Sandra Szczsponik, age 9, of Coventry, Rhode Island, for her question:

How many moons has  Neptune?

Today we know that Neptune has at least thirteen moons. The one called Triton is bigger than our moon and it orbits around much faster. Our moon takes about 27 days to orbit around the earth, but Triton takes only siz; days to orbit around the planet Neptune. The second moon is much farther from Neptune and much smaller than Triton. It takes almost a whole earth year to make one orbit around the planet. This little faraway moon is named Oeried.

Neptune is 30 times farther from the sun than we are, so it is very cold and its days are not very bright. From this distance, our eyes cannot see the big planet or its smaller moons. But the telescope can. Telescopes spotted Neptune and Triton way back in 1846. They did not find little Nereid until about 100 years later.  Planetary spacecraft have provided new information on Neptune.  The following are recent statistics on the Planet Neptune.

Neptune Statistics

Planetary Symbol: Name in Roman/Greek Mythology: Neptune/Poseidon

Diameter: 49,493 km (30,760 miles) Rotation Period about Axis: 17.24 hrs

Mass: 102.4x10^24 kilograms (17.2 x Earth's) Revolution Period about the Sun: 165 years

Density: 1,638 kg/m^3 Tilt of Axis: 29o 36"

Minimum Distance from Sun: 4.46 billion km (2.77 billion miles)

Surface Gravity: 11 m/s^2 (1.12 x Earth's)

Maximum Distance from Sun: 4.54 billion km (2.82 billion miles)

Temperature at Cloud Tops: -210 degrees C ( -346o F)

Orbital Semi-major Axis: 30.07 AU (Earth=1 AU) Average Cloud Top Temperature (K): 63K

Minimum Distance from Earth: 4.3 billion km (2.68 billion miles)

Satellites/Rings: 13 known moons, faint rings