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Alien weather: The changing atmosphere of exoplanet WASP-121 b

An international team of astronomers has utilized the NASA/ESA Hubble Space Telescope to examine the atmosphere of the exoplanet WASP-121 b, revealing fascinating insights into its changing environment.

The team, working over several years, reprocessed observations from 2016, 2018, and 2019. This effort resulted in a unique dataset allowing them to not only analyze WASP-121 b’s atmosphere but also to compare its state across these years.

Temporal variations

The findings were remarkable. The experts observed clear evidence of temporal variations in WASP-121 b’s atmosphere. 

Sophisticated modeling techniques suggested these changes could be attributed to weather patterns on the exoplanet.

Observing distant exoplanets

Observing distant exoplanets is challenging. Their vast distance from Earth and the overshadowing brightness of their host stars make it difficult to gather data. 

Hubble’s advanced capabilities and the accumulation of long-term data, however, have made such detailed observations possible.

WASP-121 b, or Tylos, is a well-studied “hot Jupiter” situated about 880 light-years away and completing an orbit every 30 hours. Its close proximity to its host star results in extremely high temperatures, particularly on the star-facing hemisphere.

Detailed data assembly

The team’s approach involved combining four sets of Hubble observations using the Wide Field Camera 3. This included two sets of phase-curves and observations of the exoplanet transiting both in front of and behind its star.

Exoplanet data processing is both time-consuming and complex. Despite this, the team’s efforts paid off, allowing them to directly compare data across different observation sets.

Dynamic view of WASP-121 b

Quentin Changeat is an ESA research fellow at the Space Telescope Science Institute and one of the principal investigators of the team.

“Our dataset represents a significant amount of observing time for a single planet and is currently the only consistent set of such repeated observations,” said Changeat.

“The information that we extracted from those observations was used to characterize (infer the chemistry, temperature, and clouds) of the atmosphere of WASP-121 b at different times. This provided us with an exquisite picture of the planet, changing in time.”

Weather patterns

Upon analyzing the data, the team noticed variations over time, including shifts in the exoplanet’s hot spot and spectral signatures. The observations hinted at a changing atmosphere, potentially explained by massive cyclones due to temperature differences on the exoplanet.

According to the experts, this research represents a significant step forward in potentially observing weather patterns on exoplanets.

Advanced simulations 

“The high resolution of our exoplanet atmosphere simulations allows us to accurately model the weather on ultra-hot planets like WASP-121 b,” explained Jack Skinner, a postdoctoral fellow at the California Institute of Technology and co-leader of the study. 

“Here we make a significant step forward by combining observational constraints with atmosphere simulations to understand the time-varying weather on these planets.”

Broader implications

Quentin also remarked on the broader implications of their study. Understanding weather on exoplanets is crucial for comprehending the complexity of their atmospheres and, by extension, the search for potentially habitable exoplanets.

“Weather on Earth is responsible for many aspects of our life, and in fact the long-term stability of Earth’s climate and its weather is likely the reason why life could emerge in the first place,” added Quentin. 

“Studying exoplanets’ weather is vital to understanding the complexity of exoplanet atmospheres, especially in our search for exoplanets with habitable conditions.”

The future of exoplanet observation

The team anticipates that future observations, especially with the Hubble and powerful telescopes like Webb, will unveil more about weather patterns on distant exoplanets, potentially leading to discoveries of worlds with stable, habitable climates.

The research marks a significant milestone in our understanding of exoplanetary atmospheres and their dynamic nature, paving the way for future explorations and discoveries in the vast universe.

Image Credit: NASA/ESA 

Video Credit: NASA, ESA, Q. Changeat et al., M. Zamani (ESA/Hubble)

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