Astronomers have spotted the first ever spinning neutron star to be observed in the nearby Andromeda Galaxy.

Andromeda is a favourite object among observers because of its proximity and similarity to our own, and has been studied for decades by astronomers looking for clues as to the formation and evolution of the Milky Way.


But despite this extensive study, no observations had ever been made of a spinning neutron star in Andromeda, until now.

Neutron stars are the very dense remains of a massive star following its explosion as a supernova. They often spin incredibly fast, sending pulses of radiation towards Earth called ‘pulsars’.

Often, neutron stars are found as one part of a stellar couple and feed off their partner, causing the neutron star to spin faster.

These spinning neutron stars are common in the Milky Way, but had eluded astronomers searching for them in Andromeda.

Now, one such candidate has been found following rigorous searching through data from the XMM-Newton X-ray telescope.

The star spins every 1.2 seconds and seems to be feeding on another star that orbits it every 1.3 days.

“We were expecting to detect periodic signals among the brightest X-ray objects in Andromeda, in line with what we already found during the 1960s and 1970s in our own Galaxy,” says Gian Luca Israel from INAF-Osservatorio Astronomica di Roma, Italy.

“But persistent, bright X-ray pulsars like this are still somewhat peculiar, so it was not completely a sure thing we would find one in Andromeda.

“We looked through archival data of Andromeda spanning 2000–13, but it wasn’t until 2015 that we were finally able to identify this object in the galaxy’s outer spiral in just two of the 35 measurements.”


Did you know that the Andromeda Galaxy is set to merge with the Milky Way in the distant future? Find out more in our guide to the Andromeda-Milky Way collision.