Using NASA's James Webb Space Telescope, researchers observed a broad infrared spectrum from SIMP 0136 over two full rotations. This analysis revealed dynamic cloud layers, fluctuating temperatures, and changing carbon chemistry, previously undetectable.
These findings offer valuable insights into the intricate atmospheres of gas giants within and beyond our solar system. Such studies are crucial for the upcoming direct imaging of exoplanets by NASA's Nancy Grace Roman Space Telescope, set to launch in 2027.
Before the Webb observations, scientists had extensively examined SIMP 0136 using ground-based telescopes and NASA's Hubble and Spitzer space telescopes.
"We knew its brightness varied, suggesting patchy cloud layers rotating and evolving over time," said Allison McCarthy, a doctoral student at Boston University and lead author of the study published in The Astrophysical Journal Letters. "We suspected temperature fluctuations, chemical processes, and possibly auroral effects were also influencing its brightness, but we lacked confirmation."
Webb's precise capability to monitor brightness variations across a wide spectral range provided the necessary data to investigate these hypotheses.
This produced an extensive set of light curves, each mapping brightness fluctuations at specific wavelengths as the object rotated.
"The ability to watch an object's full spectrum shift in real time was incredible," said principal investigator Johanna Vos of Trinity College Dublin. "Previously, we had only a narrow slice of the near-infrared spectrum from Hubble and a few brightness readings from Spitzer."
The team immediately noticed that different wavelengths exhibited distinct light-curve patterns, suggesting multiple factors influence SIMP 0136's brightness.
"If we were observing Earth from afar, different wavelengths would reveal different surface and atmospheric features," explained co-author Philip Muirhead of Boston University. "Oceans, vegetation, and landmasses would all contribute to varying color patterns."
"Each wavelength provides information about a specific atmospheric depth," McCarthy explained. "We found that wavelengths with similar light-curve patterns originated at the same altitudes, confirming they shared a common underlying cause."
The observations identified three primary atmospheric components. Deep in the atmosphere, patchy clouds composed of iron particles influence brightness changes. Higher up, clouds of silicate mineral grains also contribute to variability. A third set of light curves, originating at very high altitudes, tracks temperature fluctuations and may be linked to auroral activity detected at radio wavelengths or hot gas upwelling from deeper layers.
Other spectral variations hint at changes in atmospheric carbon chemistry. Rotating pockets of carbon monoxide and carbon dioxide, or chemical reactions altering atmospheric composition over time, could explain these fluctuations.
"We're still working to understand the chemistry," Vos noted. "But our findings suggest that molecules like methane and carbon dioxide may vary across different regions and timescales. When studying exoplanets, we must consider that a single measurement might not represent the entire planet."
Research Report:The JWST Weather Report from the Isolated Exoplanet Analog SIMP 0136+0933: Pressure-dependent Variability Driven by Multiple Mechanisms
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