For decades, astronomers have been listening to the universe: the faint crackle of radio waves, the rhythmic pulse of neutron stars, and the silent signatures of black holes. But in 2018, something unlike anything seen before caught their attention: a steady, rhythmic “heartbeat” coming from the depths of space, repeating every few minutes. The signal, first picked up by radio telescopes in Western Australia, didn’t behave like anything scientists had catalogued before. It wasn’t the rapid spin of a pulsar or the flare of a distant star. Instead, it flashed with uncanny regularity, a two-minute burst of radio energy, followed by a long silence, then another pulse, like the slow, patient beat of some cosmic heart. Scroll down to read more.
The discovery
The object was catalogued as GLEAM-X J162759.5-523504.3, and its strange pattern was first noticed by a team of astronomers using the Murchison Widefield Array (MWA), a powerful radio telescope operated by Curtin University and the International Centre for Radio Astronomy Research (ICRAR) in Australia.Dr Natasha Hurley-Walker, an astrophysicist at Curtin University and the lead author of the discovery paper published in Nature (2022), described it as one of the most unusual things ever seen in the sky. Most radio sources flicker unpredictably, but this one turned on for about a minute every twenty minutes, like clockwork.The first data showed a pulse every 18.18 minutes, recorded during observations in early 2018. Follow-up research and new detections in 2023 revealed another object, or possibly the same one, with a slightly slower and more stable rhythm of 22 minutes between bursts, hence the description as a cosmic “heartbeat”.
I visualize immense, ethereal waves of pulsating radio energy rippling through the vast, dark expanse of space, creating a cosmic heartbeat.
The detection stunned researchers. Hurley-Walker noted that the object was unlike any known astrophysical phenomenon, adding that its slow, intense repetition challenges existing understanding of neutron stars and magnetic fields.
Not a pulsar, not a magnetar
Normally, periodic signals in space are associated with pulsars, rapidly spinning neutron stars that emit radio beams as they rotate, much like cosmic lighthouses. Their pulses usually last milliseconds or seconds. Some magnetars, neutron stars with extremely strong magnetic fields, also emit bursts of radio and X-ray energy , but never at such slow intervals.
To put the mystery in perspective, typical pulsars spin dozens to hundreds of times per second. Even the slowest known pulsars rotate roughly once every 10 seconds. A 22-minute period is far beyond the physical limit of known neutron star rotation speeds.Dr Hurley-Walker explained in an interview with MIT News that the object appears to fall between known categories and could represent an ultra-long-period magnetar, a theoretical type of star never confirmed before.If true, this would mark the first observational evidence of such a star: a slowly rotating, highly magnetised neutron star that manages to emit powerful radio waves long after most magnetars fade away.
The heartbeat that refused to fade
Archival radio data suggest the signal region may have shown faint activity in past decades, but no continuous emission has been confirmed. What scientists do know is that the object’s 2018 signal remained stable during several months of observation, far longer than typical magnetar bursts, which usually fade within years.That longevity is extraordinary. Ordinary magnetars lose energy quickly, usually dimming after short outbursts. For this source to remain detectable for months, and possibly return years later, it must be powered by an energy mechanism scientists have yet to fully understand.Professor David Kaplan, co-author of the study, noted that the object appears to defy established laws of astrophysics, shining unusually bright and repeating its signal with striking precision.
What could it be?
There are a few leading theories:
An ultra-long-period magnetar: The most likely explanation is a rare neutron star with an extraordinarily slow spin and a still-active magnetic field.A white dwarf pulsar: Some researchers suggest it could be a highly magnetised white dwarf, the remnant of a dying star slightly less massive than those that form neutron stars.A binary system: Another possibility is that it’s part of a binary pair, two stars orbiting each other, producing periodic bursts as one eclipses or feeds off the other.However, none of these models fully explain its consistency and power. The bursts are so intense they can be detected from 15,000 light-years away, in the direction of the Scorpius constellation.
A heartbeat from the unknown
The discovery was detailed in Nature (Hurley-Walker et al., 2022) and later featured in official releases by the International Centre for Radio Astronomy Research and Curtin University. Subsequent studies confirmed a 22-minute pulse cycle in 2023 using long-term data from multiple radio arrays.What makes it remarkable is its predictability; every 22 minutes, a clean, bright flash cuts across the cosmic noise, as if a clock were ticking somewhere in the dark.Hurley-Walker explained that the object is what astronomers call a “transient”, something that turns on and off in the radio sky, but unlike any seen before. It pulses slowly, regularly, and with unusual power, as if the universe has found a rhythm not yet understood.
Looking ahead
Astronomers worldwide are now tracking the object, hoping new telescopes, particularly the upcoming Square Kilometre Array (SKA), will capture more data. If more such “heartbeat” sources are found, it could mean an entirely new class of stellar objects.Until then, GLEAM-X J162759.5-523504.3 remains a riddle pulsing steadily in the dark, a 22-minute metronome marking time in deep space, far beyond the reach of our understanding. In the cold silence of the universe, something is beating, and it has been for years.