The radio waves, coming from a giant gas planet located outside the solar system, were detected for the first time, signaling the presence of a magnetic field of protection, according to a study.
The signal was observed through the European radio telescope LOFAR, a network of 50,000 antennas spread throughout Europe and operating at a very low frequency, an area of energy that is still little exploited.
The emission comes from an already known system, Tau Bootis, located 50 light years from the solar system. It contains a double star and a giant gaseous exoplanet that orbits closely: a “hot Jupiter”, nicknamed Tau Bootis-b.
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Until now, the mass and orbit of many exoplanets were known, but not if they had a magnetic field. This shield, which protects against radiation from stellar winds, is found around the Earth and Jupiter.
However, the radio broadcast captured by LOFAR “is a very precise signature of the magnetic field,” Philippe Zarka of the Paris Observatory, one of the lead authors of the study published this week in Astronomy & Astrophysics, told AFP.
These waves are very difficult to detect because the planetary magnetic fields are usually weak and their source of emission far away.
The international team of researchers observed three extrasolar systems (Tau Bootis, 55 Cancri and Ups) that contain gas giants that, being close to their star, are probably strong emitters. 2509-6217 / 16
Taking as a model the radio signal of Jupiter, attenuated to the maximum, the analysis of one hundred hours of observation supported the expected signature of Tau Bootis.
“There is a 98% probability that the signal is reliable,” said Philippe Zarka, noting that there is little doubt about the possibility of the signal emanating from its star. “To be really sure, you would need a 99.9% probability. We will have to continue with the observations, which are within our reach “, added the astrophysicist.
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If confirmed, “it would be a first that would validate the radio detection technique and, therefore, a step towards the characterization of exoplanets,” said the researcher.
About 4,000 exoplanets have been detected since the first, 51 Pegasi-b, was found 25 years ago.
The existence of a magnetic “bubble” around it is an ingredient conducive to the development of a way of life, according to Philippe Zarka. But there are other criteria, such as temperature, and in the case of Tau Bootis-b, hers would be too high to support life.