Uranus is the seventh planet from the Sun. It was discovered in 1781 by William Herschel and was the first planet discovered with a telescope. Uranus has the third largest planetary radius and fourth largest mass. It is composed primarily of ice giants like Neptune with hydrogen, helium, water, ammonia and methane in its atmosphere, which is the coldest in the solar system. Uranus has a unique configuration where its axis of rotation is nearly sideways compared to its orbit, so its poles lie along its equator.