Strange radio signals lead to detection of Earth-like exoplanet with magnetic fields

These two were chosen because the planet orbits close to the star and completes an orbit in just two days. Astronomers were able to detect repeating radio signals originating from the star YZ Ceti after conducting extensive observations. 

The study was led by researchers Sebastian Pineda and Jackie Villadsen, who used observations from the Karl G. Jansky Very Large Array, a radio telescope operated by the National Radio Astronomy Observatory of the National Science Foundation in the United States.

The team hypothesizes that radio signals could be the result of particle interactions between this exoplanet's magnetic field and its star. As the planet orbits close to its star, it emits powerful radio waves, which they were able to study from Earth. 

This proximity, however, causes an unusual phenomenon. YZ Ceti b orbits its star so close that the exoplanet "plows" the charged material back towards the star. The magnetic field of the planet directs charged plasma back toward its star. As a result, the energetic particles come into contact with the star's magnetic field, causing an aurora to form on the star.

Radio signals from star's aurora

This implies that the radio signals recorded came from the star's aurora. Researchers can estimate the strength of this planet's magnetic field by measuring the power of radio waves.

"We're actually seeing the aurora on the star — that's what this radio emission is. There should also be aurora on the planet if it has its own atmosphere," Pineda said in a statement.

According to the authors, the study provides one of the best examples of a potential magnetic field on an exoplanet. The team is planning to conduct further follow-up work to confirm the actual source of radio waves.

"There are a lot of new radio facilities coming online and planned for the future. Once we show that this is really happening, we'll be able to do it more systematically. We're at the beginning of it," added Pineda.

This new research offers a promising method for detecting magnetic fields on planets outside our solar system. The research was funded by the National Science Foundation (NSF) and was published in the journal Nature Astronomy.

Study Abstract:

Observing magnetic star–planet interactions (SPIs) offers promise for determining the magnetic fields of exoplanets. Models of sub-Alfvénic SPIs predict that terrestrial planets in close-in orbits around M dwarfs can induce detectable stellar radio emission, manifesting as bursts of strongly polarized coherent radiation observable at specific planet orbital positions. Here we present 2–4 GHz detections of coherent radio bursts on the slowly rotating M dwarf YZ Ceti, which hosts a compact system of terrestrial planets, the innermost of which orbits with a two-day period. Two coherent bursts occur at similar orbital phases of YZ Ceti b, suggestive of an enhanced probability of bursts near that orbital phase. We model the system’s magnetospheric environment in the context of sub-Alfvénic SPIs and determine that YZ Ceti b can plausibly power the observed flux densities of the radio detections. However, we cannot rule out stellar magnetic activity without a well-characterized rate of non-planet-induced coherent radio bursts on slow rotators. YZ Ceti is therefore a candidate radio SPI system, with unique promise as a target for long-term monitoring.