LONDON – Scientists for the first time have detected water vapor in the atmosphere of an exoplanet of a size comparable to Earth, making it “the best candidate” to be habitable found so far, according to a study published on Wednesday in Nature Astronomy magazine.
Planet K2-18b, with a mass eight times that of Earth and a diameter twice as large, was discovered in 2015 and could be a rocky body with a thick atmosphere or a frozen planet with a high concentration of water in its interior.
To date, the majority of exoplanets where scientists have been able to determine the contents of the atmosphere are gas giants, given the difficulties in determining the atmospheric composition of smaller bodies.
A team from London’s University College headed by Angelos Tsiaras analyzed K2-18b from data obtained by the Hubble Space Telescope.
Scientists used a technique known as transmission spectroscopy whereby they analyzed the light that filters through the exoplanet’s atmosphere when it passes in front of a star to detect traces of the chemical elements present there.
Using that technique, researchers found solid evidence of the presence of water vapor and also say that there could be a significant amount of hydrogen in the atmosphere.
At a press conference, Tsiaras said that this is the first exoplanet – that is, a planet outside our Solar System – that has the proper temperature to contain liquid water, an atmosphere and where water has actually been detected. All that makes it a prime candidate for being habitable.
Despite the fact that the precise composition of the gases has not yet been determined, the models prepared by the authors of the study indicate that up to half the atmosphere of K2-18b could be water vapor.
The exoplanet revolves around the red dwarf star K2-18 located some 110 light years from Earth in the constellation Leo.
Given the star’s high level of activity, scientists believe that the planet is exposed to much more radiation than Earth, thus potentially making the environment there more hostile to life.
Researchers hope that the next generation of space telescopes, including the James Web ‘scope, will be able to study small planets of this kind in more detail.
Over the next two decades, the team expects to find many new “super-Earths,” and thus this exoplanet could be the first of many such potentially habitable planets to be identified by scientists, said Ingo Waldmann, the coauthor of the study.