Radio waves

Mysterious radio waves from an unknown object at the center of the galaxy

  • Astronomers have detected mysterious radio waves coming from the center of the galaxy that vary widely and seem to die out randomly.
  • The origin of the waves is unknown, so they suggest the existence of a new type of celestial object.
  • The signal does not resemble that which comes from stars, planets or even dead stars.

Mysterious radio waves emanate from the heart of our galaxy, and astronomers don’t know what makes them.

All celestial objects emit radio waves – planets, stars, dead stars and even asteroids. But researchers at the University of Sydney have recently detected radio signals that don’t match any known type. The waves, originating near the center of the Milky Way, do not appear to originate from any kind of star, planet or space rock that scientists have ever seen.

Even stranger, the strength of this signal rose and fell dramatically in just a few months. Most objects in the galaxy, on the other hand, don’t change much from year to year – and so neither do their radio waves.

“The signal turns on and off seemingly randomly. We’ve never seen anything like this,” said Ziteng Wang, lead author of the new study and a PhD student in physics at the University of Sydney. Press release.

An article describing the discovery was published Tuesday in The Astrophysical Journals. In it, Wang and his co-authors concluded that the mysterious source of this radio signal “could represent part of a new class of objects.”

Radio signal disappeared for months, suddenly reappeared, then disappeared again

radio wave animation shows distant bright light sending intermittent spirals towards earth

Artist’s impression of the mysterious radio signal from the center of the Milky Way.

Sebastian Zentilomo/University of Sydney

Whatever mysterious object is responsible for this phenomenon, it emitted strong radio waves for most of 2020. Researchers detected six signals over nine months, using the ASKAP radio telescope in western Australia.

After that, the team tried to find the object in visible light, but they came back empty-handed. They also couldn’t find it in X-rays or infrared light.

So they went back to radio waves, first using Australia’s Parkes radio telescope, but they lost the signal source and couldn’t detect anything for a while. Then they turned to a different radio telescope – the MeerKAT observatory in South Africa – and observed the area for 15 minutes every few weeks.

Eventually they picked up the radio signal once more, but it disappeared in a single day. It was strange, since the six signals they had picked up with ASKAP had each lasted for weeks.

“This object was unique in that it started out invisible, became bright, faded, then reappeared. This behavior was extraordinary,” said Tara Murphy, a professor at the University of Sydney and thesis supervisor of Wang, in the statement.

Murphy and Wang aren’t talking about visual brightness – a “bright” radio signal is just a strong signal.

“The brightness of the object also varies significantly, by a factor of 100,” Wang said in the statement.

In an email, Murphy told Insider “that’s part of what makes it unusual.”

“Objects that are hot (e.g. stars) usually emit visible light, so we ruled out a normal star as one of the possible interpretations for this object,” she wrote. “It could be a very, very cool star that’s too faint to detect visible light but has bright radio flares.”

The mysterious radio signal shares some traits with signals from a class of objects called “Galactic Center radio transients” that were discovered in the 2000s. But researchers don’t know much about these objects either, except that they emit low-frequency, highly polarized radio waves with no detectable X-rays. Yet the new signal has properties that do not match those of radio transients.

“We don’t really understand these sources, anyway, so that adds to the mystery,” Wang’s co-supervisor, David Kaplan of the University of Wisconsin-Milwaukee, said in the statement.