More than a year and a half after its launch on December 25, 2021, NASA’s James Webb space telescope has made numerous discoveries. This week, the US agency and ESA, the European space agency, announced that Webb detected carbon-containing molecules such as methane and carbon dioxide around the planet K2-18b. Tentative evidence of a sign of life on a distant planet.
Cautiously, the researchers stressed, however, that the detection on the planet located 120 light years away is “not robust”, and that more data is needed to confirm its presence.
Facts
The exoplanet K2-18b is located approximately 124 light years from Earth, in the constellation Leo. It orbits a red dwarf, a star smaller and cooler than the Sun, and has at least one companion, K2-18c, of 8.6 Earth masses, explains the magazine Science and Future. It has aroused the interest of astronomers around the world in recent years and the discovery of water vapor by the Hubble space telescope. More recently, at the end of summer 2023, the James Webb telescope was able to analyze the light from the star K2-18 as it passed through the atmosphere of K2-18b and thus draw up its spectroscopic profile, in order to be able to determine its chemical composition.
The results, which should appear in the journal The Astrophysical Journal Letters, indicate the presence of methane and carbon dioxide at 1% in the atmosphere, consisting mainly of hydrogen. According to the researchers, the presence of the two molecules reinforces the hypothesis that this planet could host an ocean of liquid water.
The context
For the past year, James Webb has continued to dazzle astronomers with images of unprecedented precision. He observed the most distant galaxies ever detected and supermassive black holes, measured for the first time the temperature of rocky planets “cousins” of the Earth, and even began to analyze the atmosphere.
“In just one year, the James Webb telescope has transformed humanity’s view of the cosmos,” NASA boss Bill Nelson said in a statement. “Each new image is a discovery, which encourages scientists across the world. world to ask and answer questions they couldn’t even dream of before.”
One of the telescope’s main missions is the exploration of the very young universe, only a few hundred million years after the Big Bang. Another major area of research: the study of exoplanets, that is to say planets outside the solar system. It should also help to better understand the formation and life cycle of stars.
Why it matters
“It’s the first time that [des molécules contenant du carbone] are both discovered in the atmosphere of a small planet located in the habitable zone”, rejoiced in the columns of Parisian Subhajit Sarkar, of Cardiff University (Wales), one of the co-authors of the study to appear in The Astrophysical Journal Letters.
This detection confirms the immense contribution of the James Webb telescope to analyzing the composition of exoplanets. It is the successor to the Hubble space telescope, itself still in operation. Unlike Hubble, which observes the Universe mainly in the visible spectrum, James Webb works in the infrared. This allows it to detect much weaker glow, and therefore to see much further. “Being able to observe molecules on a temperate planet is a leap forward that James Webb offers,” enthuses the Parisian Benjamin Charnay, CNRS astrophysicist at the Paris Observatory.