By: Vijay Gopal
August 5th, 2022
NASA’s James Webb Space Telescope has detected evidence of water along with indications of clouds and haze, in the atmosphere of a hot, puffy gas
giant planet along the orbit of a far away sun-like star. Illustration by Engine House
The planet, WASP-96b is one of more than 5,000 confirmed exoplanets in the Milky Way. It’s located approximately 1,150 light-years away in the constellation of Phoenix in the southern-sky. WASP-96b is puffier than any planet orbiting our sun, with a mass less than half that of Jupiter and a diameter 1.2 times greater. With a temperature greater than 1000°F, it is considerably hotter.
WASP-96b orbits extremely close to its Sun-like star, just one-ninth of the distance between Mercury and the Sun, completing one circuit every 3½ Earth-days according to NASA.
On June 21, Webb's Near-Infrared Imager and Slitless Spectrograph (NIRISS) measured light from the WASP-96 system for 6.4 hours as the planet moved across the star. This resulted in a light curve showing the overall dimming of starlight during the transit, and a transmission spectrum revealing the brightness change of individual wavelengths of infrared light between 0.6 and 2.8 microns.
The light curve confirmed the existence, size, and orbit of the planet, which had already been determined by other observations. The transmission spectrum revealed previously unknown details about the atmosphere, such as the unambiguous signature of water, indications of haze, and evidence of clouds that were previously thought not to exist based on previous observations.
A transmission spectrum is created by comparing starlight filtered through the atmosphere of a planet as it moves across the star to unfiltered starlight detected when the planet is beside the star. Based on the absorption pattern — the locations and heights of peaks on the graph, researchers can detect and measure the abundances of key gases in a planet's atmosphere. Similarly to how people have unique fingerprints and DNA sequences, atoms and molecules have distinct patterns of wavelengths that they absorb.
WASP-96b's spectrum is not only the most detailed near-infrared transmission spectrum of an exoplanet atmosphere ever captured, but it also covers a remarkably wide range of wavelengths, including visible red light and a portion of the spectrum not previously accessible from other telescopes, according to NASA.
Over time, measurements like these should help us understand the birth of gas giant planets like WASP-96b — and our own Saturn and Jupiter, as well — during the formation of star systems, clock climate patterns sweeping around them and, just maybe, for smaller worlds, enable searches for signs of life.
References:
Garner, Rob. “NASA's Webb Reveals Steamy Atmosphere of Distant Planet in Detail.” NASA, NASA, 11 July 2022, www.nasa.gov/image-feature/goddard/2022/nasa-s-webb-reveals-steamy-atmosphere-of-distant-planet-in-detail.
Sokol, Joshua. “First Look: The Exoplanet Wasp-96b.” The New York Times, The New York Times, 12 July 2022, www.nytimes.com/2022/07/12/science/wasp-96b-exoplanet-webb-telescope.html.
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