The exoplanet in question is WASP-39b, a gas giant roughly the size of Saturn orbiting close to its star about 700 light-years from Earth. Scientists have studied WASP-39b in the past using the Hubble and Spitzer Space Telescopes to determine water in an exoplanet’s atmosphere in 2018, while Webb detected carbon monoxide on the planet in August.
But the new Webb observations released Tuesday are a broader, more detailed view of WASP-39b’s atmosphere, and even provide clues about how such a large planet ended up orbiting much closer to its star than Mercury to our sun. Moreover, the new results achieve the overarching goal of the Webb Early Release Science Program, which has been to test and prove what a groundbreaking new space telescope is really capable of.
“Without this software, we probably wouldn’t have been able to perform this kind of detailed analysis on a single planet as quickly and efficiently as we have,” Adina Feinstein, a University of Chicago graduate student and lead author of an upcoming paper on Webb’s new findings, says. inverse. “And the accuracy we get is kind of beyond our wildest dreams.”
what’s new – While previous studies had identified water and carbon dioxide in WASP-39b’s atmosphere, the new research revealed a wide range of chemicals. Water vapor and carbon dioxide have been found, but also carbon monoxide, sodium, potassium and, most importantly, sulfur dioxide, which had not been detected before in the atmosphere of an exoplanet.
“The really interesting thing about sulfur dioxide is that the only way you can get that into the planetary atmosphere is through a process called photochemistry,” says Feinstein. “So this is one of the first pieces of evidence we have for the interaction between stars and planets, where because a planet is so close to its star, and it gets so intensely irradiated, you can get these kinds of species formed.”
She adds that the findings also help explain how WASP-39b entered an orbit so close to its star. Webb’s new data shows a low carbon-to-oxygen ratio in an exoplanet’s atmosphere, meaning there are much more oxygen-containing molecules, such as water vapor, than carbon-containing molecules, such as methane, not seen at all in the new observations. .
Because carbon-containing molecules tend to accumulate more on planets when they are farther from the star, according to Feinstein, and less carbon accumulated if that planet migrated close to a star, scientists now believe that WASP-39b formed very far from its star, rather than in Anywhere close to where it is today in its very short orbital duration, then migrated inward,” she says.
Despite Webb’s power, it cannot image a planet as far away as WASP-39b, and instead detects information carried by its star’s light as it passes through an exoplanet’s atmosphere as the planet passes in front of its star from Webb. vantage point. But this information offers more than the chemical signatures of WASP-39b’s atmosphere; It could also help scientists paint a picture of what an exoplanet would look like if humans could visit it. Evidence from the new Webb data suggests, for example, that WASP-39b has what are known as patchy clouds around the planet’s separator, which is very similar to what we see here on Earth, where we have regions with lots of clouds and regions without, Feinstein says. Lots of clouds.” This is the first tentative evidence of this type of cloud structure on an exoplanet.”
The results are detailed in five papers that are still being published, but are publicly available on the academic preprint server arxiv.org.
How did they do it? – The new meteorological basics of WASP-39b are tried and true: Scientists point a telescope at a distant star and wait for an exoplanet to pass between the star and the telescope, “passing” the star. The dip in star brightness caused by an exoplanet transit is one of the methods exoplanet hunters use to find these alien worlds in the first place, but scientists can also study those exoplanets by observing starlight passing through a planet’s atmosphere during the transit. .
Webb can ship such observations of the exoplanet’s atmosphere thanks to the huge size and power of the new telescope. With a primary mirror 21 feet in diameter, compared to Hubble’s eight-foot mirror, and Spitzer’s 2.8-foot mirror, Webb can simply gather and amplify more light, seeing and revealing more.
But the record-breaking optics are only part of the story. Webb’s exquisitely tuned instruments, which were put through their paces as part of the Science Early Release program, were able to parse information out of the reach of Hubble and Spitzer and out of focus.
It was the Near Infrared Imager and Slit Spectrometer, or NIRISS instrument, for example, that discovered the carbon-to-oxygen ratio that tells astronomers much about the origins of WASP-39b.
“Hubble didn’t have the resolution we needed to be able to resolve this feature,” Feinstein says.
Meanwhile, it was Webb’s Near Infrared Spectrometer, or NIRSpec, that detected sulfur dioxide that illustrates the active photochemistry occurring on WASP-39b.
Spectrometers like NIRSpec and NIRISS break down light into wavelengths, and since scientists know which molecules absorb light at different wavelengths, the resulting spectrum tells scientists what molecules are or aren’t in the exoplanet’s atmosphere. It turns out that specializing in observing infrared light, which Webb does, is better for this kind of extrasolar spectrometry than a more general telescope like the Hubble, which monitors ultraviolet, visible, and some infrared.
So far, Webb’s early observations have ended up surprising scientists like Feinstein.
“We had to go back and forth between whether or not we believed the data, or whether we believed our old models,” she says.
What’s Next – As part of the Early Release Science program, the new findings are intended to help scientists predict what they can expect from Webb in the coming years.
In the short term, according to Feinstein, that means more research papers on WASP-39b and other exoplanets will come out of the Early Release Science program’s data. Then there are also the observations of exoplanets now taking place as part of Webb’s first year of official science observations, Cycle 1, which includes fantastic worlds like the TRAPPIST-1 planets, small, rocky worlds 40 light-years from Earth.
In the long term, these observations will grow more detailed, helping scientists understand the true extent of the diversity of worlds beyond our solar system, and thus helping us understand our place in the universe.
“We’re really starting to get a sense of the demographics of what the atmospheres of exoplanets look like,” says Feinstein. “It really is like the dawn of a new era for exoplanet atmospheres.”