Researchers using NASA’s James Webb Space Telescope have uncovered fascinating new details about a distant planet called WASP-39 b.
This planet, located about 700 light-years away from Earth, is tidally locked, meaning one side always faces its star, while the other side is in constant darkness.
A team of scientists, including those from the University of Chicago, used the powerful Webb telescope to study the narrow twilight zone where the day side and night side of the planet meet.
They discovered significant differences in temperature and cloud cover within this boundary.
The twilight boundary is incredibly thin, yet the scientists found that one half of this zone is much hotter than the other half. This temperature difference indicates that powerful winds, moving at thousands of miles per hour, sweep across the boundary.
Néstor Espinoza, an exoplanet researcher at the Space Telescope Science Institute and the lead author of the study, expressed amazement at the ability to detect such small differences.
“It’s really stunning that we are able to parse this small difference out, and it’s only possible due to Webb’s sensitivity,” he said.
Maria Steinrueck, a co-author from the University of Chicago, highlighted the importance of this discovery. “This is a whole new level of detail. Previously, we could only get averages of both planet sides.
But there could be so much variation in this small region—temperature, clouds, and atmospheric composition—and we can learn so much more by being able to measure the difference,” she explained.
WASP-39 b is too small and far away to be directly seen, even with the Webb telescope. Instead, scientists analyzed the starlight filtered through the planet’s atmosphere as it moved in front of the star, comparing it to the unfiltered starlight detected when the planet was beside the star. This technique revealed details about the planet’s temperature, composition, and other properties.
The analysis showed that one part of the twilight boundary, known as the “evening” region, is hotter than the other part, known as the “morning” region. This difference is about 300 degrees Fahrenheit (200 degrees Celsius). The winds on WASP-39 b move from the night side across the morning zone, around the day side, and then across the evening zone, creating this temperature variation.
Interestingly, the team also found that the morning region has more cloud cover than the evening region. This was surprising because current models did not predict such a large difference.
Steinrueck commented on this unexpected finding: “The difference in cloud cover was especially interesting because no one had predicted such a large difference for this planet based on our current models.”
The team’s findings have been published in the journal Nature. Researchers plan to use the same methods to study atmospheric differences in other similar tidally locked planets in future observations.
This exciting discovery opens up new possibilities for understanding the complex atmospheres of distant worlds, shedding light on the dynamic processes at play in these exotic environments.
