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The planets beyond Saturn are far away from Earth, and astronomers need large telescopes to see them.
Uranus was discovered in 1781, and Neptune in 1846. Pluto was not discovered until 1930. All three planets are cold because they are far from the Sun. Uranus is twice as far from the Sun as Saturn, or about 2 billion miles. Neptune is 2.8 billion miles from the Sun, and Pluto is 3.5 billion miles from the Sun.
Uranus and Neptune are giant balls of water surrounded by thick atmospheres of hydrogen. Another gas, called methane, absorbs atmospheric red light from the Sun but reflects blue and green light back into space. Methane makes both Uranus and Neptune appear blue-green in color. On Earth, methane can be produced by bacteria. Families of moons and dark rings of dust orbit both planets.
