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Home , Outline of Saturn, Rings of Jupiter, Shepherd moon

Northeastern Illinois University

Jovian

Greg Anderson Department of Physics & Northeastern Illinois University

Winter-Spring 2020

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 1 / 81 Northeastern Illinois Outline University

Overview Jovian Planets Jovian Ring Systems Review

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 2 / 81 Northeastern Illinois University

Outline

Overview Orbital Periods

Jovian Planets

Jovian Moons

Ring Systems Review Overview

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 3 / 81 Northeastern Illinois Orbital Properties of Planets University

Name Distance (AU) Period (years) Speed (AU/yr) 0.387 0.2409 10.09 0.723 0.6152 7.384 1.0 1.0 6.283 1.524 1.881 5.09 5.203 11.86 2.756 9.539 29.42 2.037 19.19 84.01 1.435 30.06 164.8 1.146

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 4 / 81 M J S

M J U

S M J

N Northeastern Illinois University

Outline

Overview

Jovian Planets Jovian Planets Planetary Densities Composition Composition H & He Formation Escape Velocity Jovian Planets Formation 2 Q: Jovian Interiors Jovian Densities 02A 02 Q: Jupiter and Saturn Q: Jupiter’s composition Jovian Interiors Jovian Interiors Jupiter Jupiter Lithograph Jupiter Jupiter Jupiter from Interior c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 6 / 81 Northeastern Illinois Jovian Planets University

Jupiter Saturn Uranus Neptune 3 d⊙ R⊕ M⊕ ρ (g/cm ) tilt T (K) Jupiter 5.20 AU 11.21 317.9 1.33 3.1◦ 125 Saturn 9.54 AU 9.45 95.2 0.71 26.7◦ 75 Uranus 19.19 AU 4.01 14.5 1.24 97.9◦ 60 Neptune 30.06 AU 3.88 17.1 1.67 29.◦ 60

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 7 / 81 Northeastern Illinois Planetary Densities (ρ = M/V ) University

5.52 5.43 5.24 5.0

4.0 3.92 ) 3

3.0

2.0 Density (g/cm

1.0 Mercury Venus Earth Mars Saturn Uranus Neptune tNOs 0.0 Jupiter

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 8 / 81 Northeastern Illinois Composition of Jovian Planets University • Hydrogen: H • Helium: He • Hydrogen Ices:

Water (H2O) Ammonia (NH3) Methane (CH4)

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 9 / 81 Northeastern Illinois Jovian Composition University

• Jupiter and Saturn – mostly H and He gas – cores of hydrogen compounds, with some rock & metal

• Uranus and Neptune

– Mostly hydrogen compounds: water (H2O), methane (CH4) ammonia (NH3) – Some H, He, rock, metal

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Northeastern Illinois Jovian Planet Formation University

• Hydrogen compounds were more abundant in the solar nebula than rock/metal. • Beyond the frost line, planetesimals could accumulate ice. • Jovian planets grew bigger and acquired H/He atmospheres.

• The Jovian cores are very similar: ≈ 10M⊕ • The biggest difference between Jovian planets is the amount of H/He gas accumulated.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 12 / 81 Northeastern Illinois Escape Velocity University

Escape velocity:

2GM v = esc r R Thermal velocity:

3T v ∼ rms r m Loss of atmospheric component: 1 v > v rms 6 esc

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 13 / 81 Northeastern Illinois Jovian Planet Formation II University

Why did Jupiter and Saturn capture more H and He gas?

Location: Planets that form in denser parts of the nebula form their cores first. Timing: The planet that forms earliest captures the most hydrogen and helium gas. Capture ceases after the first solar blows the leftover gas away.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 14 / 81 Northeastern Illinois Q: Jovian Interiors University

Why do the Jovian planet interiors differ?

A) The more distant planets formed in a cooler region of the solar nebula and therefore contain a greater proportion of ices than the closer Jovian planets.

B) They differ due to giant impacts at the late stages of planet formation.

C) Accretion took longer further from the , so the more distant planets formed their cores later and captured less gas from the solar nebula than the closer Jovian planets.

D) The more distant planets had longer to form than the closer planets, since the solar nebula lasted longer at greater distances from the Sun.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 15 / 81 Northeastern Illinois Q: Jovian Interiors University

Why do the Jovian planet interiors differ?

A) The more distant planets formed in a cooler region of the solar nebula and therefore contain a greater proportion of ices than the closer Jovian planets.

B) They differ due to giant impacts at the late stages of planet formation.

C) Accretion took longer further from the Sun, so the more distant planets formed their cores later and captured less gas from the solar nebula than the closer Jovian planets.

D) The more distant planets had longer to form than the closer planets, since the solar nebula lasted longer at greater distances from the Sun.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 15 / 81 Northeastern Illinois Jovian Densities University

1.5

) Uranus and Neptune are denser 3 than Saturn because they have . 1 0 proportionately less H/He. (g/cm

ρ The greater mass of Jupiter com- 0.5 presses the planet.

0 Saturn Uranus Jupiter Neptune

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Northeastern Illinois Q: Jupiter and Saturn University

Why is Saturn almost as big as Jupiter, despite its smaller mass?

A) Jupiter’s greater mass compresses it more and increasing its density.

B) Saturn’s rings make the planet look bigger.

C) Saturn is further from the Sun, thus cooler, and therefore less compact.

D) Saturn has a larger proportion of hydrogen and helium than Jupiter, and is therefore less dense.

E) Jupiter’s strong magnetic field constrains its size.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 19 / 81 Northeastern Illinois Q: Jupiter and Saturn University

Why is Saturn almost as big as Jupiter, despite its smaller mass?

A) Jupiter’s greater mass compresses it more and increasing its density.

B) Saturn’s rings make the planet look bigger.

C) Saturn is further from the Sun, thus cooler, and therefore less compact.

D) Saturn has a larger proportion of hydrogen and helium than Jupiter, and is therefore less dense.

E) Jupiter’s strong magnetic field constrains its size.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 19 / 81 Northeastern Illinois Q: Jupiter’s composition University

Overall, Jupiter’s composition is most like that of: A) Sun B) Earth C) D) Asteroids

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 20 / 81 Northeastern Illinois Q: Jupiter’s composition University

Overall, Jupiter’s composition is most like that of: A) Sun B) Earth C) Comets D) Asteroids

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 20 / 81 Northeastern Illinois Jovian Interiors University

+ c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 21 / 81 Northeastern Illinois Jovian Interiors University

• No solid surface • Layers under high pressure and temperatures • Heat from sun and interiors. Jupiter, Saturn and Neptune emit more energy than they receive. Jupiter and Neptune are contracting. • All four have similar cores (∼ 10 Earth masses) made of hydrogen compounds, metals, and rock • Differences in layers that surround the core.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 22 / 81 Northeastern Illinois Jupiter University

• Mostly H/He. • No solid surface. • Distance 5.20 AU.

• M = 318MEarth

• R = 11.2REarth • ρ =1.33 g/cm3 • ≥ 79 moons, rings

• Tcloud top = 125 K.

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Image Credit: NASA, ESA

Northeastern Illinois University

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Northeastern Illinois Saturn University

• Mostly H/He. • No solid surface • Distance 9.54 AU

• M = 95.2MEarth

• R =9.4REarth • ρ =0.7 g/cm3 • ≥ 82 Moons, rings

• Tcloud top = 95 K. Animation: Saturn’s Rings

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Titan Transits Saturn Northeastern Illinois Uranus University

• Hydrogen compounds, H, He • Distance 19.2 AU

• M = 14.5MEarth

• R =4.0REarth • ρ =1.32 g/cm3 • > 27 Moons, rings

• Tcloud top = 60 K. • planet, rings, moons tipped on side

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 35 / 81 Uranus & Ariel NASA Photo: Uranus with Northeastern Illinois Neptune University

• Hydrogen compounds, H, He • Distance 30.1 AU

• M = 17.1MEarth

• R =3.9REarth • ρ =1.64 g/cm3 • > 13 Moons, rings

• Tcloud top = 60 K. • Triton’s retrograde orbit.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 38 / 81 Northeastern Illinois Neptune Seasons (HST) University

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Northeastern Illinois University

Outline

Overview

Jovian Planets

Jovian Moons Selected Moons Moons Classified By Orbit Moons Classfied by Size Jupiter and Moons Jovian Moons Jupiter’s Moons Galilean Moons Io Tidal Heating Life on Europa? & Callisto Saturn’s Largest Moons Saturn Moons & Rings Saturn Satellites and Ring Structure Enceladus c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 43 / 81

Northeastern Illinois Moons Classified By Orbit University

Regular Moons: Orbits relatively close to the planet, prograde, little or eccentricity. Typically formed about their primary from the planetary sub-nebula. Irregular : Orbits are distant, eccentric, inclined, a mixture of prograde and retrograde orbits. Irregular moons were probably captured by their parent planets.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 45 / 81 Northeastern Illinois Moons Classfied by Size University

Medium (300-1500 km) & Large Moons (> 1500 km): • Enough self-gravity to be spherical. • Have substantial amounts of ice. • Formed in orbit around Jovian planets. • Circular orbits in same direction as planet rotation. • Large moons -Ongoing geological activity. • Medium-sized moons, Geological activity in past. Small Moons (< 300 km): • Far more numerous than medium and large moons. • Not enough gravity to be spherical: potato-shaped. • No geological activity.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 46 / 81 Jupiter’s Regular Moons

1:1 2:1 4:1 Io Europa Ganymede Callisto

Moons magnified 2X Northeastern Illinois Jupiter’s Moons University

Jupiter has at least 67 moons: 8 regular + 59 irregular.

Ganymede 38% Callisto 27% Europa 12% Io 23%

The four Galilean moons comprise all but .003% of the total orbiting mass.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 48 / 81 Northeastern Illinois Galilean Moons University

Four Galilean Moons (1610): • Io: Active volcanoes • Europa: Subsurface ocean? • Ganymede: Solar system’s largest moon • Callisto: cratered ice-ball

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 49 / 81 Northeastern Illinois Galilean Moons University

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Callisto. Europa Northeastern Illinois Tidal Heating University

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 54 / 81 Northeastern Illinois Life on Europa? University

• Surface mostly solid water ice. • Hypothesis: ocean of liquid water below the surface • Good place to look for life: liquid water + energy from tidal heat- ing.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 55 / 81 Northeastern Illinois Ganymede & Callisto University

Evidence for subsurface oceans on Ganymede, Callisto, but less tidal heating energy available. Did life find a way?

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 56 / 81 Northeastern Illinois Saturn’s Largest Moons University

Saturn has 24 regular and 38 irregular satellites. Seven of the satellites moons are medium and large moons, the largest Titan is bigger but less massive than Mercury. c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 57 / 81 Saturn’s Major Rings and Moons

F

B

Tethys

Enceladus

C

A

Moons magnified 10X Saturn’s Major Rings and Moons

F B Mimas Rhea

Enceladus C Dione Titan A

Moons magnified 10X Saturn’s Major Rings and Moons

Tethys Mimas Rhea FB CA EnceladusDione Titan

Moons magnified 10X Copyright: NASA/JPL/Caltech, Illustration by David Seal Enceladus Saturn’s Enceladus Titan Titan: Liquid hydrocarbons. Six Largest

Puck, Miranda, Ariel, Umbriel, Titania, Oberon Uranus’s Major Moons and Rings

Ariel Miranda Umbriel Titania Oberon rings

Moons magnified 2X Neptune rings and moons

Triton

rings moons Neptune rings and moons

moonsrings Triton Neptune rings and moons

moonsrings Triton Neptune rings and moons

moonsrings Triton Northeastern Illinois University

Outline

Overview

Jovian Planets

Jovian Moons

Ring Systems Ring Systems Saturn’s Rings Saturn’s Rings Ring Systems Saturn’s Rings Jupiter Rings Uranus Rings Uranus Rings Neptune Rings Q: Saturn’s Rings Further Study

Review

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 67 / 81 Northeastern Illinois Ring Systems University

• All four Jovian planets have ring systems. • Proposals for creation: 1. Material from protoplanetary disk inside the Roche limit. 2. Debris from moon(s) disrupted by impacts. 3. Debris from moons(s) disrupted by tidal stresses when they passed inside the Roche limit. 4. Ejecta from volcanoes on moons.

• Shepherd moons & orbital resonances : a moon orbiting near the edge of a planetary ring.

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 68 / 81 Image Credit: astronoo.com Saturn’s Rings & Eclipsed Sun from Cassini spacecraft Northeastern Illinois Saturn’s Rings University

• Most extensive in Solar System

• 99.9% H20 ice • Main rings thickness: 10m . thickness . 1km • Main rings 1cm . particle size . 10m • “Gaps” regions of low density produced by i) moons or obital resonances. • Origin: old? young? no concensus.

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Northeastern Illinois Jupiter Rings University

Rings of Jupiter, Keck telescope IR . Jupiter’s rings are faint

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Composite Image: Northeastern Illinois Q: Saturn’s Rings University

How thick are Saturn’s rings from top to bottom? A) a few million kilometers B) a few tens of thousands of kilometers C) a few hundred kilometers D) a few kilometers E) a few tens of meters to a kilometer

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 77 / 81 Northeastern Illinois Q: Saturn’s Rings University

How thick are Saturn’s rings from top to bottom? A) a few million kilometers B) a few tens of thousands of kilometers C) a few hundred kilometers D) a few kilometers E) a few tens of meters to a kilometer

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 77 / 81 Northeastern Illinois Further Study University

• Ganymede Global Map (YouTube) • Red Spot Jupiter Red Spot (Video • Jupiter Video

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 78 / 81 Northeastern Illinois University

Outline

Overview

Jovian Planets

Jovian Moons

Ring Systems

Review Review Review II Review

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 79 / 81 Northeastern Illinois Review University

• How do the density, mass and composition of Jovian planets compare to terrestrial planets? • Describe how and why the composition of Jovian planets differ. • What objects in the solar system are mostly made of hydrogen and helium? • How does the magnetic field of Jupiter compare to Earth? • What makes Jupiter denser than Saturn? • What gives Neptune and Uranus a blue color?

c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 80 / 81 Northeastern Illinois Review II University

• What are the names of the four Galilean ? • Why are icy moons more likely to be geologically active than rocky moons? • What mechanism is responsible for most of the internal heat on Io? • Which Jovian planets have rings? • How thick are Saturn’s rings? What are they made of? • What are the differences between regular and irregular moons?

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