Planet smallest known planet is PSR B1257+12A, one of the first extrasolar planets discovered, which was found in 1992 in orbit around a pulsar. Its mass is roughly half that of the planet Mercury. The smallest known planet orbiting a main-sequence star other than the Sun is Kepler-37b, with a mass (and radius) slightly higher than that of the Moon. Every planet began its existence in an entirely fluid state; in early formation, the denser, heavier materials sank to the centre, leaving the lighter materials near the surface. Each therefore has a differentiated interior consisting of a dense planetary core surrounded
The Empty Planet them a newspaper so they can quickly learn the human language. They reveal the strange image is a countdown. They demand the air and the sun, saying that if it is not given to them by the end of the countdown the human race will not return. Rani realises that they don't mean 'sun and air' but 'son and heir'. It turns out that Gavin's father was an alien king, who has now died. The robots have come to take Gavin to their planet and sent the news he is a prince in the energy trace, but Gavin never received