Neptune

1
Neptune

• The Farthest Planet

www.nix.larc.nasa.gov
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Planetary Math

• Take the set of numbers
• Apply the function to each element in the set

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Planetary Math
x
0
3
6
12
24
48
96
192

0.4
0.7
1
1.6
2.8
5.2
10.0
19.4

0.387
0.723
1.000
1.524
2.800
5.203
9.539
19.18
Object
Mercury
Venus
Earth
Mars
Asteroid Belt
Jupiter
Saturn
Uranus
Mean Distance in AU
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Planetary Math

• Next number in the series
• 384

Object Mean distance from Sun in AU
Neptune 30.06 38.8
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Titius-Bode Law

• Law that was believed to predict location of
  planets in the solar system
• Accurately predicted Uranus but fell apart once
  Neptune was discovered
• Coincidental number series

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Discovery

• Only planet discovered by math
• John Couch Adams
• Urbain Jean Joseph Le Verrier
• Visual Discover
• September 23, 1846
• Johann Gottried Galle
• Galileo

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Collecting Data

• Prior to 1980s
• Earth based observations
• Telescopic
• Spectrograph analysis

Hubble Space Telescope Images 1994 www.hubblesite.
org
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The Voyager Encounter

• Voyager 2
• Science package confirmed and enhanced knowledge
• Closest Approach
• August 24, 1989
• 3000 miles from atmosphere

Voyager 2 Launch www.nix.larc.nasa.gov
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General Information

• Mass 1.02 x 1026 kg (Earth 5.97 x 1024 kg)
• Density 1.46 g/cm3 (Earth 5.51 g/cm3)
• Volume 6.25 x 1013 km3
• Escape Velocity 25 km/sec
• Surface Gravity 1.19 that of Earth
• Albedo 0.35
• Average distance from Sun 30.06 AU
• Orbital Period 164.79 years
• Period of Rotation 16 hours 3 minutes

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http//solarsystem.jpl.nasa.gov/multimedia/gallery
/Neptune_Int.jpg
http//solarsystem.jpl.nasa.gov/multimedia/gallery
/Neptune_Int.jpg
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Inside Neptunes Core
Atmospheric pressure weight of planet
Core 10,000 K
Heat escaping Core makes Neptune active. Vast
currents of hot material rise and carry Heat to
warm gaseous envelope from below.
Neptune radiates more than 2-3 more times energy
than it receives from Sun.
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Composition

• Therefore In this environment materials are
  mixed well.
• Ice invades atomic structure of Rock
• Rock dissolves in Ice
• Gas penetrates both Ice and Rock freely.

13
http//solarsystem.jpl.nasa.gov/multimedia/gallery
/Neptune_Int.jpg
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Mantel

• Composition
• Water, rocks, ammonia, and methane ices
• Heat radiating from the core
• Heats water to about 4700C
• Great pressure
• Keeps the water in liquid form
• Does not allow molecules to expand

15
Atmosphere

• Composition
• Hydrogen, helium, methane gas
• We can see the upper part of this layer
• Why is the planet blue?
• Methane absorbs red and orange wavelengths
• Atmosphere scatters blue wavelengths

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Features

• The Great Dark Spot
• Similar to Great Red Spot (Jupiter)
• Earth sized
• The Little Dark Spot
• Dark Spot 2
• Moon sized
• Taken by Voyager 2

http//encarta.msn.com/media_701611527_761577112_-
1_1/Neptune.html
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Rotational Speeds

• Great Dark Spot
• 18.3 hours
• Little Dark Spot
• 16.0 hours
• Hard to determine rotational period w/o solid
  surface
• Using magnetic field
• 16.11 hours

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Winds and Heat

• Westward (Clockwise)
• Opposite that of its rotation
• Sustained 725 mph
• Gust up to 1,250 mph
• Radiates 2.7 time the heat
• Farther from the sun then Uranus
• Top cloud layer a few degrees warmer

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Great Dark Spot Today?

• In 1994 Hubble telescope showed that the storm
  had disappeared
• Reasons
• Dissipated
• Altered by atmosphere to point were we cannot
  detect it

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Upper Atmosphere

• Cloud tops
• White parts reside
• Have photographed shadows
• Taken by Voyager 2

http//photojournal.jpl.nasa.gov/catalog/PIA01995
http//photojournal.jpl.nasa.gov/catalog/PIA02245
21
Neptunes Magnetic Field

• There must be a region within the planet that is
  liquid.
• Region must be electrically conducting.
• There must be an energy source that sets the
  region in motion and then keeps it moving.
• Rate of interior rotation Periodic radio waves
  generated from field 16 hours, 7 minutes.

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Neptunes Magnetic Field

• Tilted 47 degrees/offset 0.55 radii
• Therefore dynamo electric currents must be
  relatively closer to surface than Earth, Jupiter
  or Saturn.
• Field Strength Varies
• 0.1 Gauss (Northern)
• 1.0 Gauss (Southern)
• Polarity Jupiter and Saturn
• Goes through dramatic changes as planet rotates
  in the solar wind.

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Auroras

• Over wide regions of planet not just poles.
• Because distance from Sun
• Aurora power 50 million Watts
• Earth 100 Billion Watts

www.nix.larc.nasa.gov
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Moons

• 13 Moons total
• 2 known prior to Voyager 2
• Triton discovered in weeks after Neptunes
  discovery
• Nereid

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Moons

• 6 discovered by Voyager 2
• Naiad, Thalassa, Despina, Galetea, Larissa,
  Proteus
• 5 discovered in 2002
• Psamathe, S/2002 N1,
• S/2002 N2, S/2002 N3,
• S/2002 N4

Voyager 2 Image of a moon www.nix.larc.nasa.gov
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Triton

• Retrograde Orbit
• Slowing down
• Origins
• Believed to be captured
• Developed in system
• Interaction with outside body

Triton from Voyager 2 www.nix.larc.nasa.gov
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Triton

• One of three active bodies
• Volcanoes of nitrogen, methane, dust
• Instantly freezes and falls back as snow

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Nereid

• Highly elliptical orbit
• Fits with idea that an outside body interfered
  with the orbit or a captured object
• Takes almost one year to orbit

CGI of Nereid and Neptune http//en.wikipedia.org/
wiki/ImageNereidsim.jpg
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Rings

• 1980s discovered ring arcs
• Dense areas of partial rings
• Found when Neptune passed in front of background
  star

Neptunes Rings www.nix.larc.nasa.gov
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Rings

• Voyager 2
• Found 5 complete rings
• Observed ring arcs
• Dense portions of complete rings
• Caused by gravity from Galetea
• Rings Galle, Le Verrier, Lassell, Arago, Adams
• Ring Arcs Liberty, Equality, Fraternity