NASA’s James Webb Space Telescope has captured the first clear evidence of carbon dioxide in the atmosphere of an exoplanet. The exoplanet is a gas giant orbiting a sun-like star about 700 light-years away. This discovery will provide important information about the composition and formation of the planet. The discovery will soon be published in the journal Nature and provides evidence that in the future, James Webb will be able to detect and measure carbon dioxide in the thin atmospheres of smaller, rocky planets.
WASP-39 b is a hot gas giant planet and has about one-quarter the mass of Jupiter (almost the same mass as Saturn), but is 1.3 times larger in diameter than Jupiter. Its swelling is partly due to its high temperature — about 900 degrees Celsius. Unlike the cooler, compact gas giants in the Solar System, WASP-39 b orbits its parent star at a fairly close distance—about one-eighth the distance between Mercury and the Sun; It takes just four days to go around. This planet was discovered in 2011 by ground-based telescopes, using the transit method. As the planet passes between the star and us as it orbits its star, it causes periodic dimming of its light. Astronomers call this event a transit.
Previous observations, including those by NASA’s Hubble and Spitzer Space Telescopes, have confirmed the presence of water vapor, sodium and potassium in the planet’s atmosphere. Webb’s unique infrared sensitivity has now confirmed the presence of carbon dioxide there.
Transiting planets like WASP-39 b, whose orbits are viewed from the side rather than from above, offer researchers an ideal opportunity to study a planet’s atmosphere.
During the transit, part of the star’s light will be completely obscured by the planet, and part will pass through its atmosphere.
Because different gases absorb different combinations of colors, researchers can study small differences in brightness across wavelengths of the emitted spectrum, and as a result, determine exactly what the atmosphere is made of. Because of its inflated atmosphere and frequent transits, WASP-39 is an ideal target for emission spectroscopy.
First clear detection of carbon dioxide
To observe WASP-39, the researchers used the Webb Near-Infrared Spectrograph (NIRSpec). In the resulting spectrum of an exoplanet’s atmosphere, a small bump between 4.1 and 4.6 microns represents the first clear, detailed evidence of carbon dioxide ever observed on a planet outside the Solar System.
“As soon as the data appeared on my screen, I was greeted by a huge feature of carbon dioxide. It was a special moment that crossed an important boundary in exoplanetary science,” says Zafar Rustamkulov, a member of the research group.
No other observatory has ever measured such small differences in the brightness of so many individual colors in the 3-5.5 micron range of an exoplanet’s emission spectrum. Access to this part of the spectrum is crucial for measuring gases such as water vapor, methane, and carbon dioxide—which are thought to exist on many different types of exoplanets.
According to team leader Natalie Bathala, a researcher at the University of California, Santa Cruz, the detection of such a clear signal of carbon dioxide on WASP-39 b is a sign that we will also detect the atmospheres of small, Earth-sized rocky exoplanets.
Studying the composition of the planet’s atmosphere is important from the point of view that it provides information about the origin and formation of the planet.
According to researchers, carbon dioxide molecules are highly sensitive witnesses of planet formation. By measuring the properties of carbon dioxide, in the future, we will be able to determine how much solid and how much gaseous matter was used in the formation of this gas giant planet. Over the next decade, the James Webb Space Telescope will make such measurements on many different planets and provide detailed information on planet formation; This in turn will tell us how unique our solar system is or isn’t.
Prepared from nasa.gov.