Telescope dons 'sunglasses' to find brightest ever pulsar

A new observation technique has helped University scientists uncover the brightest extragalactic pulsar known, and it could even be the most luminous one ever found.

Since the Nobel Prize-winning discovery of pulsars in 1967, these unusual stars – themselves remnants of massive stars – have been an object of fascination. 

Though 10 times brighter than any other pulsar detected outside our Galaxy, this new pulsar had not been seen before.

Led by the University of Sydney, an international research team used the ASKAP radio telescope, owned and operated by Australia’s national science agency, CSIRO, to find the pulsar. They applied a new and unusual method of seeking out pulsars – using the astronomical equivalent of ‘sunglasses’ to capture polarised light.

Lead researcher on the paper that describes the findings, published by the Astrophysics Journal, is University of Sydney PhD candidate and CSIRO researcher Yuanming Wang. She said this pulsar was an amazing surprise: “I didn’t expect to find a new pulsar, let alone the brightest. But with the new telescopes we now have access to, like ASKAP and its sunglasses, it really is possible.”  

Professor Tara Murphy, from the Sydney Institute for Astronomy at the University of Sydney, leads the team who saw the first hints of this unusual pulsar in the ASKAP data and confirmed its existence with the South African Radio Astronomy Observatory’s MeerKAT radio telescope. She said we should expect to find more pulsars using this technique.

“This is the first time we have been able to search for a pulsar’s polarisation in a systematic and routine way. This pulsar doesn’t disappear from the sky for long, like most other pulsars, which is why it was missed in previous studies despite its astounding brightness.”

Professor Elaine Sadler, Chief Scientist of CSIRO’s Australia Telescope National Facility, which includes ASKAP and two other telescopes used in the study, said it is incredible that the first pulsar they found using this technique is an extreme one.

“This speaks to all the great things we can expect from our researchers and telescopes as they constantly find new ways to answer some of our biggest questions.”

A pulsar is a rapidly rotating neutron star that emits two beams of polarised radio light. As the beams flash across space, they create a unique timing and polarisation signature. Traditional methods of finding pulsars look for this flickering in telescope data but can miss those that are too fast or too slow. By looking instead for light that is polarised, pulsars outside the standard timing range can be found.

Before now, the bright spot in the radio data was overlooked as a distant galaxy.

Pulsars are currently being researched for their potential in helping random number generation and guidance systems for spacecraft. The more we find, the more options we have for future applications.

Declaration: This research was supported by the China Scholarship Council; the Australian Research Council (grant DP190100561); NSF grant AST-1816492; the H2020 ERC Consolidator Grant (SGR2017-1383 and PGC2018-095512-B-I00); an ARC Future Fellowship (FT 190100155); the National Institute for Astrophysics; the Max-Planck Society; the Ministero degli A_ari Esteri e della Cooperazione Internazionale – Direzione Generale per la Promozione del Sistema Paese - Progetto di Grande Rilevanza (ZA18GR02); NSERC Discovery Grants RGPIN-2016-06569 and RGPIN-2021-0400; and the Sydney Informatics Hub (SIH), a core research facility at the University of Sydney.

Hero image: 15 of the MeerKAT radio telescope’s 64 dishes are lit up by the rising Sun in the Karoo, South Africa. MeerKAT is owned and operated by the South African Radio Astronomy Observatory (SARAO). Credit: SARAO.