Goal: To compare Neptune to its neighbor Uranus
Objectives:1) To learn about its Atmosphere
2) To explore its Core3) To learn about its Moons
If time left: How the formation of the solar system affected the orbits of
the gas giants.
Voyager 2
Springtime on Neptune
Neptune in 3 D
Atmospheric make up
• Molecular hydrogen (H2) - 80.0% (3.2%)
• Helium (He) - 19.0% (3.2%)
• Methane (CH4) 1.5% (0.5%) (Uranus was 2.3%)
• Hydrogen Deuteride (HD) – 192
• Ethane (C2H6) - 1.5
• Aerosols: Ammonia ice, water ice, ammonia hydrosulfide, methane ice(?)
Neptune winds
• With little turbulence to dampen winds, the winds on the equator get as high as 1200 miles per hour.
• Neptune also emits twice as much energy in the infrared that the energy in the optical it gets from the sun.
• So, that means Neptune rains diamonds towards the core to generate heat!
Core
Rings
Moons
• Neptune has 13 known moons. Very few have images which are any good.
• Only one is large, Triton. Two are about 400 km in diameter. Rest are much smaller.
ProteusVery dark (reflects about 7% of sunlight).
120,000 km from Neptune
Outer most of Neptune’s probable original moons.
5 moons inside of Proteus’s orbit.
Nearest to Neptune is Naiad which is at 48k km from Neptune (29 km in diameter).
Triton
interesting
Triton up close!
• http://www.space.com/common/media/video/player.php?videoRef=SP_090902_triton
Triton is a captured TNO!
• TNO = Trans-Neptunian Object (an object like Pluto).
• Diameter 2700 km, which is a little smaller than our moon.
• About 10% closer to Neptune than our moon is from us.
• Its orbit is retrograde! This is a backwards orbit, which can only be if it was captured.
• However, this has some other implications…
Triton’s impact on Neptune
• Retrograde orbit means that tidal interactions with Neptune bring it CLOSER to Neptune!
• This means it was once further out, and probably tossed all of Neptune’s original moons which started further out that its current position away from Neptune.
• Eventually it will do the same to all the inner moons.
• Is probably the reason the outer moons have some very high eccentricities.
The death of Triton
• In a billion years (maybe less) Triton will get close enough to Neptune for Neptune to rip it apart.
• This will create a spectacular ring system around Neptune – even dwarfing the Saturn ring system.
• Until then, we still get to see fireworks as the volcanism on Triton caused by the Tides of Neptune continue to increase.
Conclusion:
• Neptune is similar to Uranus in many ways, the real difference being the moons because of the chaos the captured moon Triton has caused on the Neptune moon system.
