JWST looks into the atmosphere of an exoplanet bombarded by stellar radiation

This week, astronomers announced that they have found evidence of chemical reactions in the atmosphere of an exoplanet 700 light-years away from Earth. Researchers using the James Webb Space Telescope have created a detailed chemical portrait of the hot gases swirling around the exoplanet WASP-39b. This “hot Saturn” planet orbits very close to its host star, meaning it has temperatures as high as 1,600 degrees Fahrenheit or 900 degrees Celsius. It is also bloated, with about a quarter of Jupiter’s mass but 1.3 times its size.

Early data on WASP-39b was shared this summer when JWST detected carbon dioxide in its atmosphere—the first time this gas has been detected on a planet outside our solar system. Now, a more detailed picture of its atmosphere has been painted in a series of papers recently published on arXiv, three of which have been accepted for publication in Nature and two of which are under review as part of a program designed to rapidly release observations and data coming from the telescope to scientists around the world. The researchers used three of Webb’s instruments, NIRSpec, NIRCam and NIRISS, to collect spectroscopic information about the planet’s atmosphere.

“We observed the exoplanet with multiple instruments that together cover a wide range of the infrared spectrum and a wealth of chemical signatures inaccessible to JWST,” one of the researchers, Natalie Batalha of the University of California, Santa Cruz, said in a statement. “Data like this is a game changer.”

Over the past decade, astronomy researchers have discovered a plethora of exoplanets, or planets outside our solar system. With more than 5,000 exoplanets confirmed to date, the challenge now is to understand these planets in greater depth. More than just knowing the size or mass of an exoplanet, cutting-edge research is now focused on learning about their atmospheres. And instruments like JWST make it possible to peer into these distant atmospheres in greater detail than ever before.

From NASA: Top left, data from NIRISS show fingerprints of potassium (K), water (H2O), and carbon monoxide (CO).  Top right, data from NIRCam shows an obvious water signature.  Bottom left, data from NIRSpec indicate water, sulfur dioxide (SO2), carbon dioxide (CO2), and carbon monoxide (CO).  Bottom right, additional NIRSpec data reveals all these molecules as well as sodium (Na).

a:hover]:text-gray-63 text-gray-63 dark:[&>a:hover]:text-gray-bd dark:text-gray-bd dark:[&>a]:text-gray-bd [&>a]:shadow-underline-gray-63 [&>a:hover]:shadow-underline-black dark:[&>a]:shadow-underline-gray dark:[&>a:hover]:shadow-underline-gray”>NASA, ESA, CSA, J. Olmsted (STScI)

JWST’s instruments are used to perform a technique called transit spectroscopy. They observe the light coming from the host star as it passes through the planet’s atmosphere. This light is split into different wavelengths, and from this, researchers can see which wavelengths have been absorbed. Different chemicals absorb different wavelengths of light, allowing researchers to determine the composition of the planet’s atmosphere.

The research found that sodium, potassium, carbon monoxide and water vapor were present in the atmosphere, confirming previous findings that WASP-39b has water vapor in its atmosphere. But it also found sulfur dioxide, the first time this molecule has been detected in an exoplanet atmosphere. The finding of these molecules suggests a process similar to that found in Earth’s ozone layer, as sulfur dioxide is formed by chemical reactions in the upper atmosphere caused by the host star’s light.

“This is the first time we’ve seen specific evidence of photochemistry – chemical reactions initiated by energetic starlight – in exoplanets,” said another of the researchers, Shang-Min Tsai from the University of Oxford. “I see this as a really promising prospect for advancing our understanding of exoplanet atmospheres with [this mission].”

With WASP-39 b orbiting so close to its host star, one-eighth the distance between Mercury and the Sun, its study can show how radiation from stars interacts with planetary atmospheres. While radiation can be harmful to life (Earth is shielded from the Sun’s radiation by its magnetosphere, without which the planet could be uninhabitable), it can also play an important role in chemical reactions by creating molecules needed for maintaining a livable atmosphere.

“Planets sculpt and morph by orbiting the host star’s radiation bath,” Batalha said. “On Earth, these transformations allow life to thrive.”

Leave a Reply

Your email address will not be published. Required fields are marked *