Northeastern Illinois University Jovian Planets Greg Anderson Department of Physics & Astronomy 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 Moons Ring Systems Review c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 2 / 81 Northeastern Illinois University Outline Overview Orbital Periods Solar System 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) Mercury 0.387 0.2409 10.09 Venus 0.723 0.6152 7.384 Earth 1.0 1.0 6.283 Mars 1.524 1.881 5.09 Jupiter 5.203 11.86 2.756 Saturn 9.539 29.42 2.037 Uranus 19.19 84.01 1.435 Neptune 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 Io 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 Asteroids 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 Planet 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 c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 10 / 81 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 wind 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 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 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 c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 16 / 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 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) Comets 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. c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 23 / 81 Image Credit: NASA, ESA Northeastern Illinois Magnetosphere University c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 29 / 81 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 c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 32 / 81 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 Aurora 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 c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 39 / 81 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 Galilean Moons Io Callisto Europa Tidal Heating Life on Europa? Ganymede & Callisto Saturn’s Largest Moons Saturn Moons & Rings Saturn Satellites and Ring Structure Enceladus Enceladus c 2012-2020 G. Anderson Universe: Past, Present & Future – slide 43 / 81 Titan Northeastern Illinois Moons Classified By Orbit University Regular Moons: Orbits relatively close to the planet, prograde, little orbital inclination or eccentricity. Typically formed about their primary from the planetary sub-nebula.