Transcript Day-13
Astronomy 1010-H Planetary Astronomy Fall_2015 Day-13 Course Announcements • How is the sunset/sunrise observing going? • Dark Sky nights – Mon. 10/5 & Wed. 10/7 starting at 7:30pm – at the Observatory. • Total lunar eclipse: Sun.-Mon. 9/27-28 • • • Weather dependent, if clear, we’ll be setup at the observatory about sunset. Here’s the important information I will collect the L-T workbooks on Friday. • Make sure your name is in it. Kepler’s First Law: The orbit of a planet about the Sun is an ellipse with the Sun at one focus. Kepler’s Second Law: A line joining a planet and the Sun sweeps out equal areas in equal intervals of time. Lecture – Tutorial nd Kepler’s 2 Law: pg 21 Work with a partner! Read the instructions and questions carefully. Discuss the concepts and your answers with one another. Come to a consensus answer you both agree on. If you get stuck or are not sure of your answer, ask another group. If you get really stuck or don’t understand what the Lecture Tutorial is asking, ask one of us for help. According to Kepler’s second law, a planet with an orbit like Earth’s would: A. move faster when further from the Sun. B. move slower when closer to the Sun. C. experience a dramatic change in orbital speed from month to month. D. experience very little change in orbital speed over the course of the year. E. none of the above. Kepler’s second law says “a line joining a planet and the Sun sweeps out equal areas in equal amounts of time.” Which of the following statements means nearly the same thing? A. Planets move fastest when they are moving toward the Sun. B. Planets move equal distances throughout their orbit of the Sun. C. Planets move slowest when they are moving away from the Sun. D. Planets travel farther in a given time when they are closer to the Sun. E. Planets move the same speed at all points during their orbit of the Sun. THIRD LAW The size of the orbit determines the orbital period planets that orbit near the Sun orbit with shorter periods than planets that are far from the Sun p = ~ 12 years p = 1 year THIRD LAW The size of the orbit determines the orbital period planets that orbit near the Sun orbit with shorter periods than planets that are far from the Sun MASS DOES NOT MATTER Both have p = 1 year THIRD LAW The size of the orbit determines the orbital period planets that orbit near the Sun orbit with shorter periods than planets that are far from the Sun 3 a = AU 2 P years MATH TOOLS 3.2 Kepler’s third law in its simplest form utilizes nonstandard units—the periods are in years, while the distances are in AU. The relationship does not change if standard units are used. The equation is just more complicated. Consequences: • Distant planets take longer to orbit the Sun. • Distant planets travel at slower speeds.