed by the scientists.

When the James Webb telescope launches in 2021 as a replacement for the Hubble, it will provide additional tools to observe pulsars in the infrared portion of the electromagnetic spectrum, increasing our knowledge about how they form and the life cycles they go through. When fully deployed, the Webb telescope will exist at a relatively stable location between the Earth and sun known as a La Grange point, nearly 1 million miles from Earth. This location should provide unprecedented imagery due to lack of interference from nearby celestial bodies, but repairs — like those performed on the faulty Hubble telescope mirror — will be impossible due to the extreme distance from Earth.