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Students astonished by stuttering star

Last Updated on Wednesday, 01 October 2014 14:12
Published on Wednesday, 01 October 2014 05:00

Secondary school students in Australia have helped reveal weird, jittery behaviour in a pulsar called PSR J1717−4054. The results of their observations and of follow-up studies are published online today in the journal Monthly Notices of the Royal Astronomical Society (MNRAS).

Pulsars are super-dense, highly magnetised balls of ‘neutron matter’ the size of a small city. They form when a star with more than 10 times the mass of our Sun explodes as a supernova, leaving behind a compact remnant made of material far denser than ordinary matter. The name pulsar is given to these objects because they spin and emit pulses of radio waves.

Discovered in 1992, PSR J1717−4054 is around 15,000 light years away in the direction of the constellation of Scorpius (the Scorpion). Early observations showed that its pulses would 'turn off', vanishing for hours at a time.

Brigidine SOCMatthew 5621 smallCSIRO astronomer Dr Matthew Kerr with students from Brigidine College, in Sydney, Australia, using the CSIRO Parkes radio telescope to observe pulsars. Credit: Rob Hollow. Click for a full resolution imageThis intriguing behaviour made it a favourite in the PULSE@Parkes programme, in which secondary school students use the Commonwealth Scientific and Industrial Research Organisation (CSIRO) 64-metre Parkes radio telescope in eastern Australia to observe pulsars. Students observed the pulsar 85 times between 2008 and this year.

"When the students looked at it, it was generally on or off.  But sometimes, when it 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.

"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 ten or more pulses go missing.  The stutters are new and there really aren't any models that predict them," he said.

"If this pulsar were a human heart, we would be recommending a pacemaker."

Thanks to the abundance of data gathered by the students, the pulsar’s parameters have been well measured. "It’s not obviously abnormal – it looks like a run-of-the-mill pulsar," Dr Kerr said. While several pulsars are known to 'null' – turn on and off – only two others show such varied behaviour as PSR J1717−4054.

More than 1000 students have taken part in Pulse@PARKES. Today’s MNRAS paper is the first of many publications that will arise from the programme.


Further information

The new work appears in M. Kerr et al., "Three Discrete Nulling Timescales of PSR J1717−4054", Monthly Notices of the Royal Astronomical Society, vol. 445, pp. 320-329, 2014, published by Oxford University Press. A preprint of the paper is available on the arXiv server.


Science / media contact

Dr Matthew Kerr
CSIRO Astronomy and Space Science (in Sydney, Australia)
Tel: +61 2 9372 4442
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Image and caption

An image of the students is available for download.

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


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