An article published in the journal “Science” describes the study of the first gamma-ray emitting pulsar discovered outside the Milky Way. Cataloged as PSR J0540-6919, it’s part of an area full of stars known as the Tarantula Nebula or 30 Doradus within the Large Magellanic Cloud, a small satellite galaxy of the Milky Way. The gamma rays emission from this pulsar was identified by the LAT (Large Area Telescope), one of the instruments of the Fermi gamma-ray space telescope.
In the past, in the Tarantula Nebula two pulsars were discovered well because besides PSR J0540-6919, discovered by the Einstein satellite, there’s also another one cataloged as PSR J0537-6910, discovered by the Rossi X-ray Timing Explorer (RXTE) satellite. However, it took more than six years to realize that PSR J0540-6919 emitted gamma rays as well.
Pulsars are neutron stars, what remains after a supernova, the explosion of a star with a mass greater than the Sun’s. The remaining core collapses and one of the consequences may be the characteristic pulse that gives its name to these celestial bodies.
In recent years many pulsars that emit gamma rays have been discovered while before the launch of the Fermi space telescope, in 2008, only seven such cases were known. Thanks to the experience accumulated in the use of Fermi, a new analysis of the data collected by the LAT allowed to understand that among the emissions coming from the pulsar PSR J0540-6919 there were gamma rays.
This new study of the pulsar PSR J0540-6919 determined that its gamma emissions are the most powerful so far detected, with an intensity 20 times higher than those of the pulsar at the center of the Crab Nebula. These two pulsar have several things in common, from an estimated age of not many centuries, much less than most known pulsars, the intensity of their magnetic field and their spinning speed.
Further studies of the pulsar PSR J0540-6919, its similarities and differences compared to that in the Crab Nebula will allow to better understand the extreme physics taking place in young pulsars. These are objects that are not as extreme as the black holes but enough to be useful to test our knowledge of physics and astrophysics.
