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 10x Earth’s diameter, >300x 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 3x 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

Conflicting currents create vortices Great Red Spot, first identified in 1600s

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 9.5x Earth, mass 95x Earth, but density is only 0.7 g/cm3 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….

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 4x Earth, mass 15x 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 3.9x Earth, mass 17x – 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?

Discovered from predictions – Separately by English & French astronomers 1840s – 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