Jan 09, 2024 - Astronomers using James Webb Space Telescope have made a groundbreaking discovery, uncovering unexpected infrared emissions from methane on a cold, isolated brown dwarf known as W1935. This mysterious finding, presented at the 243rd meeting of the American Astronomical Society in New Orleans, suggests possible auroral processes at play, challenging our understanding of such phenomena beyond our solar system.

A Detective Story:

Led by astronomer Jackie Faherty from the American Museum of Natural History in New York, the discovery unfolded like a detective story. The team, awarded time with the Webb telescope, investigated 12 cold brown dwarfs, including W1935. Discovered by citizen scientist Dan Caselden through the Backyard Worlds zooniverse project, W1935 and another brown dwarf, W2220, appeared as near clones in composition, brightness, and temperature. However, W1935 exhibited unexpected methane emission instead of absorption.

The Mystery of Methane Emission:

The team turned to computer models to understand the unusual methane emission. While W2220 had an expected distribution of energy throughout its atmosphere, W1935 showed a surprising temperature inversion, getting warmer with increasing altitude. This phenomenon is typically observed in planets with nearby stars that heat the stratosphere, making W1935's temperature inversion a puzzling revelation.

Clues from Our Solar System:

To unravel the mystery, astronomers looked closer to home for clues. Gas giant planets in our solar system, particularly Jupiter and Saturn, exhibit temperature inversions. The team speculated that external heating by aurorae and internal energy transport could be responsible for stratospheric heating in these planets. However, W1935 lacks a companion star, ruling out the possibility of a stellar wind contributing to the observed phenomenon.

Brown Dwarf Aurora Candidates in Context:

This isn't the first time astronomers have used aurorae to explain brown dwarf observations. While radio emission from warmer brown dwarfs has been detected, W1935 marks the first auroral candidate outside the solar system with methane emission signatures. It also stands as the coldest auroral candidate, with an effective temperature of about 400 degrees Fahrenheit, making it approximately 600 degrees Fahrenheit warmer than Jupiter.

Significance of the Discovery:

With W1935, scientists now have a unique opportunity to explore a solar system phenomenon extended beyond the reach of stellar irradiation. Jackie Faherty noted, "With Webb, we can really 'open the hood' on the chemistry and unpack how similar or different the auroral process may be beyond our solar system." This discovery highlights the James Webb Space Telescope's role as the world’s premier space science observatory, continually unraveling mysteries within our solar system and beyond.

NASA's Webb Telescope continues to redefine our understanding of the cosmos. The discovery of possible aurorae on the isolated brown dwarf W1935 challenges conventional wisdom, emphasizing the importance of continued exploration and the invaluable insights provided by cutting-edge space telescopes like Webb. As scientists delve deeper into the universe's mysteries, each revelation brings us closer to understanding our place in the vast expanse of space.

Source - NASA