Queens Astro Section 1 - Fall 2012 Signed in as Jonathan Leb Help Close HW #7 - The Sun & Surveying the Stars (Chapters 10 & 11) Due: 11:58pm on Sunday, November 18, 2012 Note: You will receive no credit for late submissions. To learn more, read your instructor's Grading Policy Chapter 10: Reading Quiz Part A According to modern science, approximately how old is the Sun? ANSWER: Part B The Sun will exhaust its nuclear fuel in about . ANSWER: 10,000 years 25 million years 4 1/2 billion years 400 million years. Correct The Sun is the same age as the rest of our solar system, which from earlier chapters is 4.5 billion years. 50 billion years 5 million years 5 billion years 5000 AD Study Section 10.1 of The Essential Cosmic Perspective in your textbook. Study Section 10.1 of The Essential Cosmic Perspective in your textbook. HW #7 - The Sun & Surveying the Stars (Chapters 10 & 11) 12/21/12 12:20 AM Page 2 of 63 Part C Which of the following correctly describes how the process of gravitational contraction can make a star hot? Correct The Sun's total life time is about 10 billion years, and the Sun is only about halfway through this lifetime at present. HW #7 - The Sun & Surveying the Stars (Chapters 10 & 11) 12/21/12 12:20 AM Page 3 of 63 ANSWER: Part D What two physical processes balance each other to create the condition known as gravitational equilibrium in stars? ANSWER: Part E The source of energy that keeps the Sun shining today is . ANSWER: Study Section 10.1 of The Essential Cosmic Perspective in your textbook. Correct This process is called gravitational contraction because gravity is what makes the star contract. the strong force and the weak force gravitational force and outward pressure the strong force and the electromagnetic force gravitational force and surface tension Correct This dynamic is important for understanding stellar structure and stellar evolution. chemical reactions nuclear fission gravitational contraction nuclear fusion Gravitational contraction involves the generation of heat by chemical reactions, much like the burning of coal. Heat is generated when gravity contracts, because gravity is an inverse square law force. When a star contracts in size, gravitational potential energy is converted to thermal energy. Gravitational contraction involves nuclear fusion, which generates a lot of heat. Study Section 10.1 of The Essential Cosmic Perspective in your textbook. Study Section 10.1 of The Essential Cosmic Perspective in your textbook. Correct The Sun shines by fusing hydrogen into helium, a process in which a small amount of the mass is converted into energy.