Survey of Astronomy

Chapter 11 • JUPITER – Lord of the Planets Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 To discuss the Jovian Planets we must first talk about The Voyager program. The mission of Voyager 1 & 2 is to visit the Outer Solar System and beyond. Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 This is the Voyager 2 velocity profile showing the velocity flips at each planet. Our booster was barely able to reach Jupiter with- out gravity assist. With gravity assist we have left the Solar System Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 Jupiter can be imaged well from Earth, even with a small telescope Here: Jupiter with its Galilean moons Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 Earth Pioneer 1973 Voyager 1979 Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 • Mass: More than twice as much as all other planets put together. • Radius: 11.2 times Earth’s radius • Density: Only 1.3 x the density of water – cannot be rocky or metallic as terrestrial planets are • Rotation Rate: problematic, as Jupiter has no solid surface; different parts of atmosphere rotate at different rates. The solution came from magnetic field, whose rotation period is 9 hr, 55 min Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 Early images of Jupiter showed the Great Red Spot and Stripes. As our instruments improved many more details emerged. The spot became a giant storm and stripes became bands of rising and falling gases. Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 Great Red Spot has existed for at least 300 years, possibly much longer. It seems to be and inverted storm dipping to the planet rather that rising above it. The colors have changed over the years from brick red to light brown. The size has changed from 3x the size of the Earth to just over 2x. Voyager -Visible Survey of Astronomy Astro1010-lee.com Galileo-Infrared twlee2016@gmail.com

Chapter 11 The Atmosphere has bright zones and dark belts. Zones are rising warmer gasses from the interior, and are higher than belts. The Belts are cooler falling gases returning to be re-warmed. The many storms seen in the belts are due to turbulence caused by differential rotation in the atmosphere Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 The composition of the Atmosphere is mostly molecular hydrogen and helium with small amounts of methane, ammonia, and water vapor. The impurities seem to account for the colors, probably due to complex chemical interactions that we are still studying Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 No solid surface; take top of troposphere to be 0 km The lowest level of the atmosphere is the stripes. Telescopes can not see through it. Measurements by Galileo probe show high wind speeds even at great depth – probably due to heating from inside the planet, not from Sun Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 Great Red Spot has existed for at least 400 years, possibly much longer Color and energy source still not fully understood Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 Lightning-like flashes have been seen; also shorter-lived rotating storms One example: Brown Oval, really a large gap in clouds Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 We find that Jupiter radiates more energy than it receives from the Sun: Core is still cooling off from heating during gravitational compression. Could Jupiter have been a star? No; it is far too cool and too small for that. It would need to be about 80 times more massive to be even a very faint star Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 No direct information is available about Jupiter’s interior, but its main components, hydrogen and helium, are quite well understood. The central portion is a rocky core. Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 Jupiter is surrounded by belts of charged particles, much like the Van Allen belts but vastly larger Magnetosphere is 30 million km across Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 Intrinsic field strength is 20,000 times that of Earth Magnetosphere can extend beyond the orbit of Saturn Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 • More than 60 moons have now been found orbiting Jupiter, but most are very small. • The four largest are the Galilean moons, so called because they were first observed by Galileo: • Io, Europa, Ganymede, Callisto • Galilean moons have similarities to terrestrial planets; orbits have low eccentricity, largest is somewhat larger than Mercury, and density decreases as distance from Jupiter increases Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 The Small moons move in mostly eccentric orbits far from Jupiter. Here, the orbits of the Galilean moons can be seen in the center near the planet. Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 These are the Galilean moons. Each is unique. Each is interesting. Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 The Galileo Probe has given us a very good feel for their interiors Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 Io is the most dense of Jupiter’s moons, and the most geologically active object in the solar system. It has many active volcanoes, some quite large. It can change surface features in a few weeks There are no impact craters; they fill in too fast – Io has the youngest surface of any solar system object. The many colors come from sulfur at different temperatures Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 The vulcanism on Io is due to tidal forces. Io is very close to Jupiter in a rather eccentric orbit, and also experiences gravitational forces from Europa and Ganymede. The tidal forces are huge and provide the energy for the Volcanoes. This image of Io is the discovery image for the volcanos Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 Volcanic eruptions also eject charged particles; these interact with Jupiter’s magnetosphere and form a plasma torus Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 The moon Europa has no impact craters, The surface is water ice, likely with liquid water below Tidal forces stress and crack the ice allowing liquid water to flow out keeping surface glass smooth Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 Ganymede is the largest moon in the solar system – larger than the planet Mercury Impact history similar to Earth’s Moon, but water ice and dirt instead of lunar rock Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 Surface areas of Ganymede once thought to be cratered and flat turn out to have structures. These may be due to a form of plate tectonics Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 Calisto is similar to Ganymede except there is no evidence of plate activity. Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 One of the big surprises of the Voyager program was the discovery of a ring around Jupiter. This is the discovery image. Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 These four moonlets are associated with Jupiter’s ring. The two tiniest, Metis and Adastria are embedded in the ring and seem to be shattering to feed the ring. The other two, Amalthea and Thebe, are “Shepherd” moons. Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 This image made by the Galileo spacecraft shows more details. Especially evident are the sharp outer edge and the diffuse inner edge of the ring and the detail within the rings are explained by the presence of the moonlets. Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 End of Chapter 11 Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Chapter 11 Survey of Astronomy Astro1010-lee.com twlee2016@gmail.com

Survey of Astronomy