Detection of Inhomogeneous Terminators on the Exoplanet WASP-39 b Using JWST Observations

Core Concepts

The transmission spectra of the exoplanet WASP-39 b show significant differences between its morning and evening terminators, indicating inhomogeneous atmospheric properties.

Abstract

The content discusses the detection of inhomogeneous terminators on the exoplanet WASP-39 b using observations from the James Webb Space Telescope (JWST). Transmission spectroscopy has been a widely used technique to study the physical and chemical properties of exoplanet atmospheres. However, the classical assumption of a homogeneous terminator region has been challenged in the past decade for highly irradiated, hot gas giant exoplanets.
The key highlights from the content are:

The authors report the detection of inhomogeneous terminators on the exoplanet WASP-39 b using JWST observations in the near-infrared (2-5 μm) wavelength range.
They observe larger transit depths in the evening terminator, which are on average 405±88 ppm larger than the morning terminator, and also have qualitatively larger features.
The spectra are best explained by models in which the evening terminator is hotter than the morning terminator by 177^{+65}_{-57} K, with both terminators having C/O ratios consistent with solar.
General circulation models (GCMs) predict temperature differences broadly consistent with the observed values and suggest a cloudy morning terminator and a clearer evening terminator.
This study provides the first direct detection of morning and evening transmission spectra in a wide wavelength range for an exoplanet, challenging the classical assumption of a homogeneous terminator region.

Stats

The evening terminator of WASP-39 b has transit depths that are on average 405±88 ppm larger than the morning terminator.
The evening terminator is hotter than the morning terminator by 177^{+65}_{-57} K.

Quotes

"While models predict clear differences between the evening (day-to-night) and morning (night-to-day) terminators, direct morning/evening transmission spectra in a wide wavelength range has not been reported for an exoplanet to date."
"We observe larger transit depths in the evening which are, on average, 405±88 ppm larger than the morning ones, also having qualitatively larger features than the morning spectrum."
"The spectra are best explained by models in which the evening terminator is hotter than the morning terminator by {177}_{-57}^{+65} K with both terminators having C/O ratios consistent with solar."

Key Insights Distilled From

Inhomogeneous terminators on the exoplanet WASP-39 b - Nature

by Nést... at www.nature.com 07-15-2024

https://www.nature.com/articles/s41586-024-07768-4

Deeper Inquiries

How do the observed differences in the morning and evening terminators of WASP-39 b relate to the planet's overall atmospheric circulation and energy transport

The observed differences in the morning and evening terminators of WASP-39 b provide valuable insights into the planet's atmospheric circulation and energy transport mechanisms. The larger transit depths in the evening terminator, along with the qualitative differences in the spectra, suggest variations in temperature and composition between the two terminators. These differences indicate a complex atmospheric circulation pattern on the exoplanet, where energy is redistributed unevenly between the day and night sides. The hotter evening terminator and the presence of larger features in its spectrum imply a more active energy transport process, possibly driven by strong winds or atmospheric dynamics. On the other hand, the cooler morning terminator with cloudy features suggests a different energy balance and circulation pattern. Overall, these observations highlight the dynamic nature of WASP-39 b's atmosphere and the importance of considering inhomogeneous terminators in studying exoplanet atmospheres.

What other exoplanets might exhibit similar inhomogeneous terminator properties, and how could future observations help characterize the diversity of exoplanet atmospheric structures

Similar inhomogeneous terminator properties may be present in other highly irradiated, hot gas giant exoplanets like WASP-39 b. Planets with comparable equilibrium temperatures (Teq ≳ 1000 K) and intense stellar irradiation are more likely to exhibit diverse terminator structures due to the extreme conditions they experience. Future observations using advanced telescopes like the James Webb Space Telescope (JWST) can help characterize the diversity of exoplanet atmospheric structures by conducting detailed transmission spectroscopy of a wider range of exoplanets. By studying morning and evening terminator spectra across different exoplanetary systems, researchers can identify common patterns or variations in atmospheric circulation, energy transport, and composition. This comparative analysis will enhance our understanding of the atmospheric dynamics of hot gas giant exoplanets and provide valuable insights into the factors shaping their atmospheric properties.

What implications do the findings of this study have for our understanding of the formation and evolution of hot gas giant exoplanets like WASP-39 b

The findings of this study on WASP-39 b have significant implications for our understanding of the formation and evolution of hot gas giant exoplanets. The detection of inhomogeneous terminators and the distinct morning/evening transmission spectra suggest complex atmospheric processes at play in these extreme environments. The temperature differences between the terminators, along with the consistent C/O ratios with solar values, indicate that the atmospheric composition of WASP-39 b is influenced by both internal and external factors. The presence of cloudy features in the morning terminator and clearer conditions in the evening terminator point towards a dynamic atmospheric structure shaped by cloud formation and circulation patterns. These insights can help refine theoretical models of exoplanet formation and evolution, shedding light on the mechanisms driving the atmospheric dynamics of hot gas giant exoplanets.