Three recently discovered exoplanets are the most Earth-like objects known to humans so far. An exoplanet is a planet outside our solar system that orbits some star other than the Sun. Two of the planets discovered orbit a star called Kepler 62, which is about 1,200 light years away from us. Kepler 62 is smaller and cooler than our sun and has 5 planets orbiting it. The two outer planets, Kepler 62-e and Kepler 62-f, are believed to be Earth-like planets. A sun-like star even further away (about 2,700 light years from us) called Kepler 69 has two planets orbiting it. The outer planet called Kepler 69-c is a candidate for being Earth’s twin.
These three planets are considered to be in the “habitable zone”, also called the “goldilocks zone”. Umm, what does that mean? Remember the story of Goldilocks and the Three Bears? Goldilocks doesn’t like the soup that is too hot or too cold, she likes the one that has just the right temperature. She doesn’t like the bowl that is too big or too small, she likes the one that is just the right size. If a planet is in the “goldilocks zone”, it implies that it has just the right size, temperature, and distance from its star to be able to support life on it. Most scientists believe water is needed to have life on a planet, and therefore, they look for planets which could contain liquid water.
Kepler 69-c is about 70 percent larger than Earth, and takes about 242 days to orbit its star. Kepler 62-e is about 60 percent larger than Earth, and takes 122 days to orbit its star. Kepler 62-f is about 40 percent larger than Earth. It takes 267 days to orbit its star, and is likely to be a rocky planet. As the names indicate, these three exoplanets were discovered by Kepler, an American spacecraft with a very powerful telescope.
Before these discoveries, the most Earth-like planet discovered was called Kepler-22b. This planet is about 2.4 times the size of Earth and is located 600 light-years away. A light year is the distance that light travels in a year (about 6 trillion miles or 10 trillion km).
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The first exoplanet was discovered in 1992, and so far, over 850 exoplanets have been confirmed.
Image Credits: NASA Ames/JPL-Caltech for Kepler 62 and Kepler 69 images