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Astronomy A BEGINNER’S GUIDE TO THE UNIVERSE EIGHTH EDITION CHAPTER 7 The Jovian Planets Lecture Presentation © 2017 Pearson Education, Inc. Chapter 7 The Jovian Planets © 2017 Pearson Education, Inc. Units of Chapter 7 • • • • • • • Observations of Jupiter and Saturn The Discoveries of Uranus and Neptune Bulk Properties of the Jovian Planets Jupiter’s Atmosphere Atmospheres of the Outer Jovian Worlds Jovian Interiors Summary of Chapter 7 © 2017 Pearson Education, Inc. 7.1 Observations of Jupiter and Saturn • Jupiter can be imaged well from Earth, even with a small telescope. • Here: Jupiter with its Galilean moons © 2017 Pearson Education, Inc. 7.1 Observations of Jupiter and Saturn • True-color image of Jupiter © 2017 Pearson Education, Inc. 7.1 Observations of Jupiter and Saturn • Natural-color image of Saturn © 2017 Pearson Education, Inc. 7.1 Observations of Jupiter and Saturn • Cassini image of Jupiter, true color © 2017 Pearson Education, Inc. 7.2 The Discoveries of Uranus and Neptune • Uranus, in natural color • Note the absence of features. © 2017 Pearson Education, Inc. 7.2 The Discoveries of Uranus and Neptune • Neptune in natural color © 2017 Pearson Education, Inc. 7.3 Bulk Properties of the Jovian Planets • The Jovian planets are large and much less dense than the terrestrial planets; Saturn is less dense than water! © 2017 Pearson Education, Inc. 7.3 Bulk Properties of the Jovian Planets • Jovian planets, compared to Earth © 2017 Pearson Education, Inc. 7.3 Bulk Properties of the Jovian Planets • Peculiarity of Uranus: Axis of rotation lies almost in the plane of its orbit. Seasonal variations are extreme. © 2017 Pearson Education, Inc. 7.4 Jupiter’s Atmosphere • Atmosphere has bright zones and dark belts. • Zones are cooler and are higher than belts. • Stable flow underlies zones and bands, called zonal flow. • Simplified model: © 2017 Pearson Education, Inc. 7.4 Jupiter’s Atmosphere • Jupiter has no solid surface; take the top of troposphere to be 0 km. • Lowest cloud layer cannot be seen by optical telescopes. • Measurements by Galileo probe show high wind speeds even at great depth—probably due to heating from planet, not from Sun. © 2017 Pearson Education, Inc. 7.4 Jupiter’s Atmosphere • The Galileo probe descended into Jupiter’s atmosphere and returned valuable data. The arrow indicates its entry point. © 2017 Pearson Education, Inc. 7.4 Jupiter’s Atmosphere • Major visible features: – Bands of clouds and the Great Red Spot © 2017 Pearson Education, Inc. 7.4 Jupiter’s Atmosphere • Hubble Space Telescope (HST) observations of the Great Red Spot: Merging spots are seen in the top sequence. Lower sequence shows the shrinking Great Red Spot between 1995 and 2014. © 2017 Pearson Education, Inc. 7.5 Atmospheres of the Outer Jovian Worlds • The atmosphere of Saturn is similar to that of Jupiter, except that Saturn is somewhat colder, its atmosphere is thicker, and its bands are fainter. © 2017 Pearson Education, Inc. 7.5 Atmospheres of the Outer Jovian Worlds • Saturn’s atmosphere is similar to Jupiter’s, except pressure is lower. • It has three cloud layers. • Cloud layers are thicker than Jupiter’s; we see only the top layer. © 2017 Pearson Education, Inc. 7.5 Atmospheres of the Outer Jovian Worlds • Saturn also has large storms. This 2011 storm generated its own band, as seen in this sequence of images from Cassini. © 2017 Pearson Education, Inc. 7.5 Atmospheres of the Outer Jovian Worlds • This storm was observed by the Cassini spacecraft in 2011 in visible light. • The right-hand image shows an infrared image taken after the band had faded in visible light. © 2017 Pearson Education, Inc. 7.5 The Atmospheres of the Outer Jovian Worlds • Saturn, like Earth and Venus, has enormous polar vortices that resemble huge storm systems. The southern vortex is shown in the top image, northern vortex on the bottom. © 2017 Pearson Education, Inc. 7.5 The Atmospheres of the Outer Jovian Worlds • Rotation of Uranus can be measured by watching storms. © 2017 Pearson Education, Inc. 7.5 The Atmospheres of the Outer Jovian Worlds • Neptune has storm systems similar to those on Jupiter, but fewer. The large storm system at the top has disappeared in recent years. © 2017 Pearson Education, Inc. 7.6 Jovian Interiors • No direct information is available about Jupiter’s interior, but its main components, hydrogen and helium, are quite well understood. The central portion is thought to be a rocky core. © 2017 Pearson Education, Inc. 7.6 Jovian Interiors • Interior structure of Uranus and Neptune, compared to that of Jupiter and Saturn © 2017 Pearson Education, Inc. 7.6 Jovian Interiors • Jupiter’s magnetosphere: – Intrinsic field strength is 20,000 times that of Earth. – Magnetosphere can extend beyond the orbit of Saturn. © 2017 Pearson Education, Inc. 7.6 Jovian Interiors • Aurorae are seen on Jupiter and have the same cause as those on Earth—the interaction of solar wind particles with the magnetosphere. © 2017 Pearson Education, Inc. 7.6 Jovian Interiors • Uranus and Neptune both have substantial magnetic fields, but at a large angle to their rotation axes. – The rectangle within each planet shows a bar magnet that would produce a similar field. Note that both Uranus’s and Neptune’s are significantly off center. © 2017 Pearson Education, Inc. Summary of Chapter 7 • Jupiter and Saturn were known to the ancients; Uranus was discovered by chance, and Neptune was predicted from anomalies in the orbit of Uranus. • Jovian planets are large but not dense; they are fluid and display differential rotation. • Cloud layers have light zones and dark bands; wind pattern, called zonal flow, is stable. © 2017 Pearson Education, Inc. Summary of Chapter 7, cont. • Storms appear with regularity; the Great Red Spot of Jupiter has lasted for hundreds of years (that we know of). • Due to conductive interiors and rapid rotation, Jovian planets have large magnetic fields. • Jupiter, Saturn, and Neptune radiate more energy than they receive from the Sun. © 2017 Pearson Education, Inc.