One of the other planets, Kepler 442b, lies in the same constellation 1,100 light years away. It is about a third larger than Earth, receives about two thirds as much starlight, and has a 60% chance of being rocky, according to a report to be published in
The Astrophysical Journal.
Guillermo Torres, lead author on the study, said the size and amount of light falling on the planets made them the most Earth-like planets yet found beyond our solar system. Before their discovery, the exoplanets most similar to our own were Kepler 186f, which is 10% larger than Earth and receives a third as much light, and Kepler 62f, which is 40% larger and gets about 41% as much light.
The scientists do not know if the planets have atmospheres, but if they are cloaked in insulating layers of gas, the mean temperatures of Kepler 438b and 442b are expected to be about 60 and zero degrees Celsius respectively.
The Harvard-Smithsonian team used a computer program called Blender to confirm that the planets originally spotted by the Kepler space telescope were real. False sightings can happen when pairs of stars that lie behind the one being studied eclipse each other, causing the background light to dim slightly. In some cases, this can be mistaken for a planet moving in front of its star.
“The pair of stars can be way behind the target star, but if they are in the same line of sight, the result is a very tiny dimming that can look like a planet,” said Torres.