An article published in the journal “Monthly Notices of the Royal Astronomical Society” describes the discovery of the first pulsar in the Andromeda galaxy. A team led by Paolo Esposito of INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica, Milan, Italy, found this elusive object using the archives of observations made with ESA’s XMM-Newton space telescope.
Pulsars are one of possible products of of what remains after the collapse of a star and the supernova that follows it. This is a class of spinning neutron stars that were called pulsars because they emit regular pulses that can be detected on Earth. They’re well known but none had been discovered in the Andromeda galaxy yet.
Astronomers use M31, one of the alternate names of the Andromeda galaxy, because it’s close in astronomical terms – meaning “only” 2.5 million light years away – and has a structure similar to that of the Milky Way, which is the reason why it’s considered a kind of big sister because it’s larger than our galaxy. Despite decades of observations, only now astronomers were able to discover a pulsar in Andromeda.
The research in the archives of the data collected by the XMM-Newton space telescope took place within the EXTraS (Exploring the X-ray transient and variable Sky) project, which is specifically intended to analyze systematically those data. One result was the discovery of the pulsars in the Andromeda galaxy, which was identified as 3XMM J004301.4+413017.
This pulsar has a rotation period of 1.2 seconds and has a companion which seems to be feeding on. The pulsar’s traces were found thanks to the X-rays it emitted but it took a meticulous research that was carried out on all the archives of Andromeda’s observations between 2000 and 2013.
There are few certainties regarding this discovery and still many questions. There is a pulsar that has a companion but it’s unclear what kind of star it is. That seems to be an unusual binary system but more data are needed to gain a better understanding of its nature. Now that it’s been identified, it will be easier to look for more information in the XMM-Newton and other telescopes’ archives but also carry out targeted observations.
