Scientists have spotted radio waves from an exoplanet for the first time, and the signal appears to come from Beta Pictoris b itself rather than the star it orbits. The finding, based on observations with MeerKAT in South Africa, points to a planet that may be generating auroras and carrying a magnetic field far stronger than Earth’s.
That is why the result is drawing attention now. Beta Pictoris b is a gas giant about 63 light-years away, and the team traced circularly polarized radio waves to the planet after separating them from the much brighter activity of the star. Yvette Cendes said people hear “radio signal from an exoplanet” and think aliens, but “it’s not aliens,” adding that the team could rule out the star and say the emission came from “this one particular planet.”
The signal matters because auroras can produce circularly polarized radio waves when charged particles move through a planet’s magnetic field. On Earth, that process creates the northern lights, and it also happens on Jupiter, Saturn and Mars. Scientists have seen auroras on brown dwarfs before, but those objects are not planets. In this case, the data suggest Beta Pictoris b may have a magnetic field of more than 1,000 gauss, compared with about half a gauss for Earth.
That estimate fits a world that is also massive, at about 10 times Jupiter’s mass, and may spin once every eight hours or so. A fast rotation would help drive the kind of magnetic activity that can produce auroras, but the interpretation is not yet locked in. Joe Callingham said the result “if it holds up in peer review” would be “an incredibly exciting advancement,” and added that seeing pulsation in the radio waves would make the aurora case far stronger.
The paper was submitted to arXiv.org on September 15, so the next test is not more excitement but more proof. If follow-up observations show the radio signal changing in step with the planet’s spin, the first radio detection from an exoplanet could also become the clearest direct evidence yet of a planetary magnetic field beyond the solar system.
