Astronomy Ch. 15 Neptune

Discovery of Neptune

• JC Adams and UJ Leverrier discovered the predicted planet; Le Verrier beat Adam’s by 2 days

• They used gravitational disturbances on Uranus orbit and predicted its position within only 1 degree

Neptune is the only planet discovered using

Math and physics

Neptune is named after

Roman God of the sea

How long does it take Neptune do complete one revolution around the sun?

165.2 years

How long is a day on Neptune

16 hours long

Neptune’s Interior

• Blue/green color from CH4(Methane) in the H-rich atmosphere with clouds of methane ice

• Cloud belt strict with high speed winds

• Mantle slushy water, methane, and ammonia, mixed with hydrogen and silicates

• Small heavy element core

• Similar in size and density to Uranus, but has significant amount of heat flowing from interior

• Effective temperature -214 Celsius

• Heat may be generated by radioactive decay in the minerals in its interior

Neptune’s atmosphere

• Similar to Uranus composition

• Darker cyclonic disturbances, similar to Great red spot on Jupiter, but not long lived

• Because of Neptunes inclination,(28 degrees) it experiences seasons

• Because of planets orbital period (165 years) each season last about 41 years

• Weather is extreme and changes dramatically in spite of sunlight being 900 times dimmer in Neptune

• Winds blow at 2000 km/h

• Most extreme weather in solar system

Neptunes Magnetic Field

• 27% stronger than Earths

• Produced by rotation of the mantle not the core

• Neptunes magnetic axis is 47 degrees off the rotation axis

• Produces auroras

How many moons does neptune have?

14

• only 2 large moons (Triton and Nereid)

• they all have irregular orbits

Tritón

• perfectly circular orbit

• only moon in solar system to have a retrograde motion (it was captured)

• Extremely cold: 35 K

• Few craters, very active geologically

Nereid

• very elliptical orbit

• Prograde(regular) motion

• Moon that orbits the farthest from planet, 0.3 AU

Neptunes Rings

• 6 main rings, discovered in 1984

• Made of dusty material

• Shepherd moons keep rings in place

• One of neptunes moons produces short arcs in the outermost ring

History of Neptune

• Like uranus, probably formed near jupiter and saturn and then migrated to its current position

• Hazy atmosphere, marked by changing cloud patterns

• Significant amount of heat from interior

• Triton capture may have caused peculiar satellites

• Rings have dust and are not primordial

Discovery of Pluto

• 1930 by Clyde Tombaugh

Pluto is only __ diameter of Earths moon

65%

Plutos orbit

Inclined 17 degrees to the ecliptic

crosses neptunes orbit but will never collide

Plutos surface

Nitrogen ice with daytime temperature of 55k

• thin atmosphere

• dramatic seasons

• significant amount of albedo variation

Plutos Moons

• 5 known moons

• Charon has nearly circular orbit and is the largest

• Hydra, Nix, Kerberos, and Styx all discovered between 2005 and 2012

In 2006, pluto was classified as a

dwarf planet

dwarf planets

• they do not have enough gravitational pull to clear their neighborhood

• small, rocky bodies which originated in the Kuiper belt

• Five dwarf planets so far: pluto, eris, haumea, and makemake in Kuiper Belt. Ceres in asteroid belt

Pluto is

KBOs caught in 3:2 resonance with Neptune