Brightest, farthest pulsar ever detected

The discovery of a pulsar that is ten times brighter than the previous record holder is causing astronomers to rethink what we know about stars.

An image showing spiral galaxy NGC 5907, in which the record breaking pulsar resides. The inset box shows how the pulsar takes just 1.13 seconds to complete one spin. Copyright: ESA/XMM-Newton; NASA/Chandra and SDSS

Astronomers have discovered a kind of spinning star called a pulsar that is the brightest ever observed, and ten times brighter than the previous record holder.

Pulsars are the compacted, dense remnants of massive stars that have exploded, and spin quickly while sending out pulses of radiation into space.


ESA’s XMM-Newton X-ray space observatory has spotted one such pulsar, named NGC 5907 X-1, that is a thousand times brighter than previously thought possible, and releases the same amount of energy in one second as our Sun does in 3.5 years.

It is also the farthest pulsar from Earth ever detected, some 50 million lightyears away.

“Before, it was believed that only black holes at least ten times more massive than our Sun feeding off their stellar companions could achieve such extraordinary luminosities, but the rapid and regular pulsations of this source are the fingerprints of neutron stars and clearly distinguish them from black holes,” says lead author Gian Luca Israel, from INAF-Osservatorio Astronomica di Roma, Italy.

The discovery is also significant because the pulsar’s spin rate has changed from 1.43 seconds per rotation in 2003 to 1.13 seconds in 2014.

It is thought that such a rapid change in speed must be the result of a star consuming mass from a companion star.


“It is 1,000 times more luminous than the maximum thought possible for an accreting neutron star,” says Israel, “so something else is needed in our models in order to account for the enormous amount of energy released by the object.”