The James Webb Space Telescope has once more reported exciting findings. This detection is the first-time carbon dioxide has been spotted around a planet outside the solar system.
An artist’s impression of the exoplanet WASP-39b. Image Credit: NASA, ESA, CSA, and J. Olmsted (STScI)
The James Webb Space Telescope (JWST) has found the first definitive evidence of carbon dioxide around a planet outside the solar system, Wasp-39 b, a gas giant extra-solar planet — or exoplanet — located 700 light-years away from Earth.
The investigation of exoplanet atmospheres can help scientists determine their compositions and the processes that were at play during their formation. This particular result is an early demonstration of the JWST’s ability to investigate even the thin atmospheres of some violently hot worlds outside the solar system.
Carbon dioxide is an important molecule in this research due to the fact that it is a central component of Earth’s atmosphere. This means detecting this molecule could eventually become an important signal of a planet capable of sustaining life.
Thus the detection of carbon dioxide in the atmosphere of WASP-39 b is an important step in the investigation of exoplanets, even though its unlikely life could prosper on this extreme and inhospitable world.
The gas giant exoplanet WASP-39 b has roughly 25 percent the mass of Jupiter but has a diameter 1.3 times that of the solar system’s largest planet.
The exoplanet orbits about eight times closer to its star than Mercury orbits the sun, and this proximity gives WASP-39 b a scorching hot surface temperature of around 900 degrees Celsius. This temperature causes the atmosphere of the exoplanet to ‘puff out.’
The planet — classified as a ‘hot Jupiter’ — completes an orbit of its parent star in little more than four Earth days. From our position, as the exoplanet completes an orbit WASP-39 b crosses — or transits — the face of its star.
Not only was this transit, and the dip in light from its star it causes, the key to discovering the exoplanet in 2011, but because it is edge-on it also allows astronomers to investigate its atmosphere.
How the JWST Investigates Exoplanet Atmospheres
To examine exoplanet atmospheres and their composition the JWST uses its Near-Infrared Spectrograph (NIRSpec) instrument and a technique called ‘transmission spectroscopy.’
This method hinges on the fact that different elements absorb and emit light at characteristic wavelengths. That means that when a planet crosses the face of its star some starlight is filtered through the planet’s atmosphere.
The transmission spectrum of WASP-39b captured by the JWST shows the first definitive evidence of carbon dioxide around an exoplanet. Image Credit: NASA, ESA, CSA, and J. Olmsted (STScI)
The gases in the atmosphere filter out light at certain wavelengths depending on its composition meaning they leave a distinct ‘fingerprint’ on the light from their star. That means by looking at the spectra of the starlight astronomers can tell what gases are in the atmosphere.
WASP-39 b is a great target for transmission spectroscopy due to the fact it makes frequent transits of its star and the fact that the atmosphere is so extended.
What Do We Know About WASP-39 b’s Atmosphere?
Obtaining the spectrum of light passing through the atmosphere of WASP-39 b atmosphere the NIRSpec team spotted a tiny peak between 4.1 and 4.6 microns.
While this may not sound particularly significant, it is clear evidence of carbon dioxide in the hot Jupiter’s atmosphere and marks the crossing of an important milestone in exoplanet science.
Carbon dioxide is an excellent molecule to observe by astronomers who want to trace a planet’s evolution back to its formation. This is because it can be used to determine the ratio of solid to gaseous material that went towards the formation of a gas giant.
The JWST will continue to investigate WASP-39 b with other instruments in addition to observing other transiting exoplanets.
This will include smaller exoplanets as well as worlds that are much cooler than WASP-39 b. Astronomers hope that the JWST will be able to investigate the atmospheres of small rocky worlds just as it has for this gas giant.
Ultimately, this should give us an idea of how unique the planets of the solar system, including Earth, are.