Uranus, Neptune, and Pluto

Discoveries of Uranus, Neptune, and Pluto

Uranus was discovered by chance with a telescope

Neptune was found after it was predicted to exist based on perturbations in Uranus' orbit

Pluto was found after extensive searches

Searches based on supposed perturbations in Uranus' orbit

(It was thought that Pluto had an effect on both Uranus' and Neptune's

orbits and Uranus had a better known orbit at this time)

Pluto is not massive enough to have a detectable effect on Uranus'orbit

Voyager 2 Flybys of Uranus and Neptune

These missions gave us most of our information regarding radius, distance, atmosphere etc.

Uranus

No internal heat source

Few surface features due to stratospheric haze

Uranus rotates faster at the poles, short overall rotation period

Large rocky core

98° tilt to Uranus's rotation-lying on its side

Uranus

Seasons on Uranus, Fig 13.6

Why the tilt? Catastrophic grazing collision?

Neptune

More surface features than Uranus

More methane and less ammonia in atmosphere than Uranus

Internal heat source

Magnetosphere

All have magnetospheres

Generally magnetic north pole and rotation north pole are close

Generally magnetic center is centered in planet

Uranus and Neptune are exceptions

Interiors

Planets interiors drawn to scale

Relative proportions of the various internal zones

Rings

Uranus on left- discovered in 1977 by stellar occultation

Neptune on right

Uranus' Rings Up Close

Epsilon (outermost )ring, complex internal structure

Shepherd satellites (U7 and U8) affecting Epsilon ring

Satellites of Uranus and Neptune

On left, Fig 13.12, Miranda a moon of Uranus, notice fractured surface

On right, Fig 13.13, Triton, largest moon of Neptune

Retrograde orbit, water ice surface, nitrogen geysers and frost

Pluto's Orbit

Sidereal period of Pluto is 248.0 years

No danger of collision between Neptune and Pluto

Neptune and Pluto have 3:2 resonance

Pluto's orbit is 17.2⁶ to the ecliptic

Pluto

Discovery photo of Charon

High resolution HST image of Pluto and Charon

Pluto and Charon (1/6 mass of Pluto) are tidally locked to each other

Properties of Pluto and Charon

Surface temp is 50 K

Frozen methane (only planet with solid methane)

Pluto may have thin methane atmosphere

Mass, radius, and density of Pluto and Charon is are similar to icy jovian satellites

Most similar to Triton- Neptune's large satellite

Pluto and Charon's Orbit

Left- view from Earth of a series of eclipses between Pluto and Charon, Fig 13.23

Fig 13.24

Formation of Pluto

Kuiper belt object?

Kuiper belt is a region beyond outer planets filled with icy objects

Plutinos are large icy bodies near Pluto's size in Kuiper belt

Kuiper belt that was not captured (perhaps like Neptunes's moon Triton with retrograde orbit) as a moon or ejected into outer solar system like rest of Kuiper belt objects?

Probably not an escaped satellite of a Jovian planet

Is Pluto a "True" Planet

Highly eccentric orbit

Small size compared to other Jovian planets

Neither terrestrial nor jovian in composition

Kuiper belt object?

Kuiper belt is a region beyond outer planets filled with icy objects

Plutinos are large icy bodies near Pluto's size

Who "Owns" or "Claims" Planets?

Treaty that no one can claim

Planets

Moons

Stars