The Great Dark Spot Is in the center of the disk in this 1989 Voyager 2 image. The short-lived storm was gone when the Hubble Space Telescope looked for it in the mid-1990s.

rings and moons

Thirteen moons are known to orbit Neptune, and more small ones probably exist. Just one of the moons, Triton, is large and round. The innermost four lie within the ring system. This consists of five complete rings, the outer of which contains three dense regions of material, as well as a sixth partial ring. The rings are sparse and made of tiny pieces of unknown composition. Voyager 2 revealed the rings, but earlier observations made from Earth had predicted their existence.

the rings of neptune

Four rings are visible in this Voyager 2 view. A diffuse band of material, named Lassell, lies between the two bright rings, Adams and Le Verrier. Closest to Neptune is the Galle ring.


The icy moon Triton was discovered just 17 days after Neptune. It is bigger than Pluto. Dark surface patches are the sites of geyserlike eruptions.

observing neptune

Neptune is far too distant to be seen by the naked eye alone. At its brightest, it reaches magnitude 7.8 and can then be seen through binoculars or a small telescope. Even then the planet will resemble a faint star. a telescope larger than about 6 in (150 mm) aperture will resolve the planet into a disk shape. However, only the most powerful instruments will reveal any detail, such as changes in surface brightness.

view through a telescope

Neptune's disk is seen twice here, next to Triton. Images taken on separate nights are combined to show their movement against the fixed stars.


Pluto is a dark, desolate world of rock and ice. Difficult to observe from Earth, it has not yet been visited by a space probe and remains largely unknown. In 2006, it was classified as a dwarf planet—a body much like a planet but that has not cleared the region around its orbit.

structure and atmosphere

At the heart of tiny Pluto is a large rock core, surrounded by a mantle and crust of water ice. The ice is not pure water but includes ices of nitrogen, carbon monoxide, and methane. A nitrogen atmosphere surrounds Pluto. Surface ice evaporates and replenishes the atmosphere when its orbit takes it close to the Sun. In size, structure, composition, and orbit, this dwarf planet is very different from its planetary neighbors.

mantle rich in water ice mantle rich in water ice large rocky, core

thin, icy crust,


Pluto is thought to be 70 percent rock and 30 percent water ice. The rock has sunk to is center, and is surrounded by an ice mantle, topped by ice.

large rocky, core thin, icy crust, nitrogen (99.97%)/


Pluto's atmosphere is almost entirely nitrogen and is temporary because Pluto's gravitational pull cannot hold on to the gas.

0 0

Post a comment