Tech UPTechnologyThe James Webb telescope detects CO2 on an exoplanet

The James Webb telescope detects CO2 on an exoplanet

The James Webb Space Telescope continues to amaze us with its results. Since the first telescope pictures were released in July , it has consistently lived up to expectations, bringing us science and discoveries every few weeks. This time it is about the discovery of carbon dioxide (CO 2 ) in the atmosphere of an exoplanet . This is not the first time it has been done, since in 2008 the Hubble Space Telescope made a similar discovery in the atmosphere of another exoplanet. However, James Webb’s discovery is nearly 10 times farther away than Hubble’s, as would be expected from its higher sensitivity.

This new telescope has been observing a star similar to the Sun , located about 700 light-years away in the constellation of Virgo. This star was named WASP-39 at the time of its discovery as it was the thirty-ninth star around which the WASP project observed an exoplanet. More recently it has been given the more pleasant name of Malmok. In 2011 the WASP project detected the planet WASP-39b , a gas giant of the type known as “hot Jupiter” , with a mass similar to that of Saturn (a quarter of the mass of Jupiter) but larger than Jupiter, with a radius 1.3 times larger. This large size and small mass means that the planet is very sparse , having a density about one-fifth the density of water.

The great size of WASP-39b is undoubtedly due to the temperature reached by its atmosphere, due to the proximity of the planet to the star . Temperatures of 900C have been measured from the exoplanet, which orbits its star every four days at one-eighth the distance that Mercury is from the Sun. This planet has been previously studied by telescopes such as Hubble or Spitzer, which detected water vapor, sodium and potassium in its atmosphere . The increased sensitivity of the James Webb telescope at infrared frequencies has now made it possible to detect carbon dioxide as well.

The planet WASP-39b , which was named Bocaprins three years ago, was detected using the transit method , whereby an exoplanet transits in front of its star (eclipses it) so that we can take advantage of the change in brightness received from Earth to detect it. This method , in addition to allowing us to detect distant exoplanets, allows us to study their atmosphere in some detail , since the light from their star is filtered by the gases that compose it, which will absorb certain frequencies but not others. This allows us, if we are sensitive enough, to study the chemical composition of these atmospheres in detail. With the combination of a thin atmosphere and frequent transits (every 4 days), the planet Bocaprins is a perfect candidate to study it with transmission spectroscopy , as this technique is known. That is why he has been chosen as one of James Webb’s first targets.

Using the Near Infrared Spectrograph (NIRSpec) on board the telescope, the team found that WASP-39b’s atmosphere absorbed more light than normal at wavelengths between 4.1 and 4.6 micrometres. , an unequivocal sign of the presence of carbon dioxide. James Webb’s sensitivity in this part of the spectrum will be key to the detection of water vapor, methane and carbon dioxide molecules in exoplanet atmospheres. This combination of gases may sound like something from another scientific discipline, as they are the three main gases responsible for global warming . This is so for precisely the same reason they are of particular interest to the James Webb telescope, for their absorption of infrared light .

The detection of such a clear signal of the presence of carbon dioxide in the atmosphere of the planet Bocaprins gives us hope about the ability of James Webb to detect this molecule in the atmosphere of smaller and more Earth-like planets . The composition of an exoplanet’s atmosphere can tell us a lot about its formation and subsequent evolution . It may also be key to discovering the first signs of extraterrestrial life. Carbon dioxide is one of the waste products created by life on Earth, although we also know of many geological and atmospheric processes that can create it. However, other compounds are produced almost exclusively by biological processes and detecting them in the atmosphere of an exoplanet would be an almost unequivocal sign of the presence of life on said planet.

These observations of the planet WASP-39b by the James Webb telescope have been accompanied by observations with other instruments of this and two other exoplanets. This has been part of the Early Release Science program, which has wanted to provide the scientific community with solid data in this area as soon as possible. This initiative aims to promote collaboration between institutions and the creation of free software tools that allow greater access to scientific knowledge .


Jamie Adkins, 2022, NASA’s Webb Detects Carbon Dioxide in Exoplanet Atmosphere, NASA

Ray Villard, 2008, Hubble Finds Carbon Dioxide on an Extrasolar Planet, NASA

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