Astronomy 1010-H Planetary Astronomy Fall_2015 Day-34 Course Announcements • How is the sunset/sunrise observing going? • SW-chapter 9 due: Wed. Nov. 18 SW-chapter 10 due: Mon. Nov. 23 • • I will collect the L-T books on Monday, Nov. 23, though I will take them at any time now. • 1st Quarter Obs. (last one of semester): Thurs. Nov. 19 Reports Due: Monday Nov. 23 – AT CLASS TIME! • Jupiter and Saturn were known to the ancients. Uranus was too faint to be discerned from the other stars. Discovered in 1781 by Herschel by accident (at first thought it was a comet). Neptune was found because Uranus was straying from its predicted orbit. Gravity of Neptune was tugging on Uranus. Found in 1846 by Galle after being mathematically predicted by Le Verrier and Adams. Called giant planets because of their mass— from 14.5 Earth masses (Uranus) to 318 (Jupiter)—and also, their physical size. No solid surfaces: We just see the cloud layers in the atmospheres. More Giant Characteristics We see atmospheres (some very cloudy, some not), not surfaces. They are less dense than the terrestrial planets; in fact, Saturn would float in a large enough tub of water. Jupiter’s chemistry is like the Sun: mostly hydrogen and helium. Saturn has some more heavy elements, but is like Jupiter; Uranus and Neptune have much more heavy elements. Planetary diameters are found by observing how long it takes for a planet to pass over a star: stellar occultation. Planetary masses are found by observing the motions of a planet’s moons and effects of gravity. i_Clicker Question Jovian Planets: Jovian Transit Jovian Planets: Jupiter Formation All giants have rapid rotation and therefore different amounts of oblateness. They also have different obliquities. • Jupiter: 3°. • Uranus: 98°, which results in extreme seasons. i_Clicker Question Jovian Planets: Oblateness Strong dark and light bands. A long-lasting giant storm (Great Red Spot). Many smaller storms. Colors indicate complex chemistry. Saturn has a similar band structure to Jupiter, but less pronounced. It has violent storms and a feature similar to Earth’s jet stream.