by The James Webb Space Telescope (JWST) has discovered methane and water vapor in the atmosphere of a Jupiter-like world located about 163 light-years away.
Astronomers made the discovery by using this powerful infrared space telescope to look at the extrasolar planet or “exoplanet” WASP-80 b pass the face of its red dwarf star, which it orbits around once every 3 Earth days.
Astronomers have seen water vapor in the atmospheres of about a dozen planets so far, but methane – although it is commonly found in the atmospheres of solar system life such as Jupiter, Saturn, Uranus and Neptune – has been detected for a long time using space-based spectroscopy. more rare. That’s what the team, which includes Arizona State University scientists Luis Welbanks and Michael Line from the School of Earth and Space Exploration, and Bay Area Environmental Research Institute (BAERI) researcher Taylor Bell, has now James Webb Space Telescope.
“This was the first time we had seen such a clear methane spectral feature with our eyes in the spectra of a transiting exoplanet, not too dissimilar to what was seen in the spectra of the giant planets of the solar system half a century ago,” Welbanks said in a statement.
To be clear, this is not the first time JWST has detected atmospheric methane. For example, the observatory found such molecules around the exoplanet K12-18b earlier this year.
Related: Hubble Telescope probes nearby exoplanet, finds it’s the size of Earth
A needle in a cosmic haystack
WASP-80 b is classified as a “hot Jupiter” because it is not as close to its parent star as a so-called hot Jupiter, but it is still closer than a so-called cold Jupiter. The original Jupiter, the largest planet in our solar system and the gas giant that gives this category of planets their names, is technically “cold Jupiter.”
Because of this relative proximity, WASP-80 is not a major event as distinguished from its red dwarf star. In fact, it is worth the capabilities of the $10 billion JWST. It is the equivalent of seeing a single human hair from a distance of 9 miles (14.5 kilometers) away.
Fortunately, astronomers have a way to tackle the challenge. They basically wait for WASP-80 b to carry the face of the red dwarf it orbits, then observe a collective spectrum related to the planet.
Because chemical elements and molecules absorb light at specific wavelengths, looking at the combined spectrum and comparing it to the individual spectrum of the star reveals specific fingerprints of specific molecules in a planet’s atmosphere.
“Using the transit method, we observed the system where the planet moved in front of its star from our perspective, causing the star we see to shrink a little. ,” said Welbanks.
“During this time,” continued Welbanks, “there is a thin ring of the planet’s atmosphere around the planet’s day/night boundary illuminated by the star, and certain colors of light where the molecules in the planet’s atmosphere absorb light , the atmosphere breathes. thicker and blocks more starlight, causing a deeper dimming compared to (with) other wavelengths where the atmosphere appears transparent.
“This method helps scientists like us understand what the planet’s atmosphere is made of by seeing the colors of light that are blocked,” explained the researcher.
But the team didn’t stop there. The scientists used another method to measure WASP-80’s atmosphere as well.
You’re getting hotter … while hunting methane
Like all planets, WASP-80 b emits some of its light in the form of thermal radiation. The wavelength category and intensity of this light depends on the temperature of the planet.
This proximity of WASP-80 b to its star gives the planet a surface temperature of 1,025 degrees Fahrenheit (552 degrees Celsius) compared to Jupiter’s normal warm temperature of 2,150 degrees Fahrenheit (1,177 degrees Celsius) and the positively frigid temperatures of our Jupiter at minus 235 degrees Fahrenheit (-148 degrees Celsius).
Jupiter is also hot and tidally locked to its stars, meaning it has permanent warmer “days” that always face the star, and cooler “nights” that always face the space.
Just before WASP-80 claims a star, it is pointed dayside towards Earth, which means that infrared light coming from the planet will be shown as a result of measuring its thermal emission when the light is coming from star during the eclipse. This gives astronomers “eclipse spectra” of light absorption patterns linked to molecules in a planet’s atmosphere. These patterns are visible as a decrease in the light emitted by the planet at specific wavelengths.
The best of both worlds
By combining the eclipse and transit data the team was able to see how much light was both blocked and emitted by WASP-80 b’s atmosphere at different wavelengths. Next, the researchers used two different models to simulate what the atmosphere of a planet like WASP-80 b would look like under the extreme conditions of a hot Jupiter.
One model was rigorous, accounting for existing physics and chemistry to determine the levels of methane and water that could be expected from such a world. The other model was more flexible, trying millions of different combinations of methane and water abundances and temperatures to find the recipe that best fit the data. When transit and eclipse data are compared with the two models the team reached the same, clear conclusion.
They definitely detected methane in the atmosphere WASP-80 b.
“Before JWST, methane was largely undetected, despite the hope that it could be found with the Hubble Space Telescope on planets where it should be abundant,” explained Line. “This lack of detection has generated a flurry of ideas from the intrinsic depletion of carbon to its photochemical destruction to the mixing of deep-depleted methane gases.”
The next step is to explore what the chemical composition of WASP-80 can tell scientists about the exoplanet’s features, formation history and evolution as they relate to methane and water abundances. Such studies would enable the team to infer things like the ratio of atmospheric carbon to oxygen, too. This ratio is something that varies based on exactly where a planet forms around a star; it could reveal if WASP-80 b formed where it is now, or if it was born further out before migrating towards its star.
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The team will also compare Jupiter’s hot atmosphere outside the solar system with the atmospheres of the planets orbiting the sun, using samples and data collected by space missions that have already visited Jupiter and Saturn.
“Methane is not only an important gas for tracing atmospheric composition and chemistry in giant planets but is also hypothesized, in conjunction with oxygen, to be a potential signature of biology,” said Welbanks. “One of the main goals of the Habitable Life Observatory, NASA’s next flagship mission after JWST and Rome, is to look for gases like oxygen and methane in Earth-like planets around similar stars the sun.”
The team’s research was published on 22 November in the journal Nature.
