NASA’s James Webb Space Telescope has captured the distinctive signature of water in the atmosphere surrounding a hot, fluffy gas giant planet orbiting a distant Sun-like star, along with evidence of clouds and haze.
The observation, which revealed the presence of specific gas molecules based on tiny dips in the brightness of precise light colors, is the most detailed of its kind to date, demonstrating Webb’s unprecedented ability to analyze atmospheres hundreds of light-years away.
While the Hubble Space Telescope has analyzed the atmospheres of numerous exoplanets over the past two decades and captured the first unambiguous detection of water in 2013, Webb’s immediate and more detailed observation takes a giant leap forward in the quest to characterize potentially habitable planets beyond Earth. I was pointing out.
WASP-96 b is one of more than 5,000 confirmed exoplanets in the Milky Way. Located roughly 1,150 light-years away in the southern sky constellation Phoenix, this star represents a kind of gas giant that is directly unprecedented in our solar system. With a mass, less than half that of Jupiter and a diameter 1.2 times larger, WASP-96 b is much fluffier than any planet orbiting our Sun. And at a temperature higher than 1000°F, it’s significantly warmer. WASP-96 b orbits extremely close to its Sun-like star, only one-ninth the distance between Mercury and the Sun, and completes one revolution every 3½ Earth days.
The large size, short orbital duration, fluffy atmosphere, and absence of polluting light from nearby objects in the sky make WASP-96 b an ideal target for atmospheric observations.
On June 21, Webb’s Near-Infrared Imager and Slitless Spectrograph (NIRISS) measured 6.4 hours of light from the WASP-96 system as the planet moved across the star. The result is a light curve showing the overall dimming of the starlight during transit and a transmission spectrum revealing the brightness variation of individual wavelengths of infrared light between 0.6 and 2.8 microns.
The light curve confirms the planet’s predetermined features from other observations (the planet’s presence, size, and orbit), while the transmission spectrum reveals previously hidden details of the atmosphere:
The unmistakable signature of water.
Signs of haze.
Evidence of clouds that were thought to be non-existent based on previous observations.
A transmission spectrum is made by comparing starlight filtered from a planet’s atmosphere as it moves through the star with unfiltered starlight detected when the Earth is near the lead. Researchers can see and measure the abundance of critical gases in a planet’s atmosphere based on the absorption pattern (the positions and heights of the peaks on the graph). Just as humans have unique fingerprints and DNA sequences, atoms and molecules have characteristic wavelengths that they absorb.
The spectrum of WASP-96 b, captured by NIRISS, is not only the most detailed near-infrared transmission spectrum of an exoplanet atmosphere ever caught but covers an extensive range of wavelengths, including visible red light and part of the spectrum. Previously inaccessible from other telescopes (wavelengths longer than 1.6 microns). This part of the spectrum is susceptible to water and other vital molecules such as oxygen, methane, and carbon dioxide, which are not immediately apparent in the WASP-96b spectrum but must be detected on other exoplanets planned for observation by Webb.