Saturday science subject: The smallest exoplanet

Spanish astronomers have discovered the smallest planet outside of our solar system yet. As Reuters reports, the planet is a rocky one nicknamed GJ 436c, and it lies roughly 30 light years away in the constellation Leo. GJ 436c has a radius only 50% greater than the Earth's with a mass only five times greater. It circles its host star in around five days while rotating on itself only every 22 days—in other words, its days are more than four times as long as its years.

GJ 436c in its star system and compared with Earth. Source: CSIC.

Astronomers at the Consejo Superior de Investigaciones Científicas (CSIC) in Madrid, Spain found GJ 436c by studying distortions in the orbit of a larger planet that circles the same star. They believe the discovery is significant, because the same exoplanet detection technique could be used and refined to allow Earth-like planets to be discovered in only a few years. So far, all of the other exoplanets found have been either large gas giants or massive, rocky planets many times the size of the Earth.

According to Ignasi Ribas, who led the team that found the planet, astronomers are "just a few years away" from finding Earth-like planets and only about a decade away from discovering Earth-like planets that lie in the "Goldilocks Zone" of their host stars—not too close for liquid water to boil away, but not too far for it to freeze. Spanish speakers can learn more about GJ 436c by hitting the CSCI's website and checking out the official news release in PDF format.

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