Could another Earth exist?
It’s naive to think that our temperate rocky planet is unique in our vast universe—and in 1995, we found evidence the first evidence that the majority of other stars have orbiting planets too. Since then, we’ve detected thousands of “exoplanets” or “extra solar planets”, and currently have evidence for significant numbers of three types—gas giants, hot-super-Earths, and ice giants. In 2009, NASA’s Kepler Mission was launched specifically to search for terrestrial Earth-like planets, especially those orbiting within the “Goldilocks zone” of their stars where liquid water (and therefore life a we know it) might exist. The Kepler Mission seeks out exoplanets in the Milky Way by using the transit method: when a planet crosses in front of its star, i.e. “transits”, it causes the star’s brightness to dim by a tiny amount. Kepler continually and simultaneously monitors these transits, and since a planet’s transit will always last the same time and will always cause the same change in brightness, it’s a reliable method for confirming exoplanets. The planet’s orbital size can then be calculated, and so can its size and its temperature—which is key to determining habitability. Kepler has announced over 2,300 exoplanet candidates to date, and thanks to constantly improving technology, we’re discovering new exoplanets daily at an exponential rate.
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