Astronomers have successfully examined the atmosphere of a hot and unusually inflated exoplanet with the help of NASA’s James Webb Space Telescope.
A team of researchers from the University of Arizona, working alongside an international group, has studied the atmosphere of a hot exoplanet that is distinctively larger in size than Jupiter, yet its mass is only one-tenth of Jupiter’s. They discovered an east-west asymmetry in the planet’s atmosphere, indicating notable variations between the two sides of its atmospheric structure.
The results of this study are published in the journal Nature Astronomy.
“This research marks the first occasion where the east-west asymmetry of an exoplanet has been observed while it passes in front of its star, from a space-based perspective,” stated lead author Matthew Murphy, a graduate student at the University of Arizona’s Steward Observatory. A transit occurs when a planet crosses the path of its star, similar to how the moon obscures the sun during a solar eclipse.
“Observing from space offers numerous advantages compared to ground-based observations,” Murphy explained.
The term east-west asymmetry describes the variations in atmospheric features, such as temperature and cloud formation, between the eastern and western halves of the exoplanet. Understanding whether such asymmetry exists is vital for grasping the climate, atmospheric behavior, and weather systems of exoplanets—those planets situated outside our solar system.
WASP-107b, the exoplanet in question, is tidally locked to its star. This means it consistently presents the same side to the star, resulting in one hemisphere always basking in perpetual daylight while the other is shrouded in permanent darkness.
Murphy and his colleagues employed the transmission spectroscopy method using the James Webb Space Telescope. This technique is essential for astronomers studying the atmospheric composition of distant planets. They captured a series of images as the exoplanet transited its host star, which allowed them to gather information about its atmospheric characteristics. Utilizing advanced methods and the exceptional precision of the James Webb Space Telescope, the team could distinguish between the atmospheric signals of the planet’s eastern and western sides, providing deeper insights into specific processes occurring in its atmosphere.
“These images provide extensive information about the gases present in the exoplanet’s atmosphere, including cloud formations, atmospheric structure, and chemical properties, as well as how these elements vary with different levels of sunlight exposure,” said Murphy.
WASP-107b is particularly noteworthy for its very low density and gravity, leading to an abnormally inflated atmosphere compared to other exoplanets of similar mass.
“There’s nothing else like it in our own solar system. It’s truly one of a kind, even among other known exoplanets,” Murphy remarked.
This exoplanet has a temperature of approximately 890 degrees Fahrenheit, positioning it between the planets in our solar system and the hottest known exoplanets.
“Traditionally, our observational techniques have not been very effective for these intermediate-temperature planets, so there have been many intriguing questions that we can now begin to explore,” said Murphy. “For instance, some of our models suggested that a planet like WASP-107b shouldn’t exhibit such an asymmetry—so we are already uncovering new insights.”
Researchers have been investigating exoplanets for nearly two decades, and numerous observations from both land-based and space-based telescopes have provided astronomers with educated guesses about the atmospheres of these distant worlds, according to Thomas Beatty, a co-author of the study and an assistant astronomy professor at the University of Wisconsin-Madison.
“However, this is the first instance where we’ve directly observed these forms of asymmetries through transmission spectroscopy from space, which is our primary method of understanding exoplanet atmospheres—it’s truly remarkable,” Beatty stated.
Murphy and his team are actively analyzing the observational data they have collected and plan to conduct more detailed examinations of the exoplanet, including additional observations to better understand the forces behind this atmospheric asymmetry.
“For almost all exoplanets, we cannot examine them directly, let alone discern the differences between their sides,” Murphy explained. “For the first time, we are able to gain a localized perspective on what’s taking place in the atmosphere of an exoplanet.”
