Astronomers Searching for Planets Detect Radio Signals From Distant Stars

Astronomers have used the world's most powerful radio antenna to discover red dwarf stars that are blasting out radio waves, indicating they could harbor hidden worlds.

The discovery came as the team, led by the University of Queensland, Australia's Dr. Benjamin Pope, was searching for planets beyond the solar system—exoplanets—using the Low-Frequency Array (LOFAR) radio telescope located in the Netherlands.

"We've discovered signals from 19 distant red dwarf stars, four of which are best explained by the existence of planets orbiting them," Pope said in a press release from the University of Queensland. "This discovery is an important step for radio astronomy and could potentially lead to the discovery of planets throughout the galaxy."

Astronomers have known for some time that planets within the solar system emit powerful radio waves when their magnetic fields are bombarded by a stream of charged particles released from the upper atmosphere of the sun.

This effect can be seen on our planet when solar winds strike the Earth's magnetosphere and create spectacular atmospheric displays called the Northern and Southern Lights.

Northern Lights
Earth's aurora as seen from the International Space Station. Astronomers believe that radio emissions from distant red dwarfs could be the result of the same magnetic interactions that cause the aurora on Earth, but on hidden worlds. NASA

The team focused on looking for radio emissions from red dwarfs, which are around 8 percent to 60 percent less massive than the sun and are characterized by intense magnetic activity. Just as happens with our star, this magnetic activity drives outbursts like stellar flares and radio emissions.

This understanding of stars was challenged when magnetically inactive stars were discovered that still emit powerful radio signals.

This leads Leiden University of the Netherlands and ASTRON researcher Dr. Joseph Callingham to believe that radio signals from these red dwarfs are coming from the magnetic connection between the stars and unseen planets orbiting them.

"Our own Earth has aurorae, commonly recognized here as the Northern and Southern lights, that also emit powerful radio waves—this is from the interaction of the planet's magnetic field with the solar wind," Callingham said.

The Leiden University researcher went on to point out that the aurorae of Jupiter are much stronger than those of Earth. This is because its volcanic moon Io is blasting material out into space, filling Jupiter's environment with particles that drive unusually powerful aurorae.

"Our model for this radio emission from our stars is a scaled-up version of Jupiter and Io, with a planet enveloped in the magnetic field of a star, feeding material into vast currents that similarly power bright aurorae," Callingham continued. "It's a spectacle that has attracted our attention from light-years away."

Calligham is the lead author of a paper in Nature Astronomy that details the team's theory. The next step for the researchers is to conclusively confirm the existence of the exoplanets they suspect are orbiting these red dwarfs and blasting out radio waves.

"We can't be 100 percent sure that the four stars we think have planets are indeed planet hosts, but we can say that a planet-star interaction is the best explanation for what we're seeing," Pope said. "Follow-up observations have ruled out planets more massive than Earth, but there's nothing to say that a smaller planet wouldn't do this."

An Exoplanet Around a Red Dwarf Star
A illustration shows what an exoplanet may look like as it orbits a red dwarf. Researchers have discovered that radio signals from distant red dwarfs could indicate hidden worlds. L. Calçada/ESO