K2-18b also known as EPIC 201912552 b is a distant exoplanet around a small red dwarf star (K2-1) over 110 light-years away in the constellation Leo. It was identified as one of over 1,200 exoplanets discovered during the Kepler space telescope program “Second Light” K2 mission in 2015. The planet was detected through variations in the star’s light curve caused by the transit of the planet in front of the star as seen from Earth. The planet was designated “K2-18b” as it was the eighteenth planet discovered during the K2 mission. Based on the high level of activity of its red dwarf star, K2-18b may be more hostile to life, since the planet is likely to be exposed to high-energy radiation.
Though very little is known about the interior of this planet, NASA scientist indicate that its mass is about eight times that of earth, its size and surface gravity are much larger than Earth’s, and its radiation environment may be hostile. The planet has attracted the interest of scientists all over the world, since for the first time, researchers have detected water vapour signatures in the atmosphere of a planet beyond our solar system that resides within the “habitable zone,” the region around a star in which liquid water could potentially pool on the surface of a rocky planet. If confirmed by further studies, this will be the only exoplanet known to have both water in its atmosphere and temperatures that could sustain liquid water on a rocky surface. Liquid water would only be possible if the planet turns out to be terrestrial in nature.
A team of UCL researchers have used open-source algorithms to process archive data captured by the NASA/ESA Hubble Space Telescope between 2016 and 2017 with the aim of analyzing the starlight filtered through the atmosphere of the K2-18b exoplanet. Their results published in a recent Nature Astronomy article revealed the molecular signature of water vapour as well as the presence of hydrogen and helium in the planet’s atmosphere.
The authors believe that other molecules, including nitrogen and methane, may be present but they remain undetectable with current observations. Further studies are required to estimate cloud coverage and the percentage of atmospheric water present.
Though these results sound interesting, scientists warn that except for a miracle, several decades of studies are required to properly characterize K2-18b, to be able to tell is if is habitable or not for earths life forms and even if it were, the distance of the planet from earth will take several hundreds of generations to get to it with the present level of space vehicle technology.
September 23, 2019