The James Webb Telescope reveals in detail the steamy atmosphere of a distant planet

The light spectrum - which contains information about the composition of a planetary atmosphere 1,150 light-years away - reveals a clear signature of water * The strength of the signal Webb detected hints at the significant role the telescope will play in the search for potentially habitable planets in the coming years

NASA's James Webb Space Telescope captured the distinct signature of water, along with evidence of clouds and haze, in the atmosphere surrounding a hot, gas-bloated giant star orbiting a distant Sun-like star.

The observation, which reveals the presence of specific gas molecules based on tiny drops in the brightness of precise light colors, is the most detailed of its kind to date, and demonstrates Webb's unprecedented ability to analyze atmospheres hundreds of light-years away.

While the Hubble Space Telescope has analyzed the atmospheres of many exoplanets over the past two decades, photographing the first clear detection of water in 2013, Webb's immediate and more detailed observation marks a giant leap in the quest to characterize planets that might be suitable for life beyond Earth.

WASP-96 b is one of more than 5,000 planets discovered in the Milky Way. Located about 1,150 light-years away in the constellation Phoenix in the southern sky, it represents a type of gas giant that has no directly comparable planet in our solar system. With a mass less than half that of Jupiter and a diameter 1.2 times larger than the largest planet in the Solar System, WASP-96 b is far more bloated than any planet orbiting our Sun. And with a temperature higher than 1000 degrees Celsius, it is significantly hotter. WASP-96 b is very close to its Sun-like star, only one-ninth the distance between Mercury and the Sun, and completes one orbit every three and a half Earth days.

The combination of its size, short orbital period, puffy atmosphere and lack of contaminating light from nearby sky objects makes WASP-96 b an ideal target for atmospheric observations.

12 days of filming instead of months at Hubble's

At 21 in June, The Near-Infrared Imager and the Slotless Spectrograph (NIRISS) of Webb measured light from the WASP-96 system for 6.4 hours as the planet moved across the star. The result is light curve showing the overall dimming of the star's light during the transit, and broadcast spectrum which reveals the change in brightness of individual wavelengths of infrared light between 0.6 and 2.8 microns.

While the light curve confirms features of the planet already determined from other observations – the planet's existence, size and orbit – the transmission spectrum reveals previously hidden details of the atmosphere: the unmistakable signature of water (gaseous of course), signs of haze and evidence of clouds that could not have been find out based on previous observations.

A transmission spectrum is created by comparing the starlight filtered through the planet's atmosphere as it moves past the star to the unfiltered starlight. Researchers are able to identify and measure the composition of key gases in a planet's atmosphere based on the absorption pattern - the locations and heights of peaks in the graph. In the same way that people have fingerprints and unique DNA sequences, atoms and molecules have characteristic patterns of 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 exoplanetary atmosphere yet captured, but it also covers a remarkably wide range of wavelengths, including visible red light and some previously inaccessible spectrum Other telescopes (wavelengths longer than 1.6 microns). This part of the spectrum is particularly sensitive to water, as well as other key molecules such as oxygen, methane and carbon dioxide, which were not immediately detected in WASP-96 b's spectrum but should be detectable in other exoplanets planned for future observation by Webb.

Researchers will be able to use the spectrum to measure the amount of water vapor in the atmosphere, limit the amounts of different elements such as carbon and oxygen, and estimate the temperature of the atmosphere at different altitudes. They can then use this information to draw conclusions about the planet's overall composition, as well as how, when and where it formed. The blue line on the graph is a best-fit model that takes into account the data, the known properties of WASP-96 b and its star (eg, size, mass, temperature), and the estimated properties of the atmosphere.

The exceptional detail and clarity of these measurements is possible thanks to the innovative design of the web. The 270 square meter gold-plated mirror efficiently collects infrared light. Its precise spectrographs disperse the light into rainbows of thousands of infrared colors. Its sensitive infrared detectors measure extremely subtle differences in brightness. NIRISS is able to detect a frequency difference of about 50 microns, and differences in brightness of a few hundred parts per million.

In addition, Webb's extreme stability and its orbital position around the Lagrange 2 point about a million kilometers away from the polluting effects of Earth's atmosphere create a continuous view and clean data that can be analyzed relatively quickly.

The extraordinarily detailed spectrum—made by simultaneous analysis of 280 individual spectra captured during the observation—provides just a hint of what Webb has to offer the study of exoplanets. Over the next year, the researchers will use in spectroscopy To analyze the surfaces and atmospheres of several dozen planets- from small rocky planets Committee Giants rich in gas and ice. Almost a quarter of the observation time of Webb's cycle 1 https://www.stsci.edu/jwst/science-execution/approved-programs/cycle-1-go Assigned to the study of planets outside the solar system and the materials that make them up. This research could point to planets where life may have developed, since certain chemical compounds are created, as far as we currently know, only by animals.

This NIRISS observation demonstrates that Webb has the power to characterize the atmospheres of exoplanets – including those of potentially habitable planets – in exquisite detail.

Image credit: NASA, ESA, CSA and STScI

to writee on the NASA website

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