1. Jupiter

Voyager 1 & 2 (1979)
Galileo (1995) - last December!!!

1/1000th (10^-3) the mass of the Sun

Mass and size density

Mostly made of hydrogen (H) and helium (He) with a small, rocky, molten core

Red Spot:

4 x size of Earth,
more than 200 year-old cyclone

Jupiter has a ring!

Galilean Moons:

Callisto, Euorpa, Ganymede, Io

A miniature solar system with Jupiter as the 'sun'

Each moon is very different

Io:

Strong tidal forces due to Jupiter's gravity heats Io's core and produces volcanic activity

2. Saturn

Voyager 1 & 2 (1980, 1981)

mass and size density

Mostly made of hydrogen (H) and helium (He) with a small, rocky, molten core

Rings are transparent if seen 'straight on' (i.e. from directly above or below)

made of tiny particles (tiny on scales of planets!)

Rings were formed when ...

- moons strayed too close (ripped apart by tidal forces), or

- material formed too close to coalesce into a moon

Extensive moon system, like Jupiter

The Saturn system is also like a mini solar system, with Saturn as 'sun'

Titan, a moon of Saturn:

Bigger than Mercury (and, has atmosphere)

Are Saturn's rings analogous to the asteroid belt in our solar system that lie between Mars and Jupiter?

3. Uranus

Voyager 2 (1986)

Discovered in 1781 (Herschel)

Just visible to naked eye

Has rings!

Spin axis tipped on its 'side.'

- spin axis points in its orbital plane about the sun

- so too are its moons' orbits.

Why is there such an extreme tilt?

4. Neptune

Voyager 2 (1989)

Invisible to naked eye

Discovered by inference:

gravitational effects on Uranus' orbit

Has rings!

Large moon, Triton ...

has nitrogen & methane atmosphere...

... but appears cold and dead.

(a) Jupiter and Saturn

(b) just Saturn

(c) Saturn and Uranus

(d) Saturn and Neptune

(e) all of the above

(a) They have rocky cores.

(b) Their chemical composition is wrong.

(c) Their moon systems are too complex to allow nuclear fusion to begin.

(d) They are not massive enough.

(e) Their atmospheres are too thick to let light through.