Scientists have discovered the brightest pulsar ever observed outside our galaxy, revealing the true identity of a distant luminous object previously mistaken for a distant galaxy.
What Is A Pulsar?
A pulsar is an incredibly dense neutron star that emits a beam of electromagnetic radiation from its poles.
Because this object rotates rapidly, high-energy radiation appears as short periodic pulses when viewed from anywhere in space. It’s like a space sign that can be seen periodically from afar.
Irish astrophysicist Jocelyn Bell has discovered more than 2,000 pulsars since their discovery in the 1960s, but the majority of these shiny rotating objects are inside our galaxy.
How Is Pulsar PSR J0523-7125 Different?
The newly discovered pulsar, designated PSR J0523-7125, is a much rarer extragalactic pulsar found beyond the Milky Way, in this case in the Large Magellanic Cloud.
PSR J0523-7125 was discovered in Australia by scientists using an ASKAP (Australian Square Kilometer Array Pathfinder) radio telescope array and could be discovered by scanning the sky for polarized pulsar emission, a technique that researchers compare to its astronomical equivalent of wearing polarized sunglasses.
“I didn’t expect to find a new pulsar, let alone the brightest. But with new telescopes like ASKAP and Sunglasses, it’s really possible.” According to researchers, PSR J0523-7125 is about 10 times brighter than any other extragalactic pulsar previously observed.
Why Was PSR J0523-7125 Not Known Before?
The answer lies with how pulsars are detected. Traditionally, the pulsar search procedure looks for periodic pulses, the beacon blinking effect, in which the pulsar emits radiation in short observable bursts.
But astronomers must find other ways to detect elusive pulsars that exhibit less predictable periodicities or other obscure properties of light. “Anomalous pulsars, such as short orbital binary systems or highly dispersed objects, are more difficult to detect,” the researchers write in a new paper.
What Are The Other Ways Of Finding These Hidden Pulsars?
One possible solution in these cases is to look for signs of circular polarization emanating from the object.
To date, only a few large-scale investigations have been able to document radiation in circularly polarized light, one of which has been carried out at the ASKAP facility.
In a research project called VAST, the researchers filtered ASKAP data to find variable, transient sources of luminescence events.
They identified PSR J0523-7125 as a pulsar, and subsequent observations with the MeerKAT radio telescope in South Africa and CSIRO’s Parkes Observatory in Australia confirmed the discovery.
“We should expect to find more pulsars with this technique,” explains University of Sydney lead author and astrophysicist Tara Murphy.
“For the first time, we have been able to systematically and routinely explore the polarity of a pulsar.”
According to researchers, PSR J0523-7125 exceeds previous theoretical luminosity limits for bright pulsars expected in the Large Magellanic Cloud, showing that their brightness is equivalent to that of objects observed in our galaxy.
Extragalactic pulsars are still relatively rare, but as large-scale radio continuum surveys and the availability of future telescopes increase, the ability to detect pulsars and other types of pulsars that are difficult to detect with conventional methods should increase in the future.
An example is the upcoming Square Kilometer Array project under construction in South Africa.
“In the era of square-kilometer arrays, as equipment improves, instantaneous wide field of view and high sensitivity will become much more common, detecting numerous radio sources across the sky,” the researchers explain.
“The rise of advanced next-generation radio telescopes and large-scale multi-wavelength irradiation will bring large amounts of data with high sensitivity and resolution, and we will have an unprecedented ability to identify more pulsars.”