Researchers have announced the discovery of the first-known Earth-sized exoplanet.

"Researchers say this discovery is unique because the planet, called Kepler-186f resides in a temperate region around its host star where water could exist and could possibly sustain life," a National Science Foundation news release reported.

Earth-sized planets are hard to spot in the first place because of the way they contrast with their host stars. The Kepler telescope was the first to spot Kepler-186f and the W.M. Keck and Gemini observatories worked hard to confirm the planet's existence.

Its host star Kepler-186 is an m1-type dwarf star. It exists inside of the Milky Way and is relatively close to our own stellar neighborhood.

The star is believed to be orbited by five small-sized planets, four of which orbit to closely to the star so any liquid water would immediately evaporate.

The researchers used the Gemini north telescope to take a closer look at this intriguing star system. The details of the system were enhanced by a "visiting differential speckle survey instrument," the news release reported.

"Researchers say the observations from Keck and Gemini on Mauna Kea in Hawaii, combined with other data, calculations and analysis, allowed the team to be 99.8 percent confident that Kepler-186f is real," the news release reported.

"This is an historic discovery of the first Earth-size planet found in the habitable zone around its star," UC Berkeley astronomer Geoffrey Marcy wrote in an email to the Los Angeles Times. "This is the best case for a habitable planet yet found. The results are absolutely rock solid."

The SETI Institute works to find life on other planets. Knowing habitable planets are so close to home could help us reach them with radio waves in the near future, the Los Angeles Times reported.
"Whether we are an extremely rare fluke - a phenomenon that only happens once in a universe - or in a galaxy teeming with life is a very basic question not only of science, but of our existence," Dimitar Sasselov, a planetary astrophysicist at the Harvard-Smithsonian Center for Astrophysics who was not involved in the study told the Los Angeles Times. "[It's] the first time in human history we have a good shot at answering that question, and that's very exciting."

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