An analysis of observational data from the Murchison Widefield Array telescope led to the discovery of a mysterious object that flashes brightly in the radio range once every 18 minutes. This behavior of radio signals has not been observed from any previous source, and, according to astronomers, it is consistent with the theoretically predicted “ultra-long period magnetars”.  

A strange object has been emitting radio signals once every 18 minutes – is it the first ultra-long period magnetar?

“As it rotates, this strange object emits a beam that, when it crosses our line of sight for a minute, makes it one of the brightest radio sources in the sky. It was a little creepy to watch because we had never seen anything like it before.”

The mysterious object, which received the designation GLEAM-X J162759.5-523504.3, is located at a distance of about four thousand light-years from Earth in the direction of the constellation Angle. It is much smaller than the Sun and has an extremely strong magnetic field. From January to March 2018, 71 impulses were recorded from the source during the observation campaign.

Artistic representation of a magnetar with an ultra-long period – a potential source of repetitive pulses of radio waves/signals. Credit: ICRAR

Transients – objects that appear once or periodically first and then disappear in the sky – are quite common in the Universe and are not something new for astronomers.

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Slow transients, such as supernovae, can gradually increase in brightness over several days, then dim and disappear after months.

Fast transients, such as pulsars, flash on and off within milliseconds or seconds. However, the behavior of GLEAM-X J162759.5-523504.3 does not match any previously observed astrophysical object.

“The observations are best explained by the fact that we are looking at a magnetar with an ultra-long period – a slowly rotating neutron star, the existence of which was theoretically predicted. In some as yet inexplicable way, it converts magnetic energy into radio waves much more efficiently than any source known to us.”

Curiously, magnetars have been considered the primary candidate for the source of fast radio bursts, another phenomenon like the current radio signals that remains unsolved.

Part of the Murchison Widefield Array observatory. Credit: Pete Wheeler/ICRAR

What are fast radio bursts?

If you somehow missed the hundreds of fast radio burst news over the past few years, these are bright pulses of radio signals that last milliseconds and are recorded at frequencies of 0.1–8 gigahertz.

They were first discovered in 2007, and since then they have remained one of the main unresolved problems of modern astrophysics.

In particular, the mechanism of burst generation has not yet been unambiguously established (it may be associated with magnetars), and it is also unclear why some burst sources appear only once, while others generate repeated bursts.

To understand the nature of the sources of repetitive fast radio bursts, scientists need to look for the galaxies in which they are located and determine their properties.

To date, only four cases of reliable identification of the source of repeated bursts with a particular galaxy are known. In all cases, the galaxies are characterized by a low or moderate rate of star formation, some have spiral arms. The burst sources themselves were located in different regions of galaxies, for example, in globular clusters and star-forming regions.

Sources:

• Hurley-Walker, N., & Wheeler, P. (2022, January 26). Bizarre radio signal repeating every 18 minutes discovered in milky way. New Atlas.

• Hurley-Walker, N., Zhang, X., Bahramian, A., McSweeney, S. J., O’Doherty, T. N., Hancock, P. J., Morgan, J. S., Anderson, G. E., Heald, G. H., & Galvin, T. J. (2022, January 26). A radio transient with unusually slow periodic emission. Nature News.

• ICRAR. (2022, January 26). Mysterious object unlike anything astronomers have seen before.

• Starr, M. (n.d.). Astronomers detect strange signals we’ve never seen before in our cosmic vicinity. ScienceAlert.

• Weule, G. (2022, January 26). ‘very, very spooky’: Astronomers discover mysterious object emitting pulses of energy. ABC News.

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