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HOMEWORK #17 My Star name is _______________ (due at the start of class on Thursday, March 23) (copyright D. McCarthy) GOALS for this assignment: 1. To review and reinforce the concepts of “stellar evolution.” 2. To understand some real evidence for the existence of “neutron stars” and “black holes.” TO RECEIVE FULL CREDIT, you must follow all these instructions carefully. 1. Write your Star name at the top of your homework. 2. Staple multiple pages; otherwise you will lose 5 points! 3. Follow all the week’s Daily Skills, both numerical and communication. 4. All sentence responses must be typewritten and in complete sentences. You may handwrite any arithmetic. Use good English grammar. 5. To receive any credit for numerical problems, you must show how you derived your answer by writing down all the logical steps that led you to it. 6. If you work more than two hours on this assignment, you should stop, record your work here, and contact Dr. McCarthy and Ms. Huang for help. You can also get help during Wednesday’s study session (2-4 pm), Tuesday’s office hours (noon-2 pm), or you can make an appointment. Part I. Mastering Astronomy #1. Login to your account on Mastering Astronomy and complete the assignment called “Homework #17 (Part I): Black Holes.” Part II. Good review for Exam #2: Reading and video #2. The following 4-minute video and associated article are good summaries about neutron stars and pulsars: https://www.youtube.com/watch?v=EYdnZ-Rf0rc http://www.universetoday.com/25376/pulsars/ [The video and article state that stars with masses between 1.4 and 3.2 MSun can become neutron stars. Technically, that range refers to the mass leftover in a remnant of a supernova explosion. In class we have said that stars that were born with more than 8 MSun will explode as supernovae leaving behind a remnant that can become either a neutron star or a black hole depending on the remaining mass of that remnant.] #3. The following article describes the Hulse-Taylor binary pulsar we discussed in class: http://www.astro.cornell.edu/academics/courses/astro201/psr1913.htm Part III. Answer these brief questions (taken from Bennett’s textbook) #4. Are all neutron stars also pulsars? Explain. Does It Make Sense? Decide whether each of the following statements makes sense (is clearly true) or does not make sense (is clearly false). Explain your reasoning thoroughly. #5. “The white dwarf at the center of the Helix Nebula has a mass three times the mass of our Sun.” #6. “The pulsation period of a pulsar appears to speed up if the pulsar is moving towards us.” #7. “We can detect black holes with X-ray telescopes because matter falling into a black hole emits X-rays after it smashes into the event horizon.” Optional short essay answer (20 points of extra-credit): #8. Discuss the evidence that gravitational waves are produced by neutron stars in binary systems. Include a description of the last two Figures in reading #3 about the binary pulsar.