Uranus (YOOR uh nuhs) was the first planet discovered through a telescope, but when he discovered it in 1781, astronomer William Herschel initially believed it was a comet. The seventh planet from the sun, Uranus appears to be tipped on its side! One pole - and then the other - faces the Sun on the planet's long orbit.
Uranus, Neptune, Jupiter and Saturn are the gas giants. In the outer reaches of the Solar System, the dust in the solar nebula that formed the planets was rich in rocky materials and in ices of methane, ammonia, and water.
Uranus probably formed more slowly than Jupiter and Saturn, and it could not capture large amounts of helium and hydrogen from the nebula with its gravitational pull. It is likely that Uranus also was knocked over by another large object when it was forming causing it to be tipped by about 90 degrees compared to the other planets. (Image Right: Uranus, Courtesy of NASA)
