IES-04 Neptune Info

7/29/2019 IES-04 Neptune Info

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Neptune

Details


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General Information Discovered by German astronomer, J.G.Galle on Sept.23, 1846; Prior

to him, J.C.Adams (UK) and U. J.J.LeVerrier have predicted it.

Its largest moon, Triton was discovered by W. Lassell (UK) 17 days

later.

1949 Another satellite, Nereid by G.Kuiper

Neptunes ring-arcs mid-1980s

June 1989 Voyager 2 observed Neptune system. Magnetosphere

and atmosphere knowledge. Erupting geysers on Triton mapped; 6

new satellites


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Contd.

Neptune - Nearly circular orbit; 165 yr rotation time period around Sun;W-E rotation like Earth

1/3rd size of Jupiter, similar composition of Uranus

Most dense, suggesting presence of a relatively large core of heavyelements. Recent results-Low density liquid core

Abundance of methane in atmosphere. Winds at equator travel E-W with

2K km/hr.

Several types of cloud patterns; Great Red Spot at 200 South (12k km wide

counter-clockwise rotation with a period of 16 days)


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Contd.

Strong, complex magnetosphere and magnetotail; Magnetic field offset

from center and tilted by 470from rotation axis. Similar to Uranus-

Puzzling. Reversals at same time unlikely

Rings : Several rings by Voyager N63, N53 and N42 (42k km fromNeptune). The two outer rings include clumps of dust that form rings, arcs

or segments. A 4th ring mass forms a broad, diffuse sheet extending inner

Neptune system

Entire mass of ring material 10k times less than Uranus


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Satellites

8 known satellites; Largest is Triton like Earths Moon; Rest are

in the range 50-400km dia.

4 small satellites within ring system dark objects.

The largest of newly discovered satellite, Proteus outside ring

system with 1.1 earth days to complete one complete orbit.

Nereid, outermost satellite 340 km dia. ,359 days around

Neptune


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Contd. Triton: Vigorously erupting geysers. Travels in a circular synchronous orbit with

retrograde motion. Both Triton and Pluto share many characteristics (size,

composition, mass etc.)Enigma; density of 2.1gm/cc -1/3rd ice and 2/3rd rocky

materials; Methane, nitrogen ices and frost From Spectral characteristics

Two primary terrainsolder, rugged unit called cantaloupe terrain (irregular

pits&bumps and linear features), and a younger plains unit probably of volcanic

origin

Smooth plains characterized by irregular-shaped depressions (100-200km dia.)

Prominent southern ice cap of nitrogen ice. Spin axis inclination 210 w.r.t orbital

plane around Neptune, like Earth Triton also has seasons

Theory for eruptions N gas is transparent. Nitrogen ice serves as a kind of solid-

state Greenhouse solar energy trapping

Dark streaks on surface plume-producing processes common


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IES-04 Neptune Info

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