Unit 7 The Outer Planets Mr Ross Brown
Unit 7: The Outer Planets Mr. Ross Brown Brooklyn School for Law and Technology
In this unit we will learn about: • Characteristics of the outer planets, how they compare to each other & to the inner planets • The internal sources of heat of these planets • Jupiter’s Great Red Spot • Why Uranus and Neptune appear blue • The moons of the gas giants • Why some of these moons appear geologically active • The rings around the gas giants
Why name it after Jupiter? • 11 January 2016 • Do now: How do Jupiter’s mass, diameter, and density compare to the Earth’s?
Why name it after Jupiter? • Jupiter, king of the gods • Largest planet in our Solar System, mass and diameter • Mass > all other planets combined • 10 x Earth’s diameter, >300 x mass
Why name it after Jupiter? • Atmosphere: mostly Hydrogen, Helium, and hydrogen-rich Methane (CH 4, ) Ammonia (NH 3, ) and Water (H 2 O) • Clouds of H 2 O ice and NH 3 • Clouds spin over planet faster than on Earth • Jupiter rotates once every 10 hours, equator bulges
Jupiter’s Interior • All based on theory • Mass calculated by observing gravitational attraction on moons • Once we calculate radius we can obtain volume, and thus density • Jupiter’s is 1. 3 g/cm 3) (Water is 1, Earth is 5. 5) • Composed of light elements (H 2)
Jupiter’s Interior • Tremendous gravity holds it all together • Deep inside compressed to 3 x density of iron
Jupiter’s Interior
Jupiter’s atmosphere • Jupiter’s heat radiates up to space, cools and drops in convection currents. • Jupiter’s speedy rotation produces a strong Coriolis effect • Strong winds, > 300 kpm (200 mph)
Coriolis Effect
Coriolis Effect on Jupiter
Coriolis Effect on Jupiter • Conflicting currents create vortices • Great Red Spot, first identified in 1600 s
Jupiter’s Magnetic Field • Convection of metallic liquid hydrogen core magnetic field much stronger than Earth’s
Jupiter’s Magnetic Field • Aurora
Jupiter’s Rings • Very thin, hard to see • Tiny particles of rock dust held by gravity
Jupiter’s Moons • Galilean moons (Io, Europa, Ganymede, Callisto) are very large – All but Europa are larger than our Moon – Ganymede is largest moon in our Solar System – Amalthea, 5 th largest, is much smaller
Io • Closest to Jupiter • Between Jupiter and Europa, tremendous tidal forces generate heat volcanoes (sulfurs)
Europa • Smallest Galilean moon • Crust of ice, cracked, with frozen mineral-rich water seeping through cracks
Ganymede and Callisto • Appear like our Moon but surface is mostly ice • Callisto may have water like Europa
Galilean Moon Densities are Highest
Jupiter’s Other Moons • Much smaller, most likely captured asteroids • Tilted orbits
Homework #12 • 12 January 2016 • If Jupiter were moved closer to the Sun, what do you think would happen to it?
Why name it after Saturn? • 19 January 2016 • Do now: How do Saturn’s mass, diameter, and density compare to Earth’s?
Why name it after Saturn?
How does Saturn differ from Earth? • 2 nd largest in solar system, twice as far from Sun as Jupiter (10 AU) • Diameter 9. 5 x Earth, mass 95 x Earth, but density is only 0. 7 g/cm 3 • Largely hydrogen & hydrogen-rich compounds
About those rings…. • Very wide, very thin – From 30, 000 km above atmosphere to 136, 000 km – Only a few hundred meters thick – And very small (centimeters) particles
About those rings….
About those rings…. • Gaps – Caused by gravity of tiny moons orbiting Saturn – Shepherding satellites: two moons in a close, common orbit
Homework #13 • 19 January 2016 • What are the rings of Saturn made of? How do astronomers know this?
Where do planetary rings come from? • 20 January 2016 • Do now: Where indeed do planetary rings come from?
Where do planetary rings come from? • Not just Saturn – Easier to see from side of planet away from Sun • How old are they? – From planet’s origin or trapped particles? – Why not clump and form a moon?
Why didn’t Saturn’s rings become a moon? • The Roche Limit – If a moon gets too close to a planet, gravity could rip it apart – The point where this occurs is 2. 44 planetary radii, called the Roche Limit
Saturn’s Moons • One very large and 61 smaller
Saturn’s Moons
Saturn's Moons • Less dense than Galilean moons – Ice interior? • Most are heavily cratered meaning……?
• 21 January 2016 • Do now: What have we learned about the Outer, or Jovian, or Gas Giant planets?
What’s so special about Uranus? • 22 January 2016 • Do now: Why does Uranus appear blue?
What’s so special about Uranus? • Diameter 4 x Earth, mass 15 x • 19 AU from Sun • 1781, first observed by Herschel – First thought it was a comet
What’s so special about Uranus? • Of course, rich in hydrogen – Water, ammonia, methane – Methane gas absorbs red light, thus Uranus appears blue • Density 1. 27 g/cm 3 – Compare to Jupiter and Saturn
What’s so special about Uranus? • That tilt, tho! – Equator almost perpendicular to orbit
Uranus’ Tilt
Uranus’ Moons • 5 large moons and about 20 smaller
What does our study of the other planets tell us about Neptune? • 25 January 2016 • Do now: What are the principal components of Neptune’s atmosphere? And what can you predict about its inner structure?
What does our study of the other planets tell us about Neptune? • Similar to Uranus in size – Diameter 3. 9 x Earth, mass 17 x – Blue – 30 AU from Sun, so hard to study • Voyager 2 mission 1989 – Encircled by bands – Large dark blue spot • Perhaps no longer there today
What does our study of the other planets tell us about Neptune?
What does our study of the other planets tell us about Neptune? • Discovered from predictions – Separately by English & French astronomers 1840 s – Saw that Uranus didn’t follow a predicted orbit, so they knew something was there
What does our study of the other planets tell us about Neptune? • Structure similar to Uranus – Planet is a hot mixture of ammonia, water, & methane – Atmosphere is hydrogen/ hydrogen compounds – Density 1. 67 – Light atoms but as core of silicon and iron
What does our study of the other planets tell us about Neptune? • Atmosphere – Blue, so methane atmosphere – Cloud bands • Coriolis effect, rotates every 16 hours – Winds over 2200 km/ hour at equator • Radiates energy, perhaps from its creation, creating convection
Neptune’s Moons • 6 small moons in close, circular orbit, and 7 much further away • Triton, as big as Jupiter’s Europa, orbits backwards (clockwise) – From Kuiper Belt? • So massive it has its own atmosphere!
Triton Streaks from geysers
Comparison of Solar System Objects
- Slides: 51
