Although Kepler 22-b, discovered earlier this year by NASA's planet-hunting telescope, is like a temperature twin to Earth, a new announcement today reveals two exoplanets that are Earth-like in size. Kepler-20e and Kepler-20f, NASA said, are the smallest planets found outside of our solar system orbiting a star.
“The primary goal of the Kepler mission is to find Earth-sized planets in the habitable zone," said Francois Fressin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., lead author of a new study published in the journal Nature. "This discovery demonstrates for the first time that Earth-size planets exist around other stars, and that we are able to detect them.”
Unfortunately, the two planets are far too close to the star for the temperature to be considered habitable. Kepler-20f reaches an estimated 900 degrees Fahrenheit and Kepler-20e rises to a whopping 1,400 degrees Fahrenheit. Due to their extreme temperature, the planets would not have water present.
According to a NASA press release, the planets are in a five planet solar system (Kepler-20) and orbit the star completely in a very short period of time. Kepler-20e completes an orbit around the star in 6.1 days and Kepler-20f makes its way around in 19.6 days.
The research notes an unusual arrangement in this solar system in terms of planet size:
In our solar system, small, rocky worlds orbit close to the sun and large, gaseous worlds orbit farther out. In comparison, the planets of Kepler-20 are organized in alternating size: large, small, large, small and large. In our solar system, small, rocky worlds orbit close to the sun and large, gaseous worlds orbit farther out. In comparison, the planets of Kepler-20 are organized in alternating size: large, small, large, small and large.
For this reason, scientists speculate that the system did not originate in its current location. The release states that the researchers think the planets could have formed far away from the star and then moved inward.
Here's Space.com's video report on the new findings: