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Astronomers first discovered a cold brown dwarf – otherwise known as a “super planet” – using a radio telescope.
Brown dwarfs are large, ranging in size from 15 to 75 times the mass of Jupiter, and have gaseous atmospheres similar to some of the planets in our solar system. They are also often known as “failed stars” due to the way they shine.
Planets shine by reflecting light, while stars shine by producing their own light. Despite being so large, brown dwarfs are unable to sustain the nuclear fusion of hydrogen into helium – which makes stars shine – hence their name.
This brown dwarf, classified BDR J1750 + 3809 and named “Elegast”, is the first substellar object to be detected by radio observations. Usually, these stellar objects are detected via infrared celestial surveys.
Although brown dwarfs do not undertake fusion reactions, they emit light at radio wavelengths in a way similar to Jupiter: accelerating charged particles such as electrons to produce radiation including radio waves and auroras.
Radio emissions were only detected by a small number of brown dwarfs and all had previously been detected by infrared surveys.
The discovery of this brown dwarf through radio telescopes shows that astronomers can detect objects that are too cold and faint to be detected by infrared investigations. This opens the door to the detection of other bodies such as free-floating gas giant exoplanets.
“We asked ourselves, ‘Why point our radio telescope at the cataloged brown dwarfs?'” Said Harish Vedantham, lead author of the study and astronomer at ASTRON (Dutch Institute of Radio Astronomy).
“Let’s just take a big picture of the sky and discover these objects directly on the radio.”
Elegast was discovered using data from the Low-Frequency Array (LOFAR) telescope in Europe, and then confirmed using telescopes on the summit of Maunakea in Hawaii.
The new research was published in Letters from astrophysics journals November 9, written by Vedantham and co-authored by astronomer Michael Liu and graduate student Zhoujian Zhang.
“This work opens up an entirely new method for finding colder objects floating in the vicinity of the Sun that would otherwise be too faint to be detected by the methods used over the past 25 years,” Liu said.
This discovery could also help astronomers measure the magnetic fields of exoplanets, as cold brown dwarfs are the most exoplanet-like bodies that scientists can measure with radio telescopes.
As such, it could shed new light on the prediction of another planet’s magnetic field, which is vital for determining its atmospheric properties and the evolution of other worlds.
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