 Skywatchers have discovered 45 mystery worlds orbiting the Sun on the edge of the solar system.The new finds lie beyond the eighth planet from the Sun, Neptune, which lies 2.5 billion miles away. They are made up of a mixture of rock and ice like the most distant planet, Pluto. The record haul of objects, ranging from 30 to 300 miles wide, was made in an intensive search by US astronomers at the Southwest Research Institute at Boulder, Colorado. They are part of a belt of icy remnants left over from the formation of the solar system. One new world announced last year ten billion miles from the Sun has been found to be larger than Pluto. The object, nicknamed Xena, is 1,490 miles wide (2,384km), observations with the Hubble space telescope revealed. Pluto is 1,422 miles across (2,275km) – smaller than the Moon – and around 4billion miles from the Sun. The result will reopen the debate about whether Pluto should really be considered a planet. |