Most pulsars rotate once every couple of seconds, but one pulsar completes a revolution just once every 76 seconds
Artist’s impression of a pulsar
Shutterstock/NASA images
A pulsar that is rotating just once every 76 seconds raises questions about how long these star remnants can remain active.
When a giant star explodes as a supernova, it can leave behind a dense core in the form of a neutron star. If this core is highly magnetised and spinning rapidly, it can send out regular pulses of radio emissions, and is known as a pulsar.
Manisha Caleb at the University of Manchester, UK, and her colleagues have discovered a particularly odd pulsar called PSR J0901-4046 using observations from the MeerKAT radio telescope in South Africa.
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Located about 1000 light years from Earth, it rotates far slower than any known active pulsar, sending out a regular 300-millisecond-long pulse every 76 seconds.
“This is a very unusual type of radio-emitting neutron star,” says Caleb. “It resides in what we call the ‘neutron star graveyard’ where we don’t expect pulses to emit. It’s like a zombie star.”
Pulsars typically spin once every 0.25 to 2 seconds, but as they age, they lose energy and spin more slowly. Eventually, they stop sending out pulses and become regular neutron stars in a stellar graveyard. The boundary that this occurs at is known as the “death line”.
The discovery more than doubles the previous record for the slowest-spinning pulsar, which took 23 seconds to rotate. So our understanding of where the death line begins “may need to be revisited”, says Caleb. “Sources in the neutron star graveyard can still emit.”
The fact that the star is still a pulsar challenges some theoretical models, says Cole Miller at the University of Maryland, College Park.
Journal reference: Nature Astronomy, DOI: 10.1038/s41550-022-01688-x
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