Unknown objects at the heart of the Milky Way are beaming radio signals, then mysteriously disappearing
The radio telescope at the Parkes Observatory at sunset near the town of Parkes, Australia, July 15, 2019.
Stefica Nicol Bikes/ReutersZiteng Wang found a needle in an astronomical haystack.
Wang, a physics PhD student at the University of Sydney, was combing through data from Australia's ASKAP radio telescope in late 2020. His research team had detected 2 million objects with the telescope and was classifying each one.
The computer identified most of the stars, and the stage of life or death they were in. It picked out telltale signs of a pulsar (a rapidly rotating dead star), for example, or a supernova explosion. But one object in the center of our galaxy stumped the computer and the researchers.
An artist's impression of the mysterious radio signal coming from the center of the Milky Way.
Sebastian Zentilomo/University of Sydney
The object emitted powerful radio waves throughout 2020 — six signals over nine months. Its irregular pattern and polarized radio emissions didn't look like anything the researchers had seen before.
Even stranger, they couldn't find the object in X-ray, visible, or infrared light. They lost the radio signal, too, despite listening for months with two different radio telescopes.
It reappeared suddenly, about a year after they first detected it, but within a day, it was gone again.
"Unfortunately, we don't quite know what behaves like that," Tara Murphy, a professor at the University of Sydney who led Wang's research team, told Insider.
It was becoming clear that this was no ordinary dead star, like the other 2 million objects in their survey.
"That's when we started getting excited," Murphy said.
The team sent their data to other radio astronomers, asking for theories. Bit by bit, they confirmed that no one had ever detected anything like it before.
The researchers' conclusion: The discovery could belong to an obscure category of mysterious signals coming from the core of the Milky Way, known as "galactic center radio transients" (GCRTs). Before Wang's discovery, only three such objects had ever been identified.
The name GCRT is a "position holder," Murphy said, "while we actually try and figure out what they are."
The central region of the Milky Way galaxy, as imaged by the Hubble Space Telescope, the Spitzer Space Telescope, and the Chandra X-ray Observatory in 2009.
Murphy is "100% confident" that the signals aren't coming from aliens, because technological signals would cover a much narrower range of frequencies, like humans' broadcast radios do.
GCRTs have been a mystery for decades now. Nobody knows what type of star would make those unique signals, and each GCRT is different, leading researchers to believe the four signals are not coming from the same type of object.
Any new discovery "adds to the full body of knowledge that either cements what we already know, or adds to it, or really could lead to revolutionary new understandings," Scott Hyman, who led the research efforts that discovered the three prior GCRTs, told Insider. "Whether these objects fall into those categories, we don't know. We don't know enough about them."