Neptune
Neptune is the
second to the last of the planets. In some cases Neptune is the
farthest of the planets from the sun. Neptune and pluto cross orbits
twice in a rotation around the sun. One of these switches puts
Neptune farther and one puts Neptune closer then Pluto. Most of the
time Neptune is closer but during that 1 month (Earth time) Neptune
is the farthest planet out.
Neptune is the outermost planet of the gas giants. It has an
equatorial diameter of 49,500 kilometers (30,760 miles). If Neptune
were hollow, it could contain nearly 60 Earths. Neptune orbits the Sun
every 165 years. It has eight moons, six of which were found by
Voyager. A day on Neptune is 16 hours and 6.7 minutes. Neptune was
discovered on September 23, 1846 by Johann Gottfried Galle, of the
Berlin Observatory, and Louis d'Arrest, an astronomy student, through
mathematical predictions made by Urbain Jean Joseph Le Verrier.
Neptune is a dynamic planet with several large, dark spots reminiscent
of Jupiter's hurricane-like storms. The largest spot, known as the
Great Dark Spot, is about the size of the earth and is similar to the
Great Red Spot on Jupiter. Voyager revealed a small, irregularly
shaped, eastward-moving cloud scooting around Neptune every 16 hours
or so. This scooter as it has been dubbed could be a plume rising
above a deeper cloud deck.
Sun
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
Neptune Statistics
Discovered by Johann Gotfried Galle
Date of discovery September 23, 1846
Mass (kg) 1.024e+26
Mass (Earth = 1) 1.7135e+01
Equatorial radius (km) 24,746
Equatorial radius (Earth = 1) 3.8799e+00
Mean density (gm/cm^3) 1.64
Mean distance from the Sun (km) 4,504,300,000
Mean distance from the Sun (Earth = 1) 30.0611
Rotational period (hours) 16.11
Orbital period (years) 164.79
Mean orbital velocity (km/sec) 5.45
Orbital eccentricity 0.0097
Tilt of axis (degrees) 28.31
Orbital inclination (degrees) 1.774
Equatorial surface gravity (m/sec^2) 11.0
Equatorial escape velocity (km/sec) 23.50
Visual geometric albedo 0.41
Magnitude (Vo) 7.84
Mean cloud temperature -193 to -153°C
Atmospheric pressure (bars) 1-3
Atmospheric composition
85%
13%
2%