House: Thriller radio waves are coming from the centre of the galaxy

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Illustration of radio waves coming from the galactic centre

Sebastian Zentilomo

Strange radio signals are coming from the direction of the centre of the galaxy, and we’re not sure what is emitting them. They turn on and off seemingly at random, and their source must be unlike anything else we’ve seen before.

The source of this radiation has been nicknamed “Andy’s object” after Ziteng Wang at the University of Sydney in Australia, who goes by Andy and first discovered the radio waves. He and his colleagues spotted these emissions 6 times in 2020 using the Australian Square Kilometre Array Pathfinder radio telescope, and took further observations with the MeerKAT radio telescope in South Africa.

The researchers found that it occasionally flared for up to a few weeks but was dark most of the time. When it finally lit up again in February, several months after the initial detection, they pointed some of the most powerful non-radio telescopes we have at it and saw nothing. “We’ve looked at every other wavelength we can, all the way from the infrared to optical to X-rays, and we see nothing, so it doesn’t seem to be consistent with any kind of star that we understand,” says David Kaplan at the University of Wisconsin-Milwaukee, who was part of the research team.

The fact that it wasn’t visible in any of the other wavelengths of light ruled out several possible explanations for this object, including normal stars and magnetars, which are neutron stars with powerful magnetic fields.

Whatever Andy’s object is, the polarisation of the radio waves coming from it indicates that it probably has a strong magnetic field. The facts that during flares its brightness varied by up to a factor of 100 and that those flares faded extraordinarily quickly – as fast as a single day – also hint that it is probably a small object.

But no astronomical object we know of fits all of those strange traits. “It’s an interesting object that has confounded any attempt we have to explain it,” says Kaplan. “It could turn out to be part of a known class of objects, just a weird example, but that’ll push the boundaries of how we think those classes behave.”

Journal reference: The Astrophysical Journal, DOI: 10.3847/1538-4357/ac2360

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