Download Lecture 12 - Seattle Central College

ASTR 100
Lecture 12: Jovian Planet Systems
Tuesday: Jovian Planets, Kuiper belt, and Oort
cloud, …Ch. 6-9
Space exploration (Not in book)and
Formation of the Solar System (Ch. 6)
Presentations….
Jovian or outer planets: Jupiter, Saturn, Uranus, Neptune
Summary:
Jovian planets considered “systems” consisting
of planet, moons, rings
Planets: composition, weather
Moons: Many, some have terrestrial-planet-like
features
Rings: They look neat.
They’re big.
…but they’re fluffy
Could fit 1,400 Earths inside Jupiter, but Jupiter is only
318 times as heavy
Composed mostly of Hydrogen and Helium
Compositional differences:
Jupiter and Saturn mostly H and He
Uranus and Neptune have greater proportion of
“volatiles”: water, methane, ammonia
- Volatiles more prevalent further away from Sun
- Jupiter and Saturn’s larger masses allowed them
to trap H and He
WTF?
metallic
hydrogen?
…Just means
Hydrogens
are sharing
electrons
Jovian planets all have high rotation rates:
(More mass means harder to stop)
≈ 17 hrs. ≈ 16 hrs.
Day ≈ 10 hrs.
≈ 10hrs.
“Metallic hydrogen”, core
metals, and high rotation
rates give all Jovian
planets awesome
magnetospheres
UV images of
Jupiter’s aurorae
from New Horizons
spacecraft flyby
(2007)
Great Red Spot is an anti-hurricane, raging for last 300
years:
Have seen similar weather on all other Jovian planets
What’s up with the different colors of clouds?
Each different “volatile” has a different color
in vapor form
What’s up with the stripes?
IR image->
Weather patterns are caused by convection of air
and rotation of planet. Jovian planets have like
400km/hr winds
Moons …so many moons
Geologic activity?
Alive or dead?
The rules of thumb for
terrestrial worlds (i.e. bigger or
smaller than Mars) don’t apply
due to differences in
composition of the Jovian
moons
The Jovian moons have very
water-rich mantles: “ice
geology” vs. “rock geology”
Io: hotbed of volcanic activity
Why hasn’t Io cooled off yet?
Tidal heating: The other moons have tugged Io’s
orbit into an more eccentic ellipse, Jupiter’s
gravity grinds Io to heat it up.
Europa: Crust of ice over a liquid water
ocean maybe 100’s of km deep
Strong candidate for
extra-terrestrial life
Ganymede and Callisto: Show cratering, must have
old surfaces
(Saturn’s large moon) Titan: Lakes of methane and
ethane, thick atmosphere
Huygens probe landed in 2005
Saturn’s medium moons: More of what one might expect
from moons - geologically dead and cratered
…mostly
Enceladus
≈ 500km
Enceladus lit up by
Saturn’s
magnetosphere?
Miranda, 570km in diameter;
5km scarps, craters, coronae, regiones, sulci
Galileo first saw “ears” on Saturn,
now know that all of the Jovian
planets have rings.
IR image->
Must be universal.
Once collisions or tides make a debris
field, it maintains itself by “grinding
down” through more frequent
collisions and “catching” new stuff
We have seen a Jovian planet, capture and rip
apart a comet, Comet Shoemaker-Levy 9, in 1994
https://www.youtube.com/watch?v=CiLNxZbpP20
IR image->
Features of rings: Gaps,
“ringlets”, gap and
shepherd moons
How do we know?
1) Sending probes
2) Earth-based telescopes (Spectroscopy)
A few of the more important missions to Jovian planets:
Voyager 1,2 (launched 1977)
Galileo (launched 1989)
Cassini (launched 1997)
New Horizons flyby (2007)
Key terms:
Jovian planets, volatiles, “metallic hydrogen”, magnetosphere,
rings, gaps, resonances, tidal forces
Key Ideas:
What are the basic parts features of a Jovian planet system?
How are Jovian planets differentiated
The weather and magnetospheres of Jovian planets
How does “ice-geology” vs. “rock-geology” make even some small
Jovian moons geologically alive?
What are the basic features and origins of ring systems in Jovian
planets?
How do we know?