Transcript Ch 8 part II and 9 part I UNP (3-1-11)

I.
II.
Outline of Uranus, Neptune and Pluto
(Ch. 8 part II and Ch 9 part I
Not exactly like Book)
Uranus and Neptune: Discoveries,
atmospheres, interiors, rotation,
magnetic fields, moons, rings, Uranus’
axis tilt and seasons.
Pluto and Charon: Orbit, composition,
other moons, why so different from
Jovian planets?
III. Transneptunian Bodies (the Kuiper belt)
Planet Distance
Mass
Moons
Density
(AU)
(Earth = 1)
(Water =1)
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
0.39
0.72
1.0
1.5
5.2
9.5
19.2
30.1
0.05
0.9
1.0
0.11
318
95
17
17
0
0
1
2
28
18
21
8
5.43
5.25
5.52
3.95
1.33
0.69
1.29
1.64
Pluto
39.5
0.002
3
2.03
Uranus and Neptune

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
Interiors of Jovian Planets
Interiors
Question 1
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 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 later
b) 42 years later
c) 21 years later
d) In 2008
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?
Outline of Uranus, Neptune and Pluto
II.
Pluto and Charon: Orbit, composition,
other moons (Nix & Hydra), why so
different from Jovian planets?
Pluto and Charon
Discovery of Charon with
ground based telescope
Hubble Space Telescope
Pluto and its three Moons
Planet Distance
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
Mass
(AU)
(Earth = 1)
0.39
0.72
1.0
1.5
5.2
9.5
19.2
30.1
39.5
0.05
0.9
1.0
0.11
318
95
17
17
0.002
Moons
Density
(Water =1)
0
0
1
2
28
18
21
8
3
5.43
5.25
5.52
3.95
1.33
0.69
1.29
1.64
2.03
Solar Nebula
was “thinning
out hence U and
N are smaller
than J and S
and so is Pluto
and its transneptunian
relatives
Outline of Uranus, Neptune and Pluto
(Ch. 8 part II and Ch 9 part I )
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)
Question 3
Would you expect the composition of objects in
the Kuiper belt to be?
a) The same as those in the asteroid belt
b) Iron cores and silicate mantles
c) Hydrogen and helium
d) 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 belt
b) Iron cores and silicate mantles
c) Hydrogen and helium
d) None of the above
Kuiper Belt
~50 AU
•
Sun
Neptune’s Orbit
Outer Solar System
Outer Solar System
Collision in the Kuiper Belt
Paiting 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?
• Is Pluto a planet or a
• What is Pluto like?
Kuiper belt object?
Pluto is much smaller than
was called a planet by the
any other planet, with an Pluto
International Astronomical
orbit more elliptical and
Union until 2006. Its
more inclined to the
properties suggest that it is one
ecliptic plane than that of of the largest members of the
any other planet. It is
Kuiper belt objects. Its
made mostly of ices and
composition and orbital
has a very thin
properties match those of other
atmosphere of gases that
Kuiper belt objects and do not
are expected to freeze
fit in with the other planets. It
onto the surface as Pluto
was the largest known Kuiper
moves farther from the
belt object until summer 2005
Sun in its 248-year orbit.
now there is a larger one
It has 3 moons.
further out (Eris).