Jupiter and the Jovian Planets

Formation of Jovian Planets• Step 1 Accretion of planetesimals to

form large Earth-like solid planet cores of rocks, iron, nickel

• Masses of Cores in terms of Earth’s mass Jupiter - 28 Saturn - 17 Uranus - 3.5 Neptune - 4.3• Step 2 Lighter gases condense on to

the planet cores due to gravity and cold temperatures

Jupiter – Formation of Planetary Systems

Jupiter – “A Failed Star”• Jupiter is 318 times more massive than the Earth;

yet, it is 80 times too small to become a star, i.e. make nuclear energy from fusion like the Sun

• But Jupiter (and Saturn) emits roughly twice the energy it receives from the Sun

• Energy derives from self-gravity gravitational compression of the interior (Jupiter shrinks about an inch per century)

• Surface T = 124 K, but expected 109 K (assuming Sun to be the only source)

• Jupiter radiates (124 / 109)4 = 1.7 times more energy than would be expected

MolecularHydrogen

MetallicHydrogen

“Ice”

Rock

Jupiter Interior

Conditions inside Jupiter• Composition like the Sun: mostly H, He• Atmosphere 500 miles thick, largely H2, He, and

CH4, NH3, H2O• Very low mean density of 1.33 g/cc (including

compressed core) planet must be largely liquid• “Surface” is largely top of liquid hydrogen ocean

(Jovian planets have no solid surface), where “Air pressure” is 500 x Earth’s, and temperature of 4000 F

• Equator and poles do not rotate at same rate (oblate shape): 9h 50min and 9h 55 min respectively

• Huge magnetic field, why?

Jupiter’s Interior• Most of Jupiter is about 40,000 mile deep

ocean of liquid hydrogen

• But it is mostly metallic H2: high density and pressure compress the H2 molecule so that they “share” electrons, i.e. electrons can move around like in a metal conduct electricity

• “Core” is solid ice, rock, iron, nickel at very high pressure (1 billion lbs / sq. inch)

- core itself is about 28 x Earth’s mass

- temperature 50,000 F

MolecularHydrogen Metallic

Hydrogen

“Ice”

Rock

Saturn Interior

Interiors of Jupiter and Saturn

Interiors of Uranus & Neptune

Uranus Neptune

RockyCores

Slushy“Ice”Mantles

MolecularHydrogen

MetallicHydrogen

Jupiter Saturn

Uranus Neptune

Earth

Jupiter and Saturn have metallic hydrogen mantle; Uranus and Neptune don’t

Temperature (pressure) in Jupiter rises faster than in Saturn with depth

Although T and P are high in the cores, not sufficient for nuclear fusion like starsRequire millions of degrees!

Jupiter – The King of Planets

Stripes,What are they?

The Red Spot – What is it?

First seen by Galileo, over 350 years ago ! Twice the size of the Earth

A long lasting (over 300 years!!), internally powered, cyclonic storm

(but what sustains it?)

Rapid rotation of Jupiter

Period ~ 10 hrs In spite of its size (318 times more massive than the Earth) it rotates 2 ½ times faster. But there is very little tilt of rotation axis(3 degrees) No Seasons !

Internal energy source Strong convection currents

What provides the internal energy source ? Self-gravity!

Q3, A1140, SP15, Pradhan: No Curve

Jupiter – Vital Statistics• Equatorial radius = 71,500 Kms

• Orbital period = 11.86 Earth years

• Mean density = 1.33 g/cc (3.5 times lower than Earth’s)

• Indicates mostly H2 interior, but at tremendous pressure Metallic Hydrogen (conducts electricity!), up to about 20,000 Kms into the center

• Alternating lighter and darker stripes on the surface are zones of rising (warmer) and falling (cooler) material

Vertical Convection: “Belts” and “Zones”

Cloud patterns are at different temperatures (altitudes) and wind speeds;tremendous “wind shear” (reverse direction at different altitudes)

Jovian Interior

Mostly metallic hydrogen electrically conducting interior huge magnetic field

Jovian Magnetosphere

Note that scale on bottom right! Jupiter’s magnetic field is 20,000 times stronger than Earth’s

Jupiter’s Magnetic Field• 20,000 times stronger than Earth’s, due to

convection in liquid metallic H2 interior; convection is due to rapid rotation

• “Fast electrons” produced when the solar wind hits Jupiter’s magnetosphere

• Lethal rays: density of particles is thousands of times fatal human dosage

• Magnetosphere extends up to Saturn, 5 AU away

Jupiter and the 4 Galilean Moons:Io, Europa, Ganymede, Callisto

Relative sizes of Galilean Moons

Galilean Moons: Io, Europa, Ganymede, Callisto Rocky to Icy

Io and Europa are mostly rocky but Ganymede and Callisto have more ices;Densities: 3.6, 3.0, 1.9, 1.8 g/cc respectively.

(Ganymede is the largest moon in the solar system)

Jovian Moons

• In addition to the 4 Galilean satellites, 12 other moons of Jupiter have been discovered

• Owing to Jupiter’s tidal effects all Galilean moons are ‘synchronous rotators’: they keep the same face towards Jupiter

• Voyager also found a ring around Jupiter, in between two small moons before Io

• Latest NASA probe of Jupiter is called Galileo

IO

• Closest large moon to Jupiter

• Orbital period = 42 hrs

• Surface has no impact craters, so less than 1 million years old

• Many volcanic craters – active volcanoes

• No water (too hot), but lots of sulfur on surface (sulfur condenses easily; appears black when heated)

Erupting volcanoes (taped live!)

Hot-spots at volcanoes

Io’s Volcanic Activity• Eight volcanoes seen by Voyager (many

more seen since)• Plumes rise 100 miles, spread over

hundreds of miles• Surface temp roughly 700 F near

volcanoes, -250 F away from them• Caused by Jupiter’s tidal effect large

land tides, up to 100 yards in height • Friction inside Io produces heat and

volcanic activity (“squeezed” like a ketchup bottle !)

Pizza?

Volcanic features on Io

Typical volcanic feature on Io

Io’s orbit around Jupiter:Sulfur emission (spectral lines)

Io and Jupiter’s Magnetic Field

• Magnetic field rotates with the planet, and electrifies the orbit of IO plasma (charged particles) torus surrounding orbit of IO; contains Sulfur ions S+ (emission spectral lines detected on the Earth)

Electrically charged atmosphere surrounding Jupiter and orbit of Io

Radio emission from around Jupiter- “Synchrotron radiation” at radio wavelengths is produced by “fast electrons” from the magnetosphere

- Jupiter’s radio signals are detected on the earth! Interfere with radioCommunications with CB, short-wave radio, radar, UHF TV, etc.

Europa: Ice rafts moving on liquid water oceans

Very thin Oxygen atmosphere has been detected on Europa

Comparison of Jovian Moons: Evolution due to Jupiter’s gravity

Resolution

Rocky Icy

Sizes and Distances of Galilean Satellites

Sizes relative to Earth’s Moon ( = 1): 1.1, 0.9, 1.5, 1.4 respectively

Many moons of Jupiter