New discoveries of many super-Earth planets orbiting very close to sun-like stars have started to make Earth's solar system look a little lonely. The mystery of why Earth ended up without any super-Earth cousins continues to puzzle astronomers as they try to better understand the unusual history of the Solar System and the evolution of planets in general.
The uniqueness of our solar system first became clear when astronomers began discovering hundreds of extrasolar planets orbiting other stars. They recently found that around 30 to 50 percent of stars similar to the Sun have hot super-Earths-planets orbiting very close to their parent stars with up to 10 times as much mass as Earth.
We just haven't found any yet. To read more, click here.