| Planet | Description (All quoted values are approximate) |
| Kepler-22 b | Discovered by the Kepler space telescope, and announced in December 2011, this planet is about 2.4 times the diameter of the Earth, but its mass and composition are not known. Assuming a density similar to that of the Earth, which is about 5.5 times the density of water, then it would weigh nearly 14 times as much as the Earth with a surface gravity 2.4 times that found here on Earth. If, however, the density was only about 40% that of the Earth's, it would have a surface gravity very close to that of the Earth. This is all highly conjectural as it could also be an ice-giant like Neptune, albeit somewhat smaller. It orbits its star at a distance of about 0.85 AU (127 million km) once every 289.9 days. The eccentricity of the orbit is unknown, but assuming it is roughly circular and that the greenhouse effect is similar to that of the Earth, the average surface temperature would be around 295K (22ºC or 72ºF) compared to Earth's average of 288K (15ºC or 59ºF). Alternatively, if the greenhouse effect is more like that on Venus, the average surface temperature would be closer to 740K; so not too hospitable! |
Extra Solar Planets
Kepler-22 is a G-type star that lies about 590 light-years away from Earth. It is somewhat smaller (about 98% of the radius) and lighter (about 97% of the mass) than the Sun, and gives off about 25% less energy. It is important in that it has an Earth-like planet that orbits within its habitable zone. Note that claims in the popular press about it being another Earth with seas and moderate temperatures are total fantasy on their part. The makeup of the planet and its surface conditions are unknown as of today; January 2015.