Astronomers reverse the conventional process to find a brown dwarf, or super planet, with the LOFAR telescope in Hawaii.
Scientists detected spectral signals from the brown dwarf BDR J1750 + 3809 (or Elegast) while studying data collected by the LOFAR telescope at the Mauna Kea Observatory in Hawaii, operated by the University of Hawaii. The new study is published in The Astrophysical Journal Letters on November 9.
This is the first time that researchers have used a radio telescope to identify and describe a cold brown dwarf star, also known as a superstar. Until now, astronomers have mainly relied on infrared light investigations to find this type of celestial object.
“This discovery opens up a new way to find cold objects floating near the Sun. They are too faint to be observed using the methods we’ve been using for 25 years,” study co-author Michael Liu, astronomer at the University of Hawaii, said.
Brown dwarfs fall between the boundaries of the largest planets and the smallest stars. Although they don’t have enough mass to support the fusion reaction, they still emit radio waves. Like Jupiter and other gas giants, thick-atmosphere brown dwarfs have strong magnetic fields and are able to accelerate charged particles. These particles emit radio waves and provide energy for electromagnetic phenomena such as the Northern Lights.
Previously, scientists had also observed radio signals from distant brown dwarfs, but only after being detected by infrared surveys. In the new study, astronomers are reversing this process. They located the brown dwarf using data from LOFAR and used Mauna Kea’s infrared telescopes for further observations.
To differentiate the signals emitted by brown dwarfs from distant galaxies, the team focused on circular polarized radio waves, a characteristic unique to stars, planets, and brown dwarfs. After identifying a weak polarizing radio wave signal in the LOFAR data, they examined archived images from other observatories, including the Gemini-North Telescope and NASA’s Infrared Telescope. (IRTF), to confirm the new discovery.
Data from SPeX, IRTF’s ultra-sensitive spectrometer, allows scientists to detect methane in a distant celestial atmosphere, a hallmark of brown dwarfs. “This shows that the efficiency of SpeX has increased after being upgraded to modern electronics and infrared devices in 2015,” said John Rayner, astronomer at the University of Hawaii.