Students discover flickering pulsar

Australian secondary school students have helped reveal strange, jittery behaviour in the pulsar PSR J1717-4054, located around 15,000 light years away in the direction of the constellation of Scorpius, as part of the PULSE@Parkes program. Their observations have led to a paper in the journal Monthly Notices of the Royal Astronomical Society.

Pulsars are highly magnetised balls of neutron matter the size of a small city, formed when stars with more than 10 times the mass of the Sun explode as supernovae and leave behind a compact remnant made of material far denser than ordinary matter. PSR J1717-4054 has long been observed as part of the PULSE@Parkes program, in which secondary school students use the CSIRO 64-m Parkes radio telescope in eastern Australia to observe pulsars.

Early observations of the pulsar, discovered in 1992, showed that its pulses of radio waves would ‘turn off’, vanishing for hours at a time. But student observations of the pulsar, which occurred 85 times between 2008 and this year, found that sometimes when the pulsar was ‘on’, it seemed to flicker.

“This prompted us to observe it for longer and with higher time resolution so that we could see individual pulses,” said CSIRO’s Dr Matthew Kerr, lead author of the new paper.

CSIRO astronomer Dr Matthew Kerr with students from Brigidine College in Sydney, using the CSIRO Parkes radio telescope to observe pulsars. Credit: Rob Hollow.

Thanks to the abundance of data gathered by the students, the pulsar’s properties have been well measured, including its position, spin-down rate, spectrum, polarisation characteristics and pulse broadening in the interstellar medium.

“The really weird thing is that it flickers in two different ways - it has quick blips on and off, skipping one or two pulses, and longer stutters, when 10 or more pulses go missing,” said Dr Kerr. “The stutters are new and there really aren’t any models that predict them.”

Dr Kerr said the pulsar’s behaviour is not “obviously abnormal - it looks like a run-of-the-mill pulsar”, yet while several pulsars are known to turn on and off, only two others show such varied behaviour as PSR J1717-4054.

“If this pulsar were a human heart, we’d be recommending a pacemaker,” he said.

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