The James Webb Space Telescope provided the most detailed weather report for two brown dwarfs, a landmark discovery that shows the kind of turmoil, sandy winds, and very high temperatures. This study sheds new light on these mysterious celestial objects often referred to as “failed stars.”
The brown dwarfs are only about 6.5 light-years from Earth and make up a binary system called WISE 1049AB. They were discovered in 2013 using NASA’s Wide-field Infrared Survey Explorer space telescope and are the closest brown dwarfs known to our solar system, thereby making them prime targets for JWST’s advanced infrared instruments.
Brown dwarfs are rather special in the cosmos and kind of act like a bridge between gas giant planets, like Jupiter, and the smallest stars known as M-dwarfs. They are small enough so that hydrogen fusion cannot be sustained in their cores, as is characteristic of true stars, yet too large in mass to be considered a planet. This makes them an exciting subject for astronomers looking for answers on stellar and planetary formation complexity.
Older brown dwarf studies have been only single snapshots in time, unable to catch their gaseous atmospheres in these very dynamic states of change. However, the new next-generation power of JWST allowed scientists to watch these changes over time. “Using JWST’s Mid-Infrared Instrument and Near-Infrared Spectrometer, a team led by Beth Biller from the University of Edinburgh conducted extensive 15-hour observations of WISE 1049AB.”.
The researchers found out that both brown dwarfs are covered in stormy weather, with temperatures ranging as high as 875 degrees Celsius, or 1,610 degrees Fahrenheit, to as low as 1,026 degrees Celsius, or 1,880 degrees Fahrenheit. Equated to sand, it would be very hot, blowing through their atmospheres. The team also detected carbon monoxide, methane, and water vapor.
The light curves graphed the brightness of the planet as a function of time and displayed variability. Therefore, they will imply stormy conditions, with gaps in the clouds that allow deeper atmospheric layers to be seen at different altitudes. Light curves also peaking at certain wavelengths would further indicate carbon monoxide, methane, and silicate grains.
The peaks led Biller’s team to infer three distinct layers of the atmosphere, with differing pressure levels. This is the most complete scanning of the vertical profile of a brown dwarf atmosphere to date. “Our results show that we are at the threshold of being able to change our understanding of worlds beyond our own,” said Biller. “These results will help us understand the conditions on giant exoplanets and eventually, potentially habitable planets, orbiting other stars,” she said.
In the paper published in Monthly Notices of the Royal Astronomical Society, this research demonstrated that JWST would finally let humanity have insight into brown dwarfs and young giant exoplanet atmospheres. According to the researchers, “This is only the beginning of what JWST will bring to light for these distant worlds with future observations.”.
Namely, JWST observations have allowed a weather report to be given in detail for these brown dwarfs, opening up avenues to study the atmosphere of exoplanets. This work has taken us one step ahead in understanding the most mysterious inhabitants of our universe.