Know the Exoplanets where aliens can exist

New Delhi: An exoplanet is a planet outside the Solar System. For centuries philosophers and scientists supposed that extrasolar planets existed, but there was no way of detecting them. The first confirmed detection of exoplanet came in 1992, with the discovery of several terrestrial-mass planets orbiting the pulsar PSR B1257ი.Now till date more than a thousand such planets have been discovered. Recent discoveries have revealed Earth-sized and smaller planets and a few that exhibit other Earth-like properties. The discovery of these planets has intensified interest in the search for extraterrestrial life.Thus working on the same research project in 2012 the Habitable Exoplanets Catalog owned by the University of Puerto Rico at Arecibo lists nine planets that have the best chance for life beyond our solar system.Here are the nine planets which are expected to host alien life:1. Gliese 581g It was discovered in 2010, but there has been difficulty in getting it confirmed. It orbits its parent star, Gliese 581, about every 30 days in the constellation Libra.According to researchers it could sustain liquid water on its surface and could potentially host life similar to that on Earth.It is the top candidate for alien life. It is about 20 light-years away from Earth's sun, and is two to three times as massive as Earth. 2. Gliese 667Cc The system lies at a distance of about 6.8 pc from Earth.The planet is at least 4.5 times bigger than Earth, and takes 28 days to make an orbit around its parent star. GJ 667C is actually part of a triple-star system. The star is an M-class dwarf star that is about a third of the mass of Earth's sun.3. Kepler-22b While Kepler-22b is bigger than Earth, it circles a star that is quite close in size and temperature to Earth's sun. Kepler-22b is 2.4 times Earth's size and, assuming its greenhouse effect is similar to Earth's, has an estimated surface temperature of 72 degrees Fahrenheit (22 degrees Celsius.) Its star system is about 600 light-years away from Earth's sun, in the constellation Cygnus.4. HD 40307g “Super-Earth” HD 40307g orbits comfortably inside the habitable zone of its parent star. It lies about 42 light-years away from Earth in the constellation Pictor. It is so close by that future telescopes may be able to peer at its surface. It orbits its parent star about 56 million miles (90 million kilometers) away, which is just over half of the Earth-sun distance of 93 million miles (150 million kilometers.)5. Tau Ceti f Tau Ceti f is a super-Earth candidate like its sibling Tau Ceti e, but it orbits close to the outer edge of Tau Ceti's habitable zone. Tau Ceti f is at least 6.6 times as massive as Earth and could be suitable for life, if its atmosphere traps significant amounts of heat.6. Gliese 581d At least one study supposes that Gliese 581d might have a thick, carbon dioxide atmosphere. It is about seven times more massive than Earth, orbits a red dwarf star, and is a sister planet to the also-potentially-habitable Gliese 581g. At just 20 light-years away from the sun, Gliese 581d is essentially in Earth's backyard.7. Gliese 163c The mass of Gliese 163c puts the planet in a gray zone. The planet is seven times the mass of Earth, which could make it a very large rocky planet or a dwarf gas giant. Gliese 163c whirls around its dim planet star every 26 days, at a distance of 50 light-years away from Earth. Its parent star is in the constellation Dorado.8. Tau Ceti e The planet candidate Tau Ceti e, which was detected in December 2012, is found just 11.9 light-years from Earth. This world is a “super-Earth” at least 4.3 times as massive as Earth. Depending on its atmosphere, Tau Ceti e could be a mildly hot planet suitable for simple life, or a scorching world like Venus.9. HD 85512b HD 85512b was announced in 2011 as part of a treasure trove of 50 planets discovered by the High Accuracy Radial velocity Planet Searcher instrument, or HARPS, in Chile. This planet is about 3.6 times more massive than Earth. It lives about 35 light-years away from Earth's sun, in the constellation Vela (the Sail). Researchers are hoping to one day figure out if there is water on its surface