By Pranjal Malewar 25 Sep, 2024
Collected at: https://www.techexplorist.com/glimpse-uniquely-inflated-asymmetric-exoplanet/90169/
Due to how their air moves, the atmospheric conditions of hot exoplanets are expected to change between morning and evening. Ground-based observations at high detail have found this difference in several ultra-hot exoplanets (over 2,000 K), but it’s unclear how common this is among all exoplanets.
Astronomers from the University of Arizona and an international team studied the atmosphere of a hot, unusually large exoplanet- WASP-107b – using NASA’s James Webb Space Telescope. This exoplanet is the size of Jupiter but only a tenth of its mass. They found that its atmosphere has east-west asymmetry, meaning there are significant differences between the two sides.
WASP-107b has a temperature of about 890 degrees Fahrenheit, which is between the temperatures of the planets in our solar system and the hottest known exoplanets.
Lead study author Matthew Murphy, a graduate student at the U of A Steward Observatory, said, “This is the first time the east-west asymmetry of any exoplanet has ever been observed from space as it transits its star. A transit is when a planet passes in front of its star—like the moon does during a solar eclipse.”
“I think observations made from space have a lot of different advantages versus observations made from the ground.”
East-west asymmetry in an exoplanet means there are differences in atmospheric features, like temperature or clouds, between its eastern and western sides. Finding this asymmetry is important for understanding exoplanets’ climate, atmospheric dynamics, and weather patterns—planets outside our solar system.
The exoplanet WASP-107b is tidally locked to its star, which means it always shows the same side to the star. One side of the planet is in permanent daylight, while the other side is always in darkness.
Along with the James Webb Space Telescope, the team used the transmission spectroscopy technique to gain insights into what makes up the atmospheres of other planets. The telescope captured a series of images as the planet moved before its star, gathering information about its atmosphere.
Using advanced techniques and the high precision of the James Webb Space Telescope, researchers could distinguish the signals from the planet’s eastern and western sides, allowing for a closer examination of specific processes in its atmosphere.
Murphy said, “These snapshots tell us a lot about the gases in the exoplanet’s atmosphere, the clouds, the structure of the atmosphere, the chemistry, and how everything changes when receiving different amounts of sunlight.”
“The exoplanet WASP-107b is unique in that it has a very low density and relatively low gravity, resulting in an atmosphere that is more inflated than other exoplanets of its mass would be.”
“We don’t have anything like it in our own solar system. It is unique, even among the exoplanet population.”
Murphy said, “Traditionally, our observing techniques don’t work as well for these intermediate planets, so there’s been a lot of exciting open questions that we can finally start to answer. For example, some of our models told us that a planet like WASP-107b shouldn’t have this asymmetry at all – so we’re already learning something new.”
Thomas Beatty, study co-author and an assistant professor of astronomy at the University of Wisconsin-Madison, said, “Researchers have been looking at exoplanets for almost two decades, and many observations from both the ground and space have helped astronomers guess what the atmosphere of exoplanets would look like.”
“But this is the first time that we’ve seen these types of asymmetries directly in the form of transmission spectroscopy from space, which is the primary way in which we understand what exoplanet atmospheres are made of – it’s actually amazing.”
Murphy and his team are analyzing the collected data and plan to conduct more detailed observations of the exoplanet to understand what causes the east-west asymmetry.
Murphy said, “For almost all exoplanets, we can’t even look at them directly, let alone be able to know what’s going on one side versus the other. For the first time, we’re able to take a much more localized view of what’s going on in an exoplanet’s atmosphere.”
Journal Reference:
- Murphy, M.M., Beatty, T.G., Schlawin, E. et al. Evidence for morning-to-evening limb asymmetry on the cool low-density exoplanet WASP-107 b. Nat Astron (2024). DOI: 10.1038/s41550-024-02367-9
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