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| Study reveals patchy clouds and shifting atmospheric layers on a free-floating planetary-mass object just 20 light-years away, offering potential insights into planet and star formation Image Credit: Anastasiia Nahurna. |
Researchers at McGill University and collaborating institutions have mapped the atmospheric features of a planetary-mass brown dwarf, a type of space object that is neither a star nor a planet, existing in a category in-between. This particular brown dwarf’s mass, however, is just at the threshold between being a Jupiter-like planet and a brown dwarf. It has thus also been called a free-floating, or rogue, planet, not bound to a star. Using the James Webb Space Telescope (JWST), the team captured subtle changes in light from SIMP 0136, revealing complex, evolving weather patterns across its surface.
“Despite the fact that right now we cannot directly image habitable planets around other stars, we can develop methods of learning about the meteorology and atmospheric composition on very similar worlds,” said Roman Akhmetshyn, a McGill MSc student in physics and the study's lead author.
SIMP 0136 sits about 20 light-years away in the direction of the constellation Pisces. With a mass about 13 times that of Jupiter, it’s too small to sustain the nuclear fusion that powers stars, but too large to be considered an ordinary planet. It probably formed like a star before cooling and dimming over hundreds of millions of years.
SIMP 0136 is a free-floating planet, drifting alone through space, and its isolated environment makes it an ideal laboratory for studying the atmospheres of gas giants without interference from starlight.
Peering into alien clouds
The researchers used JWST’s Near-Infrared Imager and Slitless Spectrograph (NIRISS), a Canadian-built instrument developed by the Canadian Space Agency, the Université de Montréal (UdeM) and other partners, to observe the object for a full rotation, lasting only 2.4 hours. These data were collected as part of a Guaranteed Time Observations program led by UdeM astronomer Étienne Artigau. This time on the telescope was reserved for Canadian astronomers in exchange for the contribution of the NIRISS instrument to the JWST mission.
By analyzing minute fluctuations in brightness at different wavelengths, the team discovered that SIMP 0136’s light is shaped by at least three distinct atmospheric layers. Each layer contains clouds made of different materials, such as forsterite (a rock) and iron, with varying temperatures and chemical compositions.
“We suspect numerous small-scale patchy clouds of different temperatures and chemistry, scattered across the globe,” said Akhmetshyn. "Although we couldn't create a meteorological map of SIMP 0136, we determined that some atmospheric layers have clear signs of north-south asymmetry." This asymmetry is important since it means that future efforts to map the atmospheres of these planets will have to do so in two dimensions: longitude and latitude.
A new way to study exoplanet atmospheres
The study also showed that no single model could explain the observed data; only a combination of several atmospheric models could reproduce the spectrum. That finding supports theories that brown dwarfs and giant exoplanets have chaotic, fast-changing weather, similar to Jupiter’s bands but far more turbulent.
Understanding such variability could help scientists interpret signals from distant exoplanets.
The work demonstrates the power of JWST to probe alien worlds beyond our solar system in unprecedented detail. As Webb continues to observe similar targets, researchers hope to refine their techniques to map not just temperature and clouds, but also wind patterns and chemical cycles on alien worlds.
Published in journal: The Astrophysical Journal
Title: Mapping Atmospheric Features of the Planetary-mass Brown Dwarf SIMP 0136 with JWST NIRISS
Authors: Roman Akhmetshyn, Étienne Artigau, Nicolas B. Cowan, Michael K. Plummer, Fei Wang, Ben Burningham, Björn Benneke, René Doyon, Ray Jayawardhana, David Lafrenière, Stanimir A. Metchev, and Jason F. Rowe
Source/Credit: McGill University
Reference Number: ps110725_01
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