Faint Super Planet Discovered by Radio Telescope

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Artist’s impression of the discovery dubbed, Elegast. Credit: ASTRON / Danielle Futselaar

Astronomers used observations from a radio telescope and a pair of observatories on Maunakea to discover a cold brown dwarf, also known as a “super planet” or “failed star.”

The discovery, designated BDR J1750+3809, is the first substellar object detected through radio observations—until now, brown dwarfs have largely been found from infrared sky surveys. The brown dwarf was identified with a Low-Frequency Array (LOFAR) radio telescope in Europe and then confirmed using telescopes on the summit of Maunakea, namely the International Gemini Observatory and the NASA InfraRed Telescope Facility (which is operated by the University of Hawai‘i).

Officials with the University of Hawai‘i at Mānoa’s Institute for Astronomy (IFA) say this discovery is a significant breakthrough because it demonstrates that astronomers can detect objects that are too cold and faint to be found in infrared surveys, and perhaps even detect free-floating gas-giant exoplanets.


“This work opens a whole new method to finding the coldest objects floating in the Sun’s vicinity, which would otherwise be too faint to discover with the methods used for the past 25 years,” said Astronomer Michael Liu.

Liu and graduate student Zhoujian Zhang at IFA co-authored a paper on the discovery, which was published in The Astrophysical Journal Letters.

Radio emissions have previously been detected from only a handful of cold brown dwarfs, which were discovered and cataloged by infrared surveys before being observed with radio telescopes. The team decided to flip this strategy, using a sensitive radio telescope to discover cold, faint radio sources and then perform follow-up infrared observations with Maunakea telescopes to categorize them.


As well as being an exciting result in its own right, the discovery of BDR J1750+3809 could provide a glimpse into a future when astronomers can measure the properties of exoplanets’ magnetic fields. Cold brown dwarfs are the closest things to exoplanets that astronomers can currently detect with radio telescopes, and this discovery could be used to test theories predicting the magnetic field strength of exoplanets. Magnetic fields are an important factor in determining the atmospheric properties and long-term evolution of exoplanets.

Click here to read the full press release from UH Mānoa.

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