Radio signals from distant stars suggest hidden planets

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Scientists have found stars that emit radio waves unexpectedly using the most powerful antenna radio radio, which could indicate the existence of hidden worlds.

Dr. Benjamin Pope, University of Queensland, and his colleagues from the Dutch national observatory ASTRON have been looking for planets with the most powerful radio telescope Low Frequency Array in the world (LOFAR), which is located in the Netherlands.

Pope stated that signals were discovered from 19 red dwarf stars. Four of these signals can be best explained by planets orbiting them.

"We have known for a long time that the magnetic fields of the planets in our solar system emit radio waves. However, radio signals from other planets within our solar system were not yet detected.

"This discovery is an important milestone in radio astronomy, and could lead to the discovery planets across the galaxy."

Astronomers could only detect the nearest stars using steady radio emission. Everything else in the radio sky was either interstellar gases or exotica like black holes.

Radio astronomers can now see the stars and use that information to search for planets around them.

Red dwarf stars were chosen as the focus of the team. They are smaller than Sun, and have magnetic activity that causes stellar flares and radio emission.

However, some stars that were magnetically inactive and older than the rest of us have also been discovered, challenging our conventional understanding.

Leiden University's Dr. Joseph Callingham, ASTRON, was the lead author of this discovery. He said that they are confident that these signals come from the magnetic connection between the stars and unseen orbiting bodies, similar to the interaction of Jupiter and Io.

He said that aurorae on Earth are commonly known as the northern and south lights. They also emit radio waves. This is due to the interaction between the planet's magnetic fields with the solar winds.

"But aurorae from Jupiter are stronger because its volcanic moon Io blasts material into space, filling Jupiter with particles that drive extraordinary aurorae.

"Our model of radio emission from stars is a scaled up version of Jupiter, Io and a planet that is enveloped by the magnetic field of a Star, feeding material into huge currents that similarly power bright Aurorae.

"It's an amazing spectacle that has captured our attention from lightyears distant."

Now, the research team wanted to confirm that the planets were indeed real.

Pope stated that while we cannot be certain that the planet hosts of the four stars that we believe have planets are actually planet hosts, we can affirm that there is a planet-star interaction as the best explanation for the phenomena we see.

"Follow up observations have ruled planets larger than Earth out, but it's not impossible to imagine a smaller planet doing this."

The first discoveries made with LOFAR are only the beginning. However, the telescope can only monitor stars that are relatively close to the telescope, up to 165 lightyears distant.

The team is excited to announce that Australia's Square Kilometer Array radio telescope has been completed. It will switch on in 2029.

Nature Astronomy published the research.

Learn more LOFAR pioneers a new way to study exoplanet environment

More information: Joseph Callingham. The population of M-dwarfs observed at low radio frequency, Nature Astronomy (2021). Journal information: Nature Astronomy Joseph Callingham, The population of M dwarfs observed at low radio frequencies,(2021). DOI: 10.1038/s41550-021-01483-0