The Jovian Planets Chapter 7 Topics Jupter Saturn

The Jovian Planets Chapter 7

Topics • • • Jupter, Saturn, Uranus, Neptune How do we know? Why do we care? What is common about the outer planets? What is peculiar to each of these planets?

Jovian planets (Jupiter-like)

Size radius is about 1/10 of the radius of the Sun

Terrestrial Distance from the Sun Jovian

Terrestrial e z i S Jovian small--1/100 radius large --1/10 radius of the Sun orbit n o i t a c Lo AU at 0. 4 to 1. 5 orbit at 5 to 30 AU s n o Mo few none s g n i R n o i t i s o p Com rocks and metals many (# growing) all have rings gasses and ice

Composition 0. 71 to 1. 67 g/cm 3 So what are they made of? mostly gasses (hydrogen, helium) and ice

Jupiter • largest planet • Great Red Spot • studied by Pioneer, Voyager 1 & 2, Galileo spacecraft • liquid interior (very high pressure and temperature) • 16 moons (4 largest are the Galilean moons)

Io • Active volcanoes

Europa • subsurface ocean • cracked ice

Ganymeade • lots of faults • strong magnetic field

Callisto • old surface (meaning that it’s not undergoing lots of change except for impact craters)

Saturn • Large, thin rings • Rings are held together by the gravitational attraction of “shepharding” satellites • Major Gaps: The Cassini and Enke divisions

Titan • larger than Mercury • has an atmosphere • probably has oceans of methane

Uranus • discovered in 1781 • shows no cloud banding • axis of rotation is only tilted 8 degrees from the ecliptic • 84 year orbital period • rings originally discovered during occultation of a star • young rings (what’s the source of dust? )

Neptune • noted by Galileo • the exact path of Uranus could not be explained by the gravitational pulls of the Sun, and the other planets. What does this mean? • discovered in 1846 • 164 year orbital period • strong magnetic field

Triton • density 2. 1 g/cm 3 • atmosphere (nitrogen) • impact craters due to comets • ice made of water • active ice volcanoes • retrograde orbit (it’s going the wrong way) • probably captured by Neptune

Extrasolar planets • How many planets have we discovered besides those in our solar system? • I’m starting to lose count, but it’s now over 100. • Planets are even found in binary star systems. • We analyze the wobble in a star by studying the Doppler shift in its spectrum and determine the approximate masses and distances of the orbiting planets.

How do we know? • How do we know that the outer planets are mostly gas and mostly made up of hydrogen and helium? • How do we know that the atmosphere of a planet has methane? • How do we know the period of rotation of the outer planets? (Note: we use a different technique of measuring rotational period of the terrestrial planets. ) • How do we know that a moon’s surface is ice? • How do we know the size of matter within the rings? • How do we know that a moon has an “old” surface and that the moon has little geologic activity?