Two planets have been discovered, about 1,000 light years away from Earth.
Both of the planets are about the size of Earth. Kepler-20e is slightly smaller, and Kepler-20f is slightly larger than Earth.
The surface of the planets are too hot for water to exist on them; it would not be possible for life to exist on them either. They are hot because they orbit close to a star very much like our sun.
Kepler-20e has a termperature of about 760 degrees Celcius. (In contrast, Earth’s average surface temperature is 14 degrees Celsius.)
The planets were discovered during a mission by NASA using the Kepler space telescope. They have been combing the skies searching for planets since about 2009; the mission will last about 3.5 years. One of the most important goals of the mission was to find Earth-sized planets. These two are the first ones they have found.
The planets are part of a five-planet solar system.
The discovery demonstrates for the first time that Earth-sized planets exist around other stars, said a spokesperson for the mission. (They are known as “extrasolar” planets.)
The scientists used an interesting method of discovering the planets. They monitor a section of the sky with the Kepler telescope and watch the brightness of about 145,000 stars. When the brightness of a star changes, it may indicate the presence of a planet passing by it. When it happens a few times, they become more certain it is caused by a planet.