# Ch7 - Assignment Chapter 7 Class Astronomy I Date September...

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Assignment: Chapter 7 Class: Astronomy I Date: September 17 th , 2007 Review Questions 1. Do all the planets orbit the Sun in the same direction? Are all of the orbits circular? If one observes the solar system from a point several astronomical units above the Earth’s north pole, one would be able to see that the planets do orbit in circular (elliptical) paths in the same direction. 2. What are the characteristics of a terrestrial planet? Terrestrial planets are the four small inner planets that resemble the Earth. They have hard, rocky surfaces with mountains, craters, valleys, and volcanoes like the Earth. 3. What are the characteristics of a Jovian planet? The four large outer planets which include Jupiter, Saturn, Uranus and Neptune are called Jovian planets because they resemble Jupiter. These planets are mostly made of gas or liquid, and the visible surface features are actually cloud formations in the planet’s atmosphere. 4. What is meant by the average density of a planet? What does the average density of a planet tell us? The average density of a planet is its mass divided by the volume in kilograms per cubic meter. The density depends in part on that substance’s chemical composition. It basically tells us how full the planet’s area is in relation to its size. 5. In What ways are the largest satellites similar to the terrestrial planets? In what ways are they different? Which satellites are the largest? Satellites with big average densities indicate that they are made primarily of rocky materials like the terrestrial planets. By contrast, the average densities of Ganymede, Callisto, Titan, and Triton are all relatively low. Planetary scientists conclude that these planets contain water ice that is less dense than rock. The biggest satellite is Ganymede with a diameter of 5268 km. 6. The absorption lines in the spectrum of a planet or satellite do not necessarily indicate the composition of the planet or satellite’s atmosphere. Why not? If a planet has an atmosphere, the sunlight reflected from the planet must have passed through its atmosphere. During this passage, some of the wavelengths of sunlight will have been absorbed. In other words, the absorption line changes as it passes through the Sun’s sphere and the Earth’s sphere before reaching the telescope. 7. What are the differences in chemical composition between the terrestrial and Jovian planets? While Jovian planets are composed of gases like hydrogen, helium, ammonia, and

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Ch7 - Assignment Chapter 7 Class Astronomy I Date September...

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