i.uranus and neptune: discoveries, atmospheres, interiors, rotation, magnetic fields, moons, rings,...
TRANSCRIPT
I. Uranus and Neptune: Discoveries, atmospheres, interiors, rotation, magnetic fields, moons, rings, Uranus’ axis tilt and seasons.
II. Pluto and Charon: Orbit, composition, other moons, why so different from Jovian planets?
III. Transneptunian Bodies (the Kuiper belt)
Outline of Uranus, Neptune and Pluto (Ch. 8 part II and Ch 9 part I Not exactly like Book)
Planet Distance(AU)
Mass(Earth = 1)
Moons Density(Water =1)
Mercury 0.39 0.05 0 5.43
Venus 0.72 0.9 0 5.25
Earth 1.0 1.0 1 5.52
Mars 1.5 0.11 2 3.95
Jupiter 5.2 318 28 1.33
Saturn 9.5 95 18 0.69
Uranus 19.2 17 21 1.29
Neptune 30.1 17 8 1.64
Pluto 39.5 0.002 3 2.03
Not known to ancient greeks, discovery details.
Composition : H, He, CH4, NH3, etc.
Atmospheres: less active, dark spot on Neptune
Interior: liquid hydrogen but no metallic hydrogen
Rotation: fast (~17 hours for both) Magnetic field: strong (but not know how it
is produced) Moons: many moons, Neptune’s Triton is
larger than Pluto and retrograde (probably captured)
Rings: dark and faint, Neptune has incomplete ring arcs
Uranus and Neptune
Interiors of Jovian Planets
Interiors
If Uranus is at its Autumnal Equinox, what does that mean?
Question 1
If Uranus it is at its Autumnal Equinox, what does that mean?
a) Nothing, Uranus has no seasons
b) The Sun is crossing Uranus’ equator from North to South
c) The Sun is at its northernmost point on Uranus
d) The Sun is in the southern hemisphere of Uranus
Question 1
If Uranus it is at its Autumnal Equinox, what does that mean?
a) Nothing, Uranus has no seasons
b) The Sun is crossing Uranus’ equator from North to South
c) The Sun is at its northernmost point on Uranus
d) The Sun is in the southern hemisphere of Uranus
Question 1
Uranus takes 84 years to orbit the Sun. In 2007 Autumn started in the northern hemisphere of Uranus, when will Winter start in the northern hemisphere of Uranus? a) 84 years laterb) 42 years laterc) 21 years laterd) In 2008
Question 2
Uranus takes 84 years to orbit the Sun. In 2007 Autumn started in the northern hemisphere of Uranus, when will Winter start in the northern hemisphere of Uranus? a) 84 years laterb) 42 years laterc) 21 years later in 2028d) In 2008
Question 2
Triton: largest of Neptune’s moons
Larger than Pluto
and in a retrograde
orbit
Triton: largest of Neptune’s moons Larger
than Pluto and in a
retrograde orbit
Why does a retrograde
orbit indicate capture?
II. Pluto and Charon: Orbit, composition, other moons (Nix & Hydra), why so different from Jovian planets?
Outline of Uranus, Neptune and Pluto
Pluto and Charon
Discovery of Caron with ground based telescope
Hubble Space Telescope
Pluto and its three Moons
Planet Distance(AU)
Mass(Earth = 1)
Moons Density(Water =1)
Mercury 0.39 0.05 0 5.43
Venus 0.72 0.9 0 5.25
Earth 1.0 1.0 1 5.52
Mars 1.5 0.11 2 3.95
Jupiter 5.2 318 28 1.33
Saturn 9.5 95 18 0.69
Uranus 19.2 17 21 1.29
Neptune 30.1 17 8 1.64
Pluto 39.5 0.002 3 2.03
Solar Nebula was “thinning
out hence U and N are smaller than J and S
and so is Pluto and its trans-
neptunian relatives
III. Transneptunian Bodies (the Kuiper belt):
Many objects smaller than planets: similar to the asteroid belt
Largest object (Eris) is slightly larger than Pluto
Source of some of the comets Triton may have formed in the
Kuiper belt was captured by Neptune (Triton’s orbit is retrograde)
Outline of Uranus, Neptune and Pluto (Ch. 8 part II and Ch 9 part I )
Would you expect the composition of objects in the Kuiper belt to be? a) The same as those in the asteroid beltb) Iron cores and silicate mantlesc) Hydrogen and heliumd) None of the above
Question 3
Would you expect the composition of objects in the Kuiper belt to be? a) The same as those in the asteroid beltb) Iron cores and silicate mantlesc) Hydrogen and heliumd) None of the above
Question 3
Kuiper Belt
•
~50 AU
Sun
Neptune’s Orbit
Outer Solar System
Outer Solar System
Collision in the Kuiper BeltPaiting by Daniel D. Durda
Is Pluto a planet or a Kuiper Belt object?
Is Pluto a planet or a Kuiper Belt object? Pluto is well beyond Neptune, in the
Kuiper Belt.
Inclined orbit is typical of Kuiper Belt objects.
Composition is typical of Kuiper Belt objects, but not like any of the other planets.
Is Pluto a planet or a Kuiper Belt comet? One Kuiper Belt object has been found that is
slightly larger Pluto’s size (Eris, a.k.a. object 2003 UB313) and several slightly smaller.
Kuiper Belt objects have similar orbital resonances with Neptune.
Kuiper Belt objects can have moons.
Triton (a captured moon of Neptune) is even larger than Pluto.
What have we learned?• What is Pluto like?Pluto is much smaller than
any other planet, with an orbit more elliptical and more inclined to the ecliptic plane than that of any other planet. It is made mostly of ices and has a very thin atmosphere of gases that are expected to freeze onto the surface as Pluto moves farther from the Sun in its 248-year orbit. It has a moons.
• Is Pluto a planet or a Kuiper belt object?
Pluto was called a planet by the International Astronomical Union until 2006. Its properties suggest that it is one of the largest members of the Kuiper belt objects. Its composition and orbital properties match those of other Kuiper belt objects and do not fit in with the other planets. It was the largest known Kuiper belt object until summer 2005 now there is a larger one further out.