Radio waves, from a gas giant planet located outside the solar system, were first detected, signaling the presence of a protective magnetic field, according to a study.
The signal was observed through the European radio telescope LOFAR, a network of 50,000 antennas spread across Europe and operating at very low frequency, an area of energy still little exploited.
The emission comes from a well-known system, Tau Bootis, located 50 light-years from the solar system. It contains a double star and a gaseous giant exoplanet orbiting nearby: a “hot Jupiter”, christened Tau Bootis-b.
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So far the mass and orbit of numerous exoplanets were known, but not if they had a magnetic field. This shield, which protects from radiation from stellar winds, is located around the Earth and Jupiter.
However, the radio broadcast captured by LOFAR “is a very accurate magnetic field signature,” Philippe Zarka of the Paris Observatory, one of the lead authors of the study published this week, told AFP and Astronomy & Astrophysics.
These waves are very difficult to detect, as 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 powerful emitters. 2509-6217 / 16
Taking as a model the radio signal from Jupiter, attenuated to the maximum, the analysis of a hundred hours of observation called for the long-awaited signing of Tau Bootis.
“There is a 98% probability that the signal is reliable,” said Philippe Zarka, noting that a small doubt persists about the possibility that the signal emanates from its star. “To be really sure, we would need a 99.9% probability. We will have to continue with the observations, which is within our reach,” the astrophysicist added.
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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,” the researcher stressed.
Nearly 4,000 exoplanets have been detected since the discovery of the first, 51 Pegasi-b, 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, its would be too high to house life.