Webb details the planet’s humid atmosphere

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NASA’s James Webb Space Telescope has detected the signature of water, along with evidence of clouds and haze, in the atmosphere of a hot, puffy gas giant planet orbiting in the distance around a Sun-like star.

Webb shows in detail the vaporous atmosphere of a planet in space. Credit: NASA, ESA, CSA, and STScI

The study, which identifies the presence of certain gas molecules based on minute dips in the brightness of certain hues of light, is the most detailed of its kind to date and demonstrates the Webb telescope’s unparalleled ability to study atmospheres. hundreds of light years away.

While the Hubble Space Telescope has analyzed many exoplanet atmospheres over the past two decades, capturing the first clear detection of water in 2013, Webb’s immediate and more detailed observation represents a significant step forward in the quest to characterize potentially habitable planets beyond Earth.

WASP-96 b is one of more than 5,000 extrasolar planets identified in the Milky Way. It is located about 1,150 light-years away in the constellation Phoenix in the southern sky and represents a form of gas giant that has no direct equivalent in our solar system.

WASP-96 has a mass less than half that of Jupiter and a diameter 1.2 times larger than any other planet orbiting our Sun. And with temperatures above 1,000°F, it is considerably warmer. WASP-96 b orbits its Sun-like star incredibly close, just one-ninth the distance between Mercury and the Sun, and completes one circuit every 312 Earth days.

WASP-96b is a suitable target for atmospheric studies due to its massive size, short orbital period, dense atmosphere, and lack of light contamination from surrounding objects.

On June 21, the NIRISS (Near-Infrared Imager and Slitless Spectrograph) aboard the James Webb Space Telescope measured light from the WASP-96 system for 6.4 hours, as the planet passed the star. The result is a light curve describing the overall attenuation of starlight during transit, along with a transmission spectrum displaying the change in brightness of distinct infrared wavelengths between 0.6 and 2.8 microns.

The transmission spectrum shows newly unknown elements of the atmosphere, including the unmistakable signature of water, signs of haze and evidence of clouds that were previously thought to be non-existent based on past observations.

A transmission spectrum is created by comparing starlight filtered by a planet’s atmosphere as it passes through a star to the unfiltered starlight observed when the planet is in close proximity to the star.

Based on the absorption pattern – the locations and heights of the peaks in the graph – researchers can detect and analyze the abundances of essential gases in a planet’s atmosphere. Just as humans have unique fingerprints and DNA sequences, atoms and molecules absorb light in their own unique patterns.

The spectrum of WASP-96 b captured by NIRISS is not only the most detailed near-infrared transmission spectrum of an exoplanet’s atmosphere captured to date, but it also covers a remarkable range of wavelengths, including visible red light and part of the spectrum that other telescopes have not been able to access (wavelengths greater than 1.6 microns).

This part of the spectrum is particularly sensitive to water and other important chemicals such as oxygen, methane and carbon monoxide, which are not immediately visible in the WASP-96 b spectrum, but which should be observable on other exoplanets targeted by Webb’s research.

Using the spectrum, scientists will be able to quantify the amount of water vapor in the atmosphere, restrict the abundance of various elements such as carbon and oxygen, and estimate the temperature of the atmosphere as a function of depth.

They can then use this data to draw conclusions about the overall composition of the planet, as well as how, when and where it formed. The blue line on the graph is the best-fitting model, which takes into account the data, known characteristics of WASP-96b and its host star (e.g., size, mass, and temperature), and properties assumed atmospherics.

The excellent clarity and accuracy of these measurements are made possible by Webb’s cutting-edge design. Its 270 square foot gold-coated mirror effectively collects infrared light.

Its precise spectrographs scatter light into hundreds of colors of the infrared rainbow. And its sensitive infrared detectors detect incredibly small changes in luminance. NIRISS can detect color changes as small as one thousandth of a micron (the difference between green and yellow is about 50 microns) and differences in brightness as small as several hundred parts per million.

Additionally, Webb’s extraordinary stability and orbital placement near Lagrange Point 2, about a million miles from the polluting effects of Earth’s atmosphere, allows for an uninterrupted view and data that can be examined very quickly.

The incredibly accurate spectrum, which was created by simultaneously analyzing 280 separate spectra acquired during the observation, provides insight into what Webb has planned for exoplanet exploration.

Next year, scientists will use spectroscopy to study the surfaces and atmospheres of dozens of exoplanets, ranging from small rocky planets to gas- and ice-rich giants. Nearly a quarter of Webb Cycle 1 observing time is spent searching for exoplanets and their building blocks.

This NIRISS image illustrates Webb’s ability to accurately analyze the atmospheres of exoplanets, including potentially habitable planets.

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