Science

Astronomers have discovered the brightest intergalactic pulsar outside the Milky Way

A new study suggests that the newly discovered pulsar is more than 10 times brighter than any other rapidly rotating stars we know of.

Pulsars are rapidly rotating neutron stars or dense cores of material left over from supernova explosions that emit radio pulses at regular intervals. The newly discovered pulsar, dubbed PSR J0523-7125, is also relatively close by galactic standards. It is located in the Large Magellanic Cloud, a satellite galaxy of the Milky Way, about 160,000 light-years from Earth.

“This was unexpected and exciting as there were no known pulsars or dwarf stars at this location,” the study authors wrote in an article in The Conversation. “We decided that the object should be something new. We have observed it with many different telescopes at different wavelengths to try and solve the mystery. Both the approval and the study were led by Yuanming Wang, a doctoral student at the University of Sydney in Australia.

On the subject: 50 years ago, Jocelyn Bell discovered pulsars and changed our understanding of the universe

Although scientists have discovered more than 3,300 radio pulsars since the 1960s, only 1% of them are known outside the galaxy. Moreover, many of the discoveries have been made with a single radio telescope: Australia’s Parkes Observatory, which is operated by the Australian Government’s Scientific and Industrial Research Organization (CSIRO). (This telescope is also famous for capturing footage of Apollo 11’s footsteps on the Moon.)

PSR J0523-7125 eluded detection because its beam was wider than usual, making it difficult to find, although there are at least 30 known pulsars outside our galaxy, mostly in the Large and Small Magellanic Clouds in the general region of the sky. .

However, the authors found it using polarization data. Polarization refers to the way electromagnetic light waves rotate in a circle as the waves travel through space. Although rare, these signals can come from pulsars and other objects with strong magnetic fields.

The Large Magellanic Cloud, where the pulsar was discovered. (Image credit: CTIO/NOIRLab/NSF/AURA/SMASH/D. Nidever/Travis Rector/Mahdi Zamani/Davide de Martin)

Since the human eye cannot see polarized light, the authors turned to the Australian Telescope CSIRO National Facility (ASKAP). The observatory “has the equivalent of polarized sunglasses that can recognize circularly polarized events,” the authors write.

And that’s when a new pulsar appeared, they said. “While browsing data from our ASKAP Variables and Slow Transients (VAST) survey, an undergraduate student noticed a circularly polarized object near the center of the Large Magellanic Cloud,” the study authors say. “Moreover, this object changed brightness over the course of several months: another very unusual property that made it unique.”

Pulsar PSR J0523-7125 is visible in MeerKAT images. (Image credit: Yuanming Wang (Uni Sydney) / ASKAP VAST / MeerKAT)

The authors attempted to confirm the find with the Parkes Observatory, the Neil Gerels Swift Space Observatory (X-ray) and the Gemini Telescope in Chile (Infrared). After none of these observatories found the object, the team turned to MeerKAT, a radio telescope that had recently started operating in South Africa.

This time they hit the jackpot. “Observations with MeerKAT showed that the source is indeed the new pulsar PSR J0523-7125, which rotates at a speed of about three revolutions per second,” the authors say.

The core of the MeerKAT radio telescope array. (Image credit: South African Radio Astronomy Observatory)

They noted that combining the capabilities of MeerKAT and ASKAP could lead to more pulsar discoveries and that the square kilometer array should also be useful once this observatory, the world’s largest radio telescope, is fully built.

“We will need to find more of them before we can truly understand pulsars within the framework of modern physics,” the authors say. “This discovery is just the beginning.”

The study, based on the study, was published May 2 in The Astrophysical Journal.

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