Mysterious object ‘unlike anything’ seen before, discovered in Milky Way

Astronomers have discovered a mysterious, flickering object in the Milky Way that belches enormous amounts of energy toward Earth three times an hour.

This strangely powerful object — located about 4,000 light-years from the sun — is unlike any cosmic structure ever observed, researchers wrote in a study published Jan. 26 in the journal Nature

The team who discovered it think it could be a neutron star or a white dwarf — collapsed cores of stars — with an ultra-powerful magnetic field.

Spinning around in space, the strange object sends out a beam of radiation that crosses our line of sight, and for a minute in every twenty, is one of the brightest radio sources in the sky.

“This object was appearing and disappearing over a few hours during our observations. That was completely unexpected,” lead study author Natasha Hurley-Walker, a radio astronomer at Curtin University in Bentley, Australia, said in a statement. “It was kind of spooky for an astronomer because there’s nothing known in the sky that does that.”

“And it’s really quite close to us — about 4000 lightyears away. It’s in our galactic backyard.”

Last light of a dying star

Objects that turn on and off in the Universe aren’t new to astronomers — they call them ‘transients’.

Transients typically come in two varieties. “Slow transients” can appear over the course of a few days, then disappear after several months. These include supernovas — which blaze brightly as dying stars shed their outer atmospheres in violent explosions, then gradually dim as the stellar leftovers drop in temperature.

Then, there are “fast transients,” which flicker on and off every few milliseconds. These include objects like pulsars — neutron stars which rotate incredibly rapidly while flashing with bright radio emissions generated by the dead star’s magnetic field. 

The authors of the new study were looking for transients like these using the Murchison Widefield Array (MWA) radio telescope in the Australian outback, when they discovered the object named ‘GLEAM-X J162759.5-523504.3’ . The on-off blinking is too fast to be a supernova and too slow to be a pulsar; GLEAM’s one-minute-long brightening pattern defies explanation, the researchers said.

An analysis of the object showed that it was incredibly bright but smaller than Earth’s sun. GLEAM’s radio emissions were also highly-polarized (that is, their light waves only vibrate on a single plane), suggesting they were generated by an extremely powerful magnetic field, according to the study authors.

Dr Hurley-Walker said the observations match a predicted astrophysical object called an ‘ultra-long period magnetar’.

“It’s a type of slowly spinning neutron star that has been predicted to exist theoretically,” she said.

“But nobody expected to directly detect one like this because we didn’t expect them to be so bright.

“Somehow it’s converting magnetic energy to radio waves much more effectively than anything we’ve seen before.”

Dr Hurley-Walker is now monitoring the object with the MWA to see if it switches back on.

“If it does, there are telescopes across the Southern Hemisphere and even in orbit that can point straight to it,” she said.

Dr Hurley-Walker plans to search for more of these unusual objects in the vast archives of the MWA.

“More detections will tell astronomers whether this was a rare one-off event or a vast new population we’d never noticed before,” she said.

MWA Director Professor Steven Tingay said the telescope is a precursor instrument for the Square Kilometre Array — a global initiative to build the world’s largest radio telescopes in Western Australia and South Africa.

“Key to finding this object, and studying its detailed properties, is the fact that we have been able to collect and store all the data the MWA produces for almost the last decade at the Pawsey Research Supercomputing Centre. Being able to look back through such a massive dataset when you find an object is pretty unique in astronomy,” he said.

“There are, no doubt, many more gems to be discovered by the MWA and the SKA in coming years.”

The Murchison Widefield Array is located on the Murchison Radio-astronomy Observatory in Western Australia. The observatory is managed by CSIRO, Australia’s national science agency, and was established with the support of the Australian and Western Australian Governments. We acknowledge the Wajarri Yamatji as the traditional owners of the observatory site.

The Pawsey Supercomputing Research Centre in Perth-a Tier 1 publicly funded national supercomputing facility-helped store and process the MWA observations used in this research.

Shanghai Astronomical Observatory (SHAO) is a member of the MWA. China’s SKA Regional Centre Prototype, funded by the Ministry of Science and Technology of China and the Chinese Academy of Sciences, is hosted by SHAO and contributed to processing the MWA observations used in this research.