Jovian Planets: Formation, Composition, and Satellites, Slides of Astronomy

Download Jovian Planets: Formation, Composition, and Satellites and more Slides Astronomy in PDF only on Docsity!

Fall, 205 Astronomy 110

Jovian Planets

Fall, 205 Astronomy 110

Jovian Planets

Bigger & more massive

Lower density, different composition

Rings

Numerous moons

Fall, 205 Astronomy 110

Jovian Planet Formation:

How Differences Arise

• TIMING: the planet that forms earliest captures the most hydrogen & helium gas.Capture ceases after the first solar windblew the leftover gas away. - LOCATION: the planet that forms in a denser part of the nebula forms its core first.

Fall, 205 Astronomy 110

Jovian Planets - Composition

Jupiter & Saturn: almostall H & He, very littlemetal & rock (

less dense

Uranus & Neptune: <50%H & He, the rest hydrogencompounds (water,methane, ammonia), withsome metal & rock (

more

dense

Jupiter Saturn Uranus Neptune

Density (g/cc)

Fall, 205 Astronomy 110

Jovian planets: Internal Structure

• No solid surface.• Layers under high pressure and temperatures. - Cores (~10 Earth masses) made of hydrogen compounds, metals & rock - The layers are different for the different planets.

Fall, 205 Astronomy 110

Layers Differ in Phase

Density of water is ~1g/cm

3

Metallic hydrogen conducts

electricity; it is not solid.

Core is hydrogen compounds,

metals, rocks. But 10 x the massof Earth inside a volume the sizeof Eath.

Jupiter

Fall, 205 Astronomy 110 Magnetic Fields

Jupiter has a powerful magnetic field generated by itsrotating, convecting layer of metallic hydrogen.

Fall, 205 Astronomy 110

The Jovian Planets: Appearance

Colorful surface features:

Bands and Clouds of differingcompositions

Complex Weather Systems

High Wind speedsStorms, some long-lived

Fall, 205 Astronomy 110

Planet colors

Saturn’s layers are the same, but deeper in and

farther from the Sun --- more subdued.

Saturn’sColors

Fall, 205 Astronomy 110

Uranus and Neptune’s upper layers are colder still,

allowing methane to condense.

Methane gas absorbs red light and transmits blue

light reflected by clouds

Fall, 205 Astronomy 110

The

Great

RedSpot • twice as wide as the Earth• Has existed for at least 3 centuries

Fall, 205 Astronomy 110

Storms Other Jovian Planets

• Saturn: even faster winds• Neptune: can see storms, but not as long

lived.

• Uranus: dull when Voyager 2 flew by, but

HST captured major storms.

– Extreme tilt means that Uranus’ southern

hemisphere may just now be getting sunshinefor the first time in decades.

Fall, 205 Astronomy 110

Medium & large

moons

Enough self-gravity to bespherical

Are or were geologically active.

Have substantial amounts of ice.

Formed in orbit around jovianplanets.

Circular, equatorial orbits insame direction as planet rotation

Fall, 205 Astronomy 110

Small moons

Far more numerous than the medium and largemoons.

Not enough gravity to be spherical: “potato-shaped”

Captured asteroids, so orbits do not follow patterns.

Orbits can be tilted, elliptical, and even backwards!