Neptune The Blue Planet

In This Slide Show… The discovery of Neptune What a day on Neptune would be like Neptune compared to earth Facts about Neptune’s moons         

A New Planet Scientists in the early 1800 discovered that the planet Uranus was not following the orbit they had planned for it. They guessed that something was pulling on it even farther out in space. By 1846 astronomers had calculated it’s route and a few months later, an observer in Germany saw an unknown object in the sky. It was the new planet, Neptune. Since then, the information we have gotten about Neptune has come from observation and from Voyager 2 as it flew by.

Neptune

Composition You could put 60 Earths into Neptune and still have some room. Neptune is mostly made of Hydrogen, Helium and Methane gas.

Interesting Facts • Neptune actually has ONLY orbited the sun once since we discovered it in 1846! It takes 165 years for it to orbit the sun. • Triton is moving in the opposite direction that Neptune is moving and is steadily moving closer to Neptune. When it collides with Neptune it will create a ring system that will rival and may exceed Saturn’s. • Neptune’s Temperature is about –235 degrees F. • The Great Dark Spot at Neptune’s equator is not there anymore, but in 1997, Hubble Space Telescope saw another similar storm in Neptune’s Northern Hemisphere. • The winds on Neptune are extremely fast, traveling 3 times faster than Jupiter’s winds, and 9 times faster than Earth’s.

Statistics Neptune has an average distance from the sun of about 4,497,000,000 kilometers. Neptune is about 49,500 kilometers across. Neptune rotates once in about 16 hours.

Neptune’s Moons Neptune has 14 known moons. The largest moon, Triton, is the coldest known place in the solar system, with an average temperature of –235 degrees Celsius. The other moons are Naiad, Thalassa, Despina, Galatea, Larissa, Proteus and Nereid.

Sir Isaac Newton’s laws of planetary motion and his Universal Law of Gravity allow astronomers to calculate the position of celestial objects (and spacecraft and satellites!) at any time in space. This is referred to as Newtonian Celestial Mechanics. F = G x m1 x m2 r2 (Universal Law of Gravity), where F = gravitational force; G = universal constant of gravitation; m1 and m2 = the masses of two bodies; and r = the distance between them. “Two bodies attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them”.

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Lick Observatory image of Neptune and two of its moons

January 23, 1989, images of Neptune, 2 hours apart, taken by the approaching Viking spacecraft. Moving across the planet at ~30° S latitude is a bright cloud feature.

High-altitude cirrus-like clouds in Neptune’s atmosphere 50 – 150 km wide and maybe 50 km above main clouds

Hubble and Keck views of Neptune, showing storms with Equatorial winds of 1,400 km/hour

Neptune’s Great Dark Spot (“Scooter”) moving east around planet, driven by strong, 700 miles/hour west winds

Relative cloud motion in Neptune’s atmosphere

Neptune’s Dark Spot (“Scooter”) and smaller Dark Spot 2 moving eastward around the planet at different speeds

Neptune’s Great Dark Spot (“Scooter”) and white cirrus-like clouds

Magnetic field of Neptune. For comparison, the magnetic field of earth is ~ 0.35 Gauss

The 2 most prominent, clumpy rings of Neptune (clumping of material) discovered by Voyager. Neptune is overexposed to show rings.

New moon of Neptune, 1989N1, discovered by Voyager New moon of Neptune, 1989N1, discovered by Voyager. The large crater is 400 km in diameter.

Crescent of Neptune with its moon Triton in the background

Neptune’s moon Triton is 2,705 km in diameter Neptune’s moon Triton is 2,705 km in diameter. Bright ice cap in southern hemisphere (top) (notice black streaks), and dark terrain with “highways” below.

Dark, active nitrogen geysers on Triton; constant direction of streaks hints at a very thin atmosphere

“Cantelope terrain” on Triton hints at tectonic processes

Possible frozen lakes (of water, ammonia and salts?) on Triton

Neptune’s moon Triton Imaged by Voyager 2 in 1989 Triton moves around Neptune opposite to the planet’s rotation and movement around the Sun, but synchronous, i.e., the same side of Triton always faces Neptune The diameter of Triton is 2,705 km, 3/4 the size of our Moon It was probably captured, just like Pluto Its surface is made of solid methane (CH4) and N2, with T = - 400° F Its pinkish color is due to organic compounds that formed from CH4 and N2 There are no large impact craters; hence, the surface is young (constantly being resurfaced) The albedo is very high, 0.80 and, hence, the moon is bright (presence of ices) S pole region has N2 fumaroles; ejecta are wind-blown, thus, there is a tenuous atmosphere The density = 2.1 g/cm2, hence, there must be ices present

Neptune’s moon Nereid is 340 km in diameter. It has the most eccentric orbit of any moon in the Solar System. Separation from Neptune varies from 1.4 to 9.6 million km

Neptune’s moon Nereid Discovered in 1949 Not well imaged by Voyager 2, but the spacecraft discovered 6 smaller moons Most eccentric orbit of any moon in the Solar System, hence, it was probably also captured like Triton and Pluto Nereid is 340 km in diameter Its albedo is low, 0.15, so Nereid is dark like our Moon