A group of researchers at the Max Planck Institutes for Gravitational Physics and Radio Astronomy, working with an international team, has discovered thanks to the Fermi Space Telescope a very special pulsar called J1838-0537. In fact, it emit only gamma rays and an anomaly in its rotation was detected.
Neutron stars are one of the possible results of the last stage of evolution of a star. If it explodes in a supernova and the mass that remains is at least 1.4 solar masses, it collapses into an object smaller than a white dwarf. Beyond 3 solar masses it would originate a black hole. In a neutron star, this mass is compacted in a sphere which may have a diameter of about 10-20 km (about 6-12 miles).
Typically, the huge magnetic field of a neutron star causes a very regular emission of electromagnetic pulses and for this reason it’s called a pulsar (PULSating stAR). Some of them emit very high energies pulses, in the range of gamma rays, but they’re difficult to identify because their characteristics are still poorly understood.
The Fermi Space Telescop was built specifically to study gamma rays emitted by various types of space objects. Gamma rays are absorbed in the upper Earth’s atmosphere so it was necessary to design a space telescope for this kind of research.
The researchers who are studying the pulsars that emit only gamma-ray had to use sophisticated algorithms originally developed for the analysis of gravitational waves to analyze the data from the Fermi Space Telescope. The analysis was performed by a powerful computer cluster, despite that this research was long.
One of the pulsar discovered is J1838-0537. According to analyzes carried out on this neutron star, it’s very young, around 5,000 years, and rotates about its own axis about seven times per second. It seemed to have disappeared after September 2009 but further data analyzes showed that in fact it just had a sort of hiccup.
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The rotation speed of J1838-0537 increased of 38 millionths of Hertz after this anomaly. It may seem very little but such a phenomenon had never been observed and because of this acceleration it was no longer recognized in the data of the Fermi Space Telescope. After making the necessary corrections in the algorithm research, J1838-0537 was found again.
Such anomalies have been discovered in the past in other pulsars but the causes are still unknown. One theory is that on the surface of these neutron stars “star quakes” happen that might affect their rotation. Another possibility is that there are interactions between the various layers of these stars which cause these anomalies.
Now researchers have figured out how to interpret the data from the Fermi Space Telescope to recognize anomalies of this type. Therefore we can hope that research on these very special stars will lead to new advances.
