📻 First direct detection of radio waves from an exoplanet

For the first time, astronomers have located radio waves directly on a planet outside the Solar System.

This planet, β Pictoris b, is a gas giant orbiting the star β Pictoris. Until now, radio signals had already been detected in systems hosting exoplanets. But it remained difficult to determine whether these emissions actually came from the planet or its star.

The researchers used MeerKAT, a radio telescope array installed in South Africa. They observed β Pictoris b several times and detected very brief radio bursts. Their position corresponds to that of the planet rather than the star. The signals were recorded between 0.85 and 3.5 GHz.

Another clue is that these waves possess a property typical of emissions produced by charged particles guided by a magnetic field. In the Solar System, a comparable phenomenon accompanies the auroras of several planets. The authors therefore believe they are observing auroral emission from β Pictoris b.

This detection primarily makes it possible to directly estimate the planet's magnetic field. Its strength could reach at least 1,250 gauss in the region where the radio waves originate. By comparison, the magnetic field measured at Earth's surface is less than 1 gauss.

A magnetic field provides information about what is happening inside a planet. It can also alter the way its atmosphere interacts with particles emitted by its star. Until now, these fields had remained very difficult to measure directly on exoplanets.

The result nevertheless still requires confirmation. The study has been submitted to arXiv and has not yet undergone the complete peer-review process of a scientific journal. The authors did, however, find emissions in several observations, with consistent characteristics.

Future radio observations may search for the same type of signal around other worlds. This method would then provide access to a property of exoplanets that has so far been largely inaccessible: their magnetic field.