The first time discovered water in the atmosphere of a planet orbiting within the habitable zone of a distant star. The finding makes the world is called K2-18b – a plausible candidate in the search for alien life. The new space telescopes might be able to determine whether K2-18b’s atmosphere contains gases that could be produced by living organisms.
The details were published in the scientific journal Nature Astronomy. The lead scientist, Prof Giovanna Tinetti of University College London (UCL), described the discovery as mind-blowing. This is the first time that we have detected water on a planet in the habitable zone around a star where the temperature is potentially compatible with the presence of life.
The habitable zone is the region around a star where temperatures are considered sufficiently benign for water to exist in liquid form on the surface of a planet. The new planet is just over twice the size of Earth – in a planet category known as a super-Earth and has a temperature cool enough to have liquid water, between zero and 40C.
K2-18b is 111 light-years – about 650 million miles – from Earth, too far to send a probe. So the only option is to wait for the next generation of space telescopes to be launched in the 2020s and to look for gases in the planet’s atmosphere that could only be produced by living organisms. The first exoplanet was discovered in 1992, orbiting a pulsar (a neutron star that emits electromagnetic radiation)
The researchers determined some of the chemicals in their atmosphere by studying the changes to the starlight as the planets orbited their suns. The light filtered through the planets’ atmospheres was subtly altered by the composition of the atmosphere.
K2-18b cannot be classified as a mini-Neptune, it is more likely to be a planet with an interior of rock and ices. These types of planets are sometimes called ‘ocean planets’.