First direct radio discovery of a brown dwarf

© CC-BY-SA; Image credit: ASTRON/Danielle Futselaar

Brown dwarfs (BD) span the range from the lowest mass stars (that burn hydrogen) to the most massive exoplanets. They have magnetospheres similar to the one around Jupiter, and some even display aurorae and cyclotron radio emission. So far BDs have been discovered by their faint infrared glow. Using data from the ongoing LoTSS survey on LOFAR, we have achieved the first direct radio discovery of a BD. The BD, nicknamed Elegast, is cold enough to have methane in its atmosphere, making it a close cousin of Jupiter-like exoplanets. The discovery shows that radio observations can be used to find objects that are too cold and hence too faint to be found in large infrared surveys. It also puts us on an exciting path to test theories that predict the magnetic field strength of exoplanets.

The image shows an artist's impression of Elegast. The blue loops depict the magnetic field lines along which spiralling electrons emit radio waves that LOFAR detects. Some electrons eventually impact the polar regions generating aurorae.

The paper detailing the discovery has been published in ApJ Letters here and on the arXiv preprint server here

A press release announcing the discovery can be found here.