Astronomers Discovered Three Alien Planets Smaller Than Earth

Astronomers have discovered the three smallest alien planets. The alien worlds, detected using publicly available data from NASA’s Kepler mission, are 0.78, 0.73 and 0.57 times the diameter of Earth, and the smallest one is roughly Mars-size. The three exoplanets orbit a red dwarf star known as KOI-961, which is just one-sixth the size of our sun and is located 120 light-years away, in the Constellation Cygnus (The Swan). The three planets orbit very close to their star, just 0.6 to 1.5 percent the distance from Earth to the sun. It takes each of them less than two days to zip around KOI-961. All three exoplanets are thought to be rocky like Earth. However, their closeness to their star makes them too hot to be in the habitable zone, the area around  a star neither too hot nor too cold for liquid water to exist on the surface. The surface temperatures of these planets range from 720 Kelvin (836 degrees F) to 450 Kelvin (350 degrees). Kepler finds planets using a technique known as the transit method. It watches for tiny dips in a star’s brightness caused when a planet crosses the face of, or transits, the star, blocking some of its light. To date, Kepler has found about 35 alien planets, but it’s flagged an additional 2,300 exoplanet candidates that await confirmation by follow-up studies. Kepler scientists have estimated that at least 80 percent of these potential planets will end up being the real deal.