Astronomers have identified a pulsar spinning at more than 42,000 revolutions per minute, making it the second-fastest known.

The new object, named PSR J0952-0607 — or J0952 for short — is classified as a millisecond pulsar and is located between 3,200 and 5,700 light-years away in the constellation Sextans.

The pulsar contains about 1.4 times the Sun’s mass and is orbited every 6.4 hours by a companion star that has been whittled away to less than 20 times the mass of the planet Jupiter, according to a study published online in the The Astrophysical Journal Letters.

The discovery was made with the Netherlands-based Low Frequency Array (LOFAR) radio telescope by following up on mysterious high-energy sources mapped out by NASA’s Fermi Gamma-ray Space Telescope.

“Roughly a third of the gamma-ray sources found by Fermi have not been detected at other wavelengths,” said Elizabeth Ferrara, a member of the discovery team at NASA’s Goddard Space Center in Greenbelt, Maryland.

“Many of these unassociated sources may be pulsars, but we often need follow-up from radio observatories to detect the pulses and prove it,” Ferrara added.

A pulsar is the core of a massive star that exploded as a supernova. In this stellar remnant, also called a neutron star, the equivalent mass of half a million Earths is crushed into a magnetised, spinning ball.

The rotating magnetic field powers beams of radio waves, visible light, X-rays and gamma rays. If a beam happens to sweep across Earth, astronomers observe regular pulses of emission and classify the object as a pulsar.

The LOFAR discovery also hints at the potential to find a new population of ultra-fast pulsars.

Theorists say pulsars could rotate as fast as 72,000 revolutions per minute before breaking apart, yet the fastest spin known — by PSR J1748-2446ad, reaching nearly 43,000 revolutions per minute — is just 60 per cent of the theoretical maximum.

Perhaps pulsars with faster periods simply can’t form. But the gap between theory and observation may also result from the difficulty in detecting the fastest rotators.