Mercury

Mercury is the closest to the sun. Mercury formed about 4.5 billion years ago when gravity pulled swirling gas and dust together to form this small planet nearest the Sun. Like its fellow terrestrial planets, Mercury has a central core, a rocky mantle and a solid crust.Timocharis made the first recorded observation of Mercury in 265 BC. Other early astronomers that studied Mercury include Zupus (1639), who studied the planet's orbit. Mercury is one of the five classical planets visible with the naked eye and is named after the swift-footed Roman messenger god. It is not known exactly when the planet was first discovered - although it was first observed through telescopes in the seventeenth century by astronomers Galileo Galilei and Thomas Harriot.