A possible presence of hidden exoplanets detected in radio emissions

Artist's concept of red dwarf magnetically interacting with a planet (Image courtesy Danielle Futselaar (artsource.nl))
Artist’s concept of red dwarf magnetically interacting with a planet (Image courtesy Danielle Futselaar (artsource.nl))

Two articles – one published in the journal “Nature Astronomy” and one published in “The Astrophysical Journal Letters” – report different aspects of the discovery of radio wave emissions from 19 red dwarfs of which at least 4 could have originated from interaction with unknown planets. This study is based on detections obtained with the LOFAR radio telescope to examine the stellar magnetic activity of 19 red dwarfs. Radio emissions have also been detected from ancient and magnetically inactive stars. Data collected by NASA’s TESS space telescope was also added to get a more complete picture of that activity. The most likely explanation is that there’s an interaction with the magnetic field of planets that haven’t been detected.

In the solar system, it’s possible to study the radio wave emissions generated by the interaction between the solar wind and the planets’ magnetic field, which can also result in auroras. These phenomena are even more intense in Jupiter’s case because there’s an interaction with its moon Io, whose volcanoes emit a lot of charged particles that collide with the planetary magnetic field.

The idea of ​​detecting that kind of interaction between other stars and exoplanets in other star systems has existed for several years. This type of research is a remarkable development of radio astronomy applied to the search for exoplanets but is far from easy to carry out. The LOFAR (Low Frequency Array) radio telescope is based on a network of antennas scattered around Europe and has the sensitivity needed to go a little beyond the nearest stars, and for this reason, it has been used to examine the magnetic activity of a group of stars. Red dwarfs are the smallest stars but they can be very active and are also the most common, so this research studied a sample of 19 of these stars.

Among the stars in the study sample, 4 are ancient and have exhausted the strong magnetic activity typical of younger red dwarfs. Despite that, radio wave emissions arrived from them as well. According to the researchers, the most likely explanation is that those emissions are generated by interactions of their stellar winds with exoplanets orbiting them. The problem is that none of these possible exoplanets have been detected through the various methods used by astronomers.

The researchers used data collected by the TESS space telescope as well to obtain more information on the stars under study. TESS is a planet hunter that can detect their passage in front of their star but in this case it detected none. Its observations remain useful in providing information on those stars’ activity and in particular on the flares they emit.

The researchers remain convinced that there are planets orbiting the 4 ancient stars with anomalous radio emissions. It could be impossible or at least difficult to detect those planets for current instruments. The new phase of the research consists of follow-up observations of those 4 stars for a more in-depth study. The studies with the LOFAR radio telescope also continue to gather more information but the big leap forward will come at the end of this decade, when SKA, the next-generation radio telescope, will be activated. Among the progress it will enable, it could make it possible to make a leap forward in the research and study of exoplanets.

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