Astronomy a beginners guide to the universe 8th CHaisson mcmillan chapter 08

Astronomy A BEGINNER’S GUIDE TO THE UNIVERSE EIGHTH EDITION CHAPTER Moons, Rings, and Plutoids Lecture Presentation © 2017 Pearson Education, Inc Chapter Moons, Rings, and Plutoids © 2017 Pearson Education, Inc Units of Chapter • • • • • • The Galilean Moons of Jupiter The Large Moons of Saturn and Neptune The Medium-Sized Jovian Moons Planetary Rings Beyond Neptune Summary of Chapter © 2017 Pearson Education, Inc 8.1 The Galilean Moons of Jupiter • All four Jovian planets have extensive moon systems, and more are continually being discovered • The Galilean moons of Jupiter are those observed by the astronomer Galileo in 1610: Io, Europa, Ganymede, and Callisto © 2017 Pearson Education, Inc 8.1 The Galilean Moons of Jupiter • This image shows Jupiter with two of its Galilean moons © 2017 Pearson Education, Inc 8.1 The Galilean Moons of Jupiter • The Galilean moons and their orbits © 2017 Pearson Education, Inc 8.1 The Galilean Moons of Jupiter • Their interiors © 2017 Pearson Education, Inc 8.1 The Galilean Moons of Jupiter • Io is the densest of Jupiter’s moons, and the most geologically active object in the solar system – – – It has many active volcanoes, some quite large Io can change surface features in a few weeks Io has no craters; they fill in too fast Io has the youngest surface of any solar system object © 2017 Pearson Education, Inc 8.1 The Galilean Moons of Jupiter • Io is very close to Jupiter and also experiences gravitational forces from Europa The tidal stretching is huge, and provides the energy for the volcanoes © 2017 Pearson Education, Inc 8.1 The Galilean Moons of Jupiter • Europa has no craters; surface is water ice, possibly with liquid water below • Tidal forces stress and crack ice; water flows, keeping surface relatively flat © 2017 Pearson Education, Inc 8.4 Planetary Rings • The Roche limit is where the tidal forces of the planet are too strong for a moon to survive; this is where rings are formed © 2017 Pearson Education, Inc 8.4 Planetary Rings • All observed ring systems are within this limit © 2017 Pearson Education, Inc 8.4 Planetary Rings • • Voyager probes showed Saturn’s rings to be much more complex than originally thought Earth is shown on the same scale as the rings © 2017 Pearson Education, Inc 8.4 Planetary Rings • “Shepherd” moons define the edges of some of the rings © 2017 Pearson Education, Inc 8.4 Planetary Rings • Jupiter has been found to have a small, thin ring © 2017 Pearson Education, Inc 8.4 Planetary Rings • Uranus has nine thin rings The inset (top) shows the Epsilon ring © 2017 Pearson Education, Inc 8.4 Planetary Rings • Two shepherd moons keep the Epsilon ring of Uranus from diffusing away © 2017 Pearson Education, Inc 8.4 Planetary Rings • Neptune has five rings, three narrow and two wide © 2017 Pearson Education, Inc 8.5 Beyond Neptune • Pluto was discovered in 1930 It was thought to be needed to explain irregularities in the orbits of Uranus and Neptune, but it turned out that there were no such irregularities © 2017 Pearson Education, Inc 8.5 Beyond Neptune • • • Pluto’s moon, Charon, was discovered in 1978 It is orbitally locked to Pluto, and about a sixth as large Pluto also has four smaller moons: Nix, Hydra, Styx, and Kerberos © 2017 Pearson Education, Inc 8.5 Beyond Neptune • Charon’s orbit is at an angle of 118º to the plane of Pluto’s orbit © 2017 Pearson Education, Inc 8.5 Beyond Neptune • The first Kuiper belt objects were observed in the 1990s, and more than 1200 are now known Some of them are comparable in size to Pluto • These images show Eris and its moon Dysnomia © 2017 Pearson Education, Inc 8.5 Beyond Neptune • This figure shows several of the largest known trans-Neptunian objects, now collectively called plutoids © 2017 Pearson Education, Inc Summary of Chapter • • • • • The outer solar system has large moons, 12 medium ones, and many smaller ones Titan has a thick atmosphere and may have flowing rivers of methane Triton has a fractured surface and a retrograde orbit Medium-sized moons of Saturn and Uranus are mostly rock and water ice Saturn’s rings are complex, and some are defined by shepherd moons © 2017 Pearson Education, Inc Summary of Chapter 8, cont • The Roche limit is the closest a moon can survive near a planet; inside this limit, rings form instead • • • Jupiter, Uranus, and Neptune all have faint ring systems Pluto has five moons: Charon, Nix, Styx, Kerberos, and Hydra Dwarf planets beyond Neptune (including Pluto) are now known as plutoids © 2017 Pearson Education, Inc ... in the solar system – – – It has many active volcanoes, some quite large Io can change surface features in a few weeks Io has no craters; they fill in too fast Io has the youngest surface of any... system—larger than Pluto and Mercury It has a history similar to Earth’s Moon, but with water ice instead of lunar rock © 2017 Pearson Education, Inc 8.1 The Galilean Moons of Jupiter • Callisto... many years to have an atmosphere thicker and denser than Earth’s; mostly nitrogen and argon • Titan’s cloudy atmosphere makes it impossible to see the surface; the picture at right was taken from