Using the Dutch-led Low Frequency Array (LOFAR) radio telescope, astronomers have discovered unusual radio waves coming from the nearby red dwarf star GJ1151. The radio waves bear the tell-tale signature of aurorae caused by an interaction between a star and its planet. The radio emission from a star-planet interaction has been predicted for over thirty-years but this is the first time astronomers have been able to discern its signature. This method, only possible with a sensitive radio telescope like LOFAR, opens the door to a new way of discovering exoplanets in the habitable zone and studying the environment they exist in.
Red dwarfs are the most abundant type of star in our Milky Way, but much smaller and cooler than our own Sun. This means for a planet to be habitable, it has to be significantly closer to its star than the Earth is to the Sun. Red dwarfs also have much stronger magnetic fields than the Sun, which means, a habitable planet around a red dwarf is exposed to intense magnetic activity. This can heat the planet and even erode its atmosphere. The radio emissions associated with this process are one of the few tools available to gauge the potency of this effect. ...
Coherent Radio Emission from a Quiescent Red Dwarf Indicative of Star-Planet Interaction ~ H. K. Vedantham et al
<<A whistler is a very low frequency or VLF electromagnetic (radio) wave generated by lightning. Frequencies of terrestrial whistlers are 1 kHz to 30 kHz, with a maximum amplitude usually at 3 kHz to 5 kHz. Although they are electromagnetic waves, they occur at audio frequencies, and can be converted to audio using a suitable receiver. They are produced by lightning strikes (mostly intracloud and return-path) where the impulse travels along the Earth's magnetic field lines from one hemisphere to the other. They undergo dispersion of several kHz due to the slower velocity of the lower frequencies through the plasma environments of the ionosphere and magnetosphere. Thus they are perceived as a descending tone which can last for a few seconds. Voyager 1 and 2 spacecraft detected whistler-like activity in the vicinity of Jupiter known as "Jovian Whistlers", implying the presence of lightning there.>>