Neutron star: Merging spots observed on magnetar
Magnetars are among the most extraordinary objects in the universe. Despite their extremely high density, their surface is dynamic, as a long-term observation now shows.
NASA's NICER X-ray telescope, which orbits Earth attached to the outside of the International Space Station (ISS), has observed dynamic processes on the surface of magnetars: Patches of extremely powerful X-rays that move across the stellar remnant and merge in the process. Three such spots have now been tracked with the telescope, a team of researchers writes inThe Astrophysical Journal Letters.
The name NICER stands for Neutron star Interior Composition Explorer: The X-ray telescope should help to better understand the inner structure of neutron stars. These celestial bodies, which include magnetars, are very active in the X-ray region of the electromagnetic spectrum. They are formed when a massive star collapses under its own gravity into a dense sphere at the end of its life. In the process, a mass roughly equal to that of our Sun is compressed to about 20 kilometers, and electrons and protons fuse to form neutrons. The result is a structure whose density is so high that a teaspoonful of it on Earth would weigh as much as a whole mountain.
Magnetars stand out among neutron stars because of their extremely strong magnetic field. In their publication, the group led by George Younes of NASA Goddard Space Flight Center in Greenbelt, Maryland, now traces a special effect of this strong magnetic effect: It is apparently capable of literally "melting" the surface of the magnetar in some places. The three spots that NICER recorded in X-ray light would then have formed at such a point. They are probably due to loops, which can be found in a similar form on the surface of the sun. These loops emit X-rays and appeared in NICER's measurements as three separate peaks that repeated every 10.4 seconds - the magnetar's rotation period.
Until now, experts would have observed such bursts of radiation only in snapshots at different magnetars and at different times. In this case, however, the NICER telescope made it possible to track the spots from Oct. 10, 2020, to Nov. 17. This showed how two of the radiation peaks occurred at progressively smaller distances and eventually merged into one. After that, the magnetar had moved too close to the Sun as seen from NICER on the firmament to observe it further.
The celestial body is officially designated SGR 1830-0645 and lies in the constellation Shield. Its exact distance is not known, but it is estimated to be about 13,000 light-years from Earth.
How neutron stars are structured is a much discussed research question, which could be solved by such investigations. It is possible that quakes occur from time to time in their interior. These quakes, in turn, may be the long-sought source of the fast radio flashes.
Spectrum of Science
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