Scientists have identified the second-fastest known pulsar, spinning at more than 42,000 revolutions per minute and located between 3,200 and 5,700 light-years away.
Scientists have identified the second-fastest known pulsar, spinning at more than 42,000 revolutions per minute and located between 3,200 and 5,700 light-years away. 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 no larger than Washington DC. 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. By following up on mysterious high-energy sources mapped out by NASA’s Fermi Gamma-ray Space Telescope, the Netherlands-based Low Frequency Array (LOFAR) radio telescope detected the pulsar.
The 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. At some point in this system’s history, matter began streaming from the companion and onto the pulsar, gradually raising its spin to 707 rotations a second, or more than 42,000 rpm, and greatly increasing its emissions. Eventually, the pulsar began evaporating its companion, and this process continues today.
Due to their similarity to spiders that consume their mates, systems like J0952 are called black widow or redback pulsars, depending on how much of the companion star remains. Most of the known systems of these types were found by following up Fermi unassociated sources. “LOFAR picked up pulses from J0952 at radio frequencies around 135 MHz, which is about 45 per cent lower than the lowest frequencies of conventional radio searches,” said Cees Bassa at the Netherlands Institute for Radio Astronomy (ASTRON). “We found that J0952 has a steep radio spectrum, which means its radio pulses fade out very quickly at higher frequencies. It would have been a challenge to find it without LOFAR,” said Bassa.
Theorists say that pulsars could rotate as fast as 72,000 rpm before breaking apart, yet the fastest spin known – by PSR J1748-2446ad, reaching nearly 43,000 rpm – is just 60 per cent of the theoretical maximum.