With the James Webb space telescope, researchers are able to take the most precise look at an exoplanet to date. The composition of the atmosphere is determined in more detail than ever before. The success gives hope that one day extraterrestrial life will be discovered.
Until the early 1990s, it was not certain whether there were any planets outside the solar system. Thousands are now known. And thanks to the new James Webb Space Telescope (JWST), researchers are now discovering more details about the exoplanet WASP-39b than ever before. The telescope reveals a wealth of information about the planet’s atmosphere, which even allows conclusions to be drawn about its formation. The results were published in several articles in the journal “Nature”.
“Data like this is a game changer,” says Natalia Batalha of the University of California at Santa Cruz, who coordinated the observing program, according to a statement from the Max Planck Institute for Astronomy (MPIA), which was involved in the research. The research team’s new results are also a kind of test run for the methods that astronomers hope to use to detect life on distant planets in the future.
The now observed planet WASP-39b is similar in mass to Saturn in our solar system, albeit with a slightly more bloated atmosphere. It orbits a star that is only slightly less massive than the Sun. The entire system is about 700 light-years from Earth.
What the researchers discovered: They succeeded in examining the chemical composition of the atmosphere in more detail than ever before. This resulted in a detailed listing of certain molecules that are present in it. Just last August, the team published detection of carbon dioxide in the atmosphere of WASP-39b, the first definite evidence of this molecule on an exoplanet.
A hitherto puzzling feature in the atmosphere of WASP-39b has now been determined to be sulfur dioxide – again the first detection of this type on an exoplanet. Photochemistry of exoplanets was also observed for the first time: Sulfur dioxide molecules are formed when high-energy photons from the star hit the outer layer of the atmosphere – just like ozone is formed in the earth’s atmosphere.
Some of the new data even allow conclusions about the formation of the exoplanet. According to the authors, the ratios of carbon to oxygen, potassium to oxygen and sulfur to hydrogen point to a history of formation in which smaller planetary precursors collided and ultimately came together to form today’s large planet. According to the researchers, the fact that oxygen is much more common in the atmosphere than carbon indicates that WASP-39b was formed much further away from its star and only later moved to its current, much smaller orbit.
The comparison of observations and models also provides information about the planet’s clouds: It is not a question of a closed cloud cover, but of a looser accumulation of clouds. However, at the high temperatures prevailing on WASP-39b, these do not consist of water, but of substances such as sulfides and silicates, which occur as rock on Earth.
The observations raise expectations for many more discoveries to come. “These early observations are a foretaste of all the amazing scientific results to come from the JWST,” says MPIA director Laura Kreidberg. “We put the telescope through its paces and tested its performance in detail. The observations were almost error-free, even better than we had hoped.”
So-called transits are crucial for such observations of exoplanets, i.e. when a planet orbiting a distant star passes exactly between the star and the earth from the point of view of observers on earth. Exoplanets are usually too far away to be seen in detail. However, the star’s light shines through the planet’s atmosphere, causing the elements within to leave traces in the light spectrum. By means of so-called spectroscopy, the “colors” of the elements become visible to telescopes during a transit.
The current observations are also important for one of the greatest future goals of telescopic astronomy: detecting traces of life on exoplanets. According to current plans, the discovery of life on an exoplanet should be very similar in principle to that of WASP-39b: a future space telescope could detect telltale combinations of elements in the atmosphere during an exoplanet transit – such as an excess of atmospheric oxygen, which could indicate the presence of certain types of living beings on this planet.
Researchers therefore see the latest observations of WASP-39b as a test run for the observation techniques that would be used in the search for life in space. In addition, these also allow for a more complete understanding of exoplanet atmospheres – important for distinguishing between the chemistry of exoplanets with and without the participation of living organisms in the search for life.
