NASA’s James Webb Space Telescope has marked another first in its release of stunning images: a molecular and chemical portrait of the skies of a distant world.
The telescope’s array of highly sensitive instruments was trained on the atmosphere of a “hot Saturn”, a planet about as massive as Saturn orbiting a star about 700 light-years away, known as the name of WASP-39 b.
While JWST and other space telescopes including Hubble and Spitzer have previously revealed ingredients isolated from this scorching planet’s atmosphere, the new readings provide a full menu of atoms, molecules and even signs of active chemistry. and clouds.
The latest data also gives an idea of what those clouds might look like up close: fragmented rather than a single uniform blanket over the planet.
The results bode well for the ability of the JWST instruments to conduct the wide range of investigations of exoplanets – planets around other stars – hoped for by the scientific community. This includes probing the atmospheres of smaller rocky planets like those in the TRAPPIST-1 system.
The suite of findings is detailed in a set of five new scientific papers ready for publication and available on the Arxiv preprint server (one, two, three, four, five).
Moment “wow”
Among the unprecedented revelations is the first detection in an exoplanetary atmosphere of sulfur dioxide, a molecule produced from chemical reactions triggered by high-energy light from the planet’s parent star. On Earth, the protective ozone layer in the upper atmosphere is created in the same way.
“We now have the first indisputable evidence that photochemical reactions occur in the upper atmospheres of hot giant planets around other stars. The detection of sulfur dioxide was a ‘wow!’ moment, from when we saw the early JWST data, there was a little ‘bump’ that we didn’t know how to explain,” says Ryan MacDonald, a University of Michigan astronomer and co-author of the paper examining sulfur dioxide in the atmosphere of WASP-39b.
“But when we observed WASP-39 b multiple times with JWST, that pesky mysterious signal just wouldn’t go away. Once we saw it with multiple different instruments, we knew we had found something real and Special.
This has led to another first: scientists applying computer models of photochemistry to data that requires physics of this higher level to be fully explained.
“This is the first time we’ve seen concrete evidence of photochemistry – chemical reactions initiated by energetic starlight – on exoplanets. I see this as a really promising prospect for advancing our understanding of exoplanet atmospheres with JWST,” says Shang-Min Tsai, a researcher at Oxford University in the UK and lead author of the paper explaining the origin of sulfur dioxide in WASP-39 b.
In search of life
The resulting improvements in modeling will help develop the technological know-how to interpret potential signs of life in the future. At an estimated temperature of 1,600 degrees Fahrenheit (900 degrees Celsius) and an atmosphere composed mostly of hydrogen, WASP-39b would not be habitable. But the new work points the way to finding evidence of potential life on a habitable planet.
The planet’s proximity to its host star – eight times closer than Mercury is to our sun – also makes it a laboratory for studying the effects of host star radiation on exoplanets. A better knowledge of the star-planet connection should lead to a better understanding of how these processes create the diversity of planets observed in the galaxy.
Other atmospheric constituents detected by JWST include sodium, potassium and water vapor, confirming previous observations from space and ground-based telescopes as well as the search for additional water features at longer wavelengths that do not have never been seen before.
JWST also saw carbon dioxide at higher resolution, providing twice as much data as reported from its previous observations. During this time, carbon monoxide was detected, but obvious signatures of methane and hydrogen sulfide were missing from the JWST data. If present, these molecules occur at very low levels, an important finding for scientists doing inventories of exoplanet chemistry to better understand the formation and development of these distant worlds.
“Since SO2 is an important molecule on rocky planets (and is commonly produced by volcanoes on Earth), learning to detect it in the atmospheres of giant exoplanets prepares us to search for this molecule on terrestrial planets – like lava worlds. — in the years to come,” says MacDonald, also a NASA Sagan Fellow in the University of Michigan’s Department of Astronomy.
Capturing such a broad spectrum of WASP-39b’s atmosphere was the result of an international team with hundreds of independent analyzes of data from four of JWST’s finely calibrated instrument modes. They then performed detailed comparisons of their findings, producing even more scientifically nuanced results. MacDonald participated in the atmospheric modeling of WASP-39b, independently concluding that the mysterious signal was sulfur dioxide. Once he released his results, he saw that they agreed with the other researchers on the team.
beyond human eyes
JWST views the universe in infrared light, at the red end of the light spectrum beyond what human eyes can see; which allows the telescope to pick up chemical fingerprints that cannot be detected in visible light.
To see the light from WASP-39 b, JWST tracked the planet as it passed in front of its star, allowing some of the star’s light to filter through the planet’s atmosphere. Different types of chemicals in the atmosphere absorb different colors from the spectrum of starlight, so the missing colors tell astronomers which molecules are present.
Having such a comprehensive list of chemical ingredients in an exoplanet atmosphere also gives scientists insight into the abundance of different elements relative to each other, such as carbon-oxygen or potassium-oxygen ratios. This, in turn, provides insight into how this planet – and possibly others – formed from the disc of gas and dust surrounding the parent star in its early years.
The chemical inventory of WASP-39b suggests a history of collisions and mergers of smaller bodies called planetesimals to create a possible goliath of a planet. By analyzing an exoplanet’s atmosphere so precisely, JWST’s instruments have exceeded scientists’ expectations and promise a new phase of exploration among the wide variety of exoplanets in the galaxy.
“This suite of papers provides observational evidence for a long-held theoretical prediction that gas giant exoplanets in close orbit undergo exotic chemical reactions, driven by UV light, in their upper atmospheres,” MacDonald says. “Seeing a sulfur-containing gas for the first time in an exoplanet atmosphere in our very first try with JWST demonstrates that this new observatory is about to rewrite all the textbooks on planets around other stars.”
Source: University of Michigan
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