The James Webb Space Telescope (JWST) has made a weather report for a distant planet.
The powerful space telescope predicts extreme wind speeds, blistering hot temperatures and blankets of rock clouds for the world, called Wasp-43b. As such, the extrasolar planet, or ‘exoplanet’, shows just how strange alien planets outside the solar system can be.
WASP-43b orbits a star located about 283 light-years from Earth; In fact, it is so close to its star that it completes an orbit around Earth in just about 19 Earth hours. This proximity, equivalent to about 2.1 million kilometers, means that the planet, with a mass of about 1.8 times that of Jupiter and a width of 0.9 times that of the gas giant, is tidally linked to its star, WASP -43. .
So one side of WASP-43b – the day side – is permanently facing the star and is constantly bombarded by radiation, raising the planetary temperature to about 2,300 degrees Fahrenheit (1,250 degrees Celsius). That’s hot enough to melt lead. The other side of the planet – the night side – permanently faces space, resulting in temperatures dropping to a relatively cold 1,110 degrees Fahrenheit (600 degrees Celsius). These properties mean that WASP-43b is classified as a ‘hot Jupiter’ planet.
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The JWST Transiting Exoplanet Early Release Science (JTEC-ERS) team was able to use the telescope’s Mid-Infrared Instrument (MIRI) to classify WASP-43b’s climate and the types of weather it experiences on the day and night sides.
“With the new observing power of JWST, WASP-43b has been revealed in unprecedented detail,” team member Laura Kreidberg, director of the Max Planck Institute for Astronomy (MPIA), said in a statement. ‘We see a complex, inhospitable world, with fierce winds, enormous temperature changes and patchy clouds probably made of rock droplets.
“WASP-43b reminds us of the enormous variety of climates possible on exoplanets and the many ways in which Earth is special.”
WASP-43b was discovered in 2011 due to a dip in light that scientists saw due to WASP-43. This dip occurred when the planet crossed the side of its star and Earth from our perspective. During the transit, scientists also saw that the infrared light the planet emits in response to starlight varied.
The key result of the JWST study of WASP-43b was due to this variation in infrared light, observed between the dayside and nightside of the exoplanet as it orbited its star. In particular, the variations have helped scientists build a map showing how temperatures are distributed across hot Jupiter.
Ultimately, the team discovered that the variation in temperature between the day and night sides of WASP-43b is too large to be seen in an atmosphere without clouds. However, possible clouds above WASP-43b’s surface are likely not water-based, like the clouds that envelop Earth. They wouldn’t even be ammonia clouds like the ones we see around Jupiter. WASP-43b is simply too hot for both. Instead, the clouds of this world could have been made stone.
Vaporized material, such as rock, is transported from the dayside to the nightside of WASP-43b by powerful winds of 5,600 miles per hour (9,000 kilometers per hour). That’s three and a half times faster than the top speed of a fighter jet here on Earth. Once on the night side of the planet, scientists think this material cools and condenses. This means that the thick cloud cover on the night side of WASP-43b is likely composed of droplets of liquid rock that have evaporated on the day side of the planet. To this end, the researchers found that the dayside of WASP-43b appears cloudless.
To determine the composition of WASP-43b’s atmosphere, the team split the observed infrared light into individual wavelengths, creating so-called spectra. Because chemicals and elements absorb and emit light at characteristic wavelengths, they leave ‘fingerprints’ in such spectra.
“With Hubble, we could clearly see that there is water vapor on the dayside. Both Hubble and Spitzer suggested there might be clouds on the nightside,” Taylor Bell, team leader and scientist at NASA’s Ames Research Center, said in the statement. “But we needed more precise measurements from JWST to really map the temperature, cloud cover, winds and more detailed atmospheric composition over the entire planet.”
The JWST study not only found that water vapor is found throughout WASP-43b, both on the hot and cooler sides, but it also allowed the scientists to determine a lack of methane in the planet’s atmosphere. Hot Jupiters are normally expected to produce water and methane on their night side via reactions between hydrogen and carbon monoxide.
The team thinks WASP-43b is deficient in methane because its raging winds move these reacting molecules through the planet’s nightside too quickly, so the molecules can’t react with anything to create methane in detectable amounts. Any small amount of methane created would likely mix with other gases and be quickly transported to the dayside of the planet, where the intense heat destroys it.
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The JWST is not finished with WASP-43b yet. A separate team is currently using the $10 billion telescope’s Near-Infrared Spectrometer (NIRSpec) instrument to conduct a follow-up study of the planet.
Not only should this improve the MIRI temperature map, but these observations should also lead to measurements of gaseous carbon monoxide in WASP-43b’s atmosphere, providing a better overall picture of the chemical composition of this extreme world.
The WASP-43b findings were published April 30 in the journal Nature Astronomy.