The Gas Giants (cont.)

Neptune

Neptune is even further out, 4.5 billion kilometers (2.8 billion miles) from the Sun. Through the telescope it is a green, featureless world, about the size of Uranus. Two moons have been detected. Neptune has remained untouched by the activity of the Space Age, although clouds have been detected in its atmosphere. The planet remains an enigma, too far away to see well from Earth, almost too far away to reach.

The clouds of far-off Neptune.
Neptune, the most distant gas giant planet from the Sun, is so far away that it is only a tiny, blurred image in Me 154-cm, (60-inch) telescope at the Catalina Observatory. The top three images show dark absorption bands, due to the presence of atmospheric methane (CH₄), across the planet's equator. The bright regions at the poles are produced by a high haze of ice crystals. The image at lower left shows the uniform, featureless appearance of the planet when seen in visible light. (Photographs courtesy of Catalina Observatory, Arizona.)