A Planet is a rocky body or a gaseous body orbiting a sun or star. In the Solar System there are 8 planets. Pluto is now considered a dwarf planet. Exoplanets or Extra Solar Planets are planets orbiting other stars. In 2010 over 500 exoplanets were known.  and more are continually discovered, just under 800 were known in mid 2012. A high proportion of stars have planets. Large gaseous planets are more easily discovered than smaller rocky planets which can possibly support life. Scientists currently do not know how rare or common life is in the universe. There is one planet where without doubt life exists. The one planet known to have life.