Scientists have for the first time received a radio signal that came to us from another world. Its source is the exoplanet β Pictoris b, located 64 light-years away from us. The radiation detected by our antennas is the result of the interaction between the planet’s magnetic field and the stellar wind from its star.
The Natural Origin of the Radio Signals
Exoplanets are exotic worlds that orbit distant stars far beyond our Solar System. Since the discovery of the first exoplanets in the 1990s, astronomers have turned their attention to these distant worlds in order to learn more about them. Now, as phys.org reports, scientists have for the first time detected radio signals coming directly from one of these planets — a massive gas giant called β Pictoris b.
Previous radio signals from exoplanetary systems could not be directly linked to the planet itself because astronomers could not determine whether the signal was coming from the star or from the planet. And no, this is not evidence that alien civilizations are communicating with one another. The radio waves come from auroras associated with the planet’s powerful magnetic field.
Auroras can occur when high-energy charged particles move along a planet’s magnetic field lines and interact with the upper layers of its atmosphere. On Earth, for example, this produces the northern lights.
A team of scientists led by Kevin Ortiz Ceballos of the Harvard-Smithsonian Center for Astrophysics used the South African MeerKAT radio telescope to study the β Pictoris planetary system, located approximately 64 light-years from Earth.
Precisely Identifying the Radio Source
The scientists detected faint, repeating bursts of radio signals coming from the β Pictoris system. At first, they did not know whether the radio waves were coming from the star or from one of its planets. To determine the source precisely, the researchers compared their radio images with the exact coordinates of extremely distant background quasars, which served as fixed reference points.
This allowed them to determine the precise coordinates of both the star and the planet. When they overlaid their radio images on this map, the radio signal matched the position of β Pictoris b rather than that of its host star.
“In this paper, we report the first direct detection of auroral radio emission from an exoplanet — the giant planet β Pictoris b — using the MeerKAT radio telescope,” the team wrote in their paper published on the arXiv preprint server.
Studying the Strength of the Exoplanet’s Magnetic Field
The radio signals also made it possible to learn something about the planet itself. The researchers calculated that, at the location where the radio waves are generated, the magnetic field of β Pictoris b has a strength of at least 1,250 gauss. This is much stronger than Jupiter’s magnetic field. It is the first direct measurement of the magnetic field strength of an exoplanet.
In their paper, the authors note that their results are consistent with theoretical predictions for the strength of magnetic fields generated by young, massive giant planets.
The discovery also gives scientists a new way to directly measure the magnetic fields of exoplanets and test theoretical models of planetary structure.
