February 26, 2024

Astronomers have detected a radio signal in our galaxy that is beeping for a few minutes every 21 minutes and has been going on for at least 35 years. Such strange signals would not fit the requirements of any known object without major modifications to current physics.

The signal was first detected by the Murchison Widefield Array (MWA), a radio telescope spanning the Western Australian outback. It has been named GPM J1839-10 and has been traced to the constellation Scutum, about 15,000 light-years from Earth.

Repeated radio bursts were detected in MWA data between July and September 2022 and subsequently confirmed by various other telescopes around the world. Burst durations range from 30 seconds to 5 minutes, with bursts occurring every 21 minutes like clockwork. This makes it the longest repeating radio source ever discovered in the universe.

The lead candidate, the team says, is an ultra-long-period magnetar. These compact objects are types of neutron stars that have exceptionally strong magnetic fields that emit periodic radio signals as they spin.

The problem is, most of them spin so fast that their radio bursts only last a few milliseconds or a second or two at most, and repeat over a few minutes at most. Based on what we know of magnetar physics, it’s impossible for a magnetar to spin so slowly that its outbursts last five minutes, and the full cycle takes more than 20 minutes to repeat.

“Assuming it’s a magnetar, there’s no way the object could be generating radio waves,” said lead author Dr Natasha Hurley-Walker. “But we’re seeing them. Whatever the mechanism behind this is, it’s remarkable.”

Adding to the mystery is the fact that GPM J1839-10 has been active for much longer than any other known magnetar. Most radio waves go through a phase of emitting radio waves that lasts only a few months to a few years before fading away, but that phase seems to have lasted about 35 years. The researchers examined existing data from multiple radio telescopes at the same coordinates and found that the signal had been bursting since at least 1988.

Most intriguingly, the detection is part of a series of new observations of magnetar-like objects that appear to defy the usual rules. In 2021, the same team found a similar signal, emitting radio bursts that lasted one minute every 18 minutes, but this lasted only three months before disappearing.

Thankfully, a year after its first discovery, GPM J1839-10 is still going strong. This allowed astronomers to continue observing and hopefully find an explanation. Given these similarities, it may be related to another space mystery – fast radio bursts.

The study was published in the journal nature. The team describes the work in the video below.

ultra long period magnetar

source: ICRAR, dialogue