4 min readKochiOct 14, 2021 03:47 PM IST
First published on: Oct 14, 2021 at 03:46 PM IST
On October 13, several news websites reported that Earth has received its first radio signals from outside our solar system and speculated that it could be ‘aliens calling.’
The articles were based on a paper published on October 11 in Nature Astronomy. The researchers said that they had discovered radio signals from 19 distant red dwarf stars or M dwarfs. M dwarfs are stars smaller than our Sun and are known to have magnetic field strength about thousand times of the magnetic field of our Sun.
The study team used the world’s most powerful radio telescope called LOFAR or Low Frequency Array situated in the Netherlands for their exoplanet search.
Interaction between star and its planets
In a release, the team notes that the radio signals could be coming from interactions between the M dwarf and planets around them. Dr. Joseph Callingham, lead author of the discovery, said the team is confident these signals are coming from the magnetic connection of the stars and unseen orbiting planets, similar to the interaction between Jupiter and its moon, Io.
“Our own Earth has aurorae, commonly recognised 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,” he said. “But in the case of aurorae from Jupiter, they’re much stronger as 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.”
So is there a planet around this M-dwarf?
Sujan Sengupta, from the Indian Institute of Astrophysics, Bengaluru, who was not involved in the study explains: “Firstly, there is no way to determine if there is really an interaction. Secondly, if it’s due to the interaction of the magnetic fields of two objects, there is no way to prove that it’s a planet. We know very well that these kinds of stars (M-dwarfs) have a very strong magnetic field and emit radio waves through standard mechanisms. But how the detected low frequency radio signal has originated needs further research.”
Dr. Sengupta is Professor and Chair of the Theoretical Astrophysics Group at IIA and his area of research includes brown dwarfs (astronomical objects which have the size between that of a giant planet and that of a small star), extrasolar planets and neutron stars.
He adds that since these are the only planet hosting stars showing low frequency radio emission, the observation needs to be confirmed by other radio telescopes and by other groups independently.
“If they claim to have discovered a planet for the first time through radio emission, they must find out the mass of the secondary object. Otherwise it may be a brown dwarf or even an unresolved low mass companion (another M dwarf with strong magnetic field). If they cannot characterise the secondary object, they cannot claim it to be a planet just from an unusual radio signal from the star. It might be a possibility only. I think it’s too early to say that the detected low frequency radio wave implies the presence of a planet around the star,” he notes.
Artist impression of a red-dwarf star’s magnetic interaction with its exoplanet. (Danielle Futselaar/artsource.nl via astron.nl)
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