Sunday, November 27, 2022

James Webb Space Telescope Focuses on Exoplanet Atmosphere

Astronomers will be expecting cloudy skies when the James Webb Space Telescope (JWST or Webb) turns its attention to exoplanet atmospheres laden with vaporized rock and crystals such as corundum and perovskite, which form gems on Earth.

Hot Jupiters, which are gas giants orbiting very close to their stars, become so hot that rocky elements, minerals and metals can exist as vapor in their atmospheres, reaching highs of 3,600 Fahrenheit (2,000 °C). scorched by the temperature.

“On Earth, many of these minerals are gems,” Tiffany Kataria, an exoplanet scientist at NASA’s Jet Propulsion Laboratory, said in a statement. space, Thursday (18/8/2022).

“A geologist would study them as rocks on Earth, but they can form clouds on exoplanets. It’s very wild,” he said.

Such minerals have already been detected in the atmosphere of exoplanets. In 2017 astronomers using the Very Large Telescope (VLT) at the European Southern Observatory in Chile detected a titanium oxide signature in the atmosphere of hot Jupiters called WASP-19b. Three years later, the VLT observed daytime iron vapor of the hot Jupiter WASP-76b.

Many hot Jupiters are hot tidally locked, meaning they always show the same face to their star, making their days very hot. In the case of WASP-76b, daytime temperatures reached 4,000 degrees Fahrenheit (2,200 degrees Celsius). The night side of the planet is ‘only’ 2,700 °F (1,500 °C), but it is cold enough that the iron can condense and precipitate as a rain of molten metal.

Previously, these elements and minerals have been detected as a diffuse presence in exoplanetary atmospheres. Now, JWST’s high-resolution vision will be able to directly distinguish these minerals as clouds, measuring their composition spectroscopically.

“Clouds tell us a lot about the chemistry in the atmosphere,” says Kataria.

“It then becomes a question of how clouds form, and the formation and evolution of the entire system,” he said.

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For example, the titanium oxide in WASP-19b absorbs heat, causing temperature reversals in which the planet’s upper atmosphere is warmer than the lower atmosphere, where the opposite would typically be expected.

JWST is observing the alien atmosphere, detecting clouds of water in the atmosphere of exoplanet WASP-96b, where scientists previously thought there were no clouds. During its first year of observation, JWST also investigated several other exoplanetary atmospheres.

Kataria has been involved in a number of projects, including using JWST’s Near Infrared Spectrometer (NIRSpec) in collaboration with MIT’s Thomas Mikael-Evans to characterize the atmosphere of the ultra-hot Jupiter WASP-121b, which is 850 light-years from Earth. is far. The first exoplanet from Earth and with an aquatic stratosphere was found.

Another Kataria project with JWST is to observe the hot Jupiter HD 80606b, which lies 290 light-years from Earth and is in a highly eccentric orbit around its star, taking it as close as 2.8 million miles (4.5 million kilometers). going and traveling. 81 miles (131 million km).

As a result, HD 80606b undergoes ‘flash heating’ as its temperature rises from 930 °F (500 °C) to 2,200 °F (1,200 °C) within a few hours as it approaches its star. The effects on the planet’s weather are staggering, with computer models predicting storms and gusty winds up to 15 times the speed of sound; Kataria hopes that JWST can witness the event.

Finally, Kataria led a joint project with Brian Kilpatrick of the Space Telescope Science Institute in Baltimore to create a 3D ‘Eclipse Map’ of exoplanet HD 189733b with JWST’s Mid-Infrared Instrument (MIRI). An eclipse map is created when a planet moves behind its star.

As the planet enters the eclipse, by subtracting the faint signature of the planet’s light from that of the stars, scientists can isolate the planet’s light and map its atmospheric temperature. Kataria and Kilpatrick hope the technique will allow them to determine the most accurate circulation model for an exoplanet’s atmosphere.

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This exoplanet, which is 64.5 light-years away from Earth, was discovered in 2005 and has since become one of the best-studied hot Jupiters. Several other projects will also observe HD 189733b with JWST, including an in-depth survey of the molecular composition of the planet’s atmosphere and efforts to determine the composition of any clouds present, as well as attempts to search for vaporized mineral aerosols. is included. Clouds form in HD 189733b’s atmosphere.

The atmospheres of smaller, rockier exoplanets will also be monitored by JWST. The researchers will measure the composition of the atmosphere at 55 Cancri e, a super-Earth with eight times the mass of our planet; Scientists are also hoping to determine whether the lava is hot enough to rain. And the TRAPPIST-1 system’s seven worlds will also be observed, with JWST surveying every planet in the system for atmospheres.

Astronomers will pay close attention to TRAPPIST-1e, the most Earth-like planet in the neighborhood. If it is habitable, evidence could be found in the atmosphere, including clouds.

“Clouds are an important feature on Earth for controlling temperature,” says Kataria.

“They’re an important consideration for Earth’s climate. It makes sense that clouds could also be an important component of a habitable exoplanet’s atmosphere. The more we understand how clouds form in general — as They do on Earth and other planets in the Solar System — the more we understand how clouds evolved in more exotic environments.”

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