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It has rain, water, clouds: so, maybe life too!

What a wonderful find — but does it have any point? Astronomers are thrilled by yesterday’s announcement about a habitable planet. The bad news: it would take two million years to get there. The extreme gravity would make walking impossible, and the sunlight is so fierce that, for a human, developing cancer would be inevitable. Yet planet K2-18b, which lies 110 light-years away in the constellation Leo, is the first world ever to be discovered which could realistically support alien life. Scientists have detected water vapour for the first time in the atmosphere of a planet beyond our solar system, where the temperature is in a survivable range. “Finding water in a potentially habitable world other than Earth is incredibly exciting,” said Angelos Tsiaras of University College London, where a team of astronomers made the discovery by analysing data from the Hubble Space Telescope. “This planet satisfies more requirements for habitability than any other we know about now.” The exoplanet orbits a red dwarf star. It is in what is known as the super-Earth category, with a mass eight times that of our home planet and twice its diameter. Life could, in theory, have evolved on K2-18b, given the existence of water and tolerable temperatures for biological molecules. The planet is closer to its star than Earth is to the Sun, orbiting once every 33 days. But the star is smaller and cooler than the Sun, giving it surface temperature similar to Earth. But any organisms there would not look like terrestrial life because they would have to tolerate the planet’s stronger gravity, and the likelihood of higher levels of radiation from its parent star than Earth receives from our Sun. The search for exoplanets around stars beyond the solar system began just 25 years ago. Since then, about 4,000 have been detected: a minute fraction of the 100 billion planets that our galaxy is thought to contain. The technology is only just reaching the point at which scientists can deduce something about characteristics of distant planets beyond their mere existence. But it will soon be hugely improved by scientific advances, including Hubble’s successor, the James Webb space telescope due to go operational in 2021, and the European Space Agency’s Ariel mission, a specialised planet-hunting observatory, scheduled for launch in 2028. Long shot This is all very interesting but of absolutely no relevance to us at all, according to one argument. Using current rocket technology, it would take two million years to get to K2-18b. It is pointless to dream about space colonies there. The most this discovery does is to keep lots of astronomers happy and fuel a few more sci-fi novels. “Entirely missing the point,” goes the opposing view. Can’t you see that if you find just one place where life could exist, then there will be others? Since the universe is so great and its size so vast — with hundreds of billions of stars in the Milky Way alone — then, unless the Earth is astonishingly special, the universe should be teeming with life. The only question is where are they all?. KeywordsLight-years - One light-year is the distance that light travels in one year, nearly 6 million million miles!

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