NAME (PRINT): (Family Name) (Given Name) STUDENT NO: SIGNATURE: UNIVERSITY OF TORONTO MISSISSAUGA APRIL 2020 FINAL EXAMINATION AST201H5S Stars and Galaxies J. B. Lester Duration – 3 hours Aids allowed: ruler The University of Toronto Mississauga and you, as a student, share a commitment to academic integrity. You are reminded that you may be charged with an academic offence for possessing any unauthorized aids during the writing of your final examination. Clear, sealable plastic bags have been provided for all electronic devices with storage, including, but not limited to, cell phones, smart watches, SMART devices, tablets, laptops and unau- thorized calculators. Turn off all devices, seal them in the bag provided, and place the bag under your desk for the duration of the final examination. You will not be allowed to touch the bag or its contents until the final examination is over. If, during the final examination, any of these items are found on your person or in the area of your desk, other than in the clear, sealable plastic bag, you may be charged with an academic offence. A typical penalty for an academic offence may cause you to fail this course. Please note, once this final examination has begun, you CANNOT re-write it. Notes to students: 1. Enter your name and student number on each page of this examination. 2. The mark value of each question is indicated in the parentheses to the left of the question number. 3. The total marks for this exam equals 118. 4. There are a total of 17 pages in this exam. All 17 pages must be handed in at the end of the exam. continued on page 2 AST201H5S April 2020 Final Examination Page 2 of 17 NAME (PRINT): (Family Name) (Given Name) STUDENT NO: SIGNATURE: The first part of this final examination has 8 multiple-choice ques- tions, each worth 1 mark. Circle the letter of the MOST correct answer for each multiple-choice question. 1. Where are the youngest stars in the Milky Way located?(1 mark) (A) In the Milky Way’s bulge. (B) In the Milky Way’s halo. (C) Near the Milky Way’s central black hole. (D) In the Milky Way’s spiral arms. (E) In the Milky Way’s disk. /1 Mark 2. Where do stars in the Milky Way’s disk have the slowest orbit speed?(1 mark) (A) At the outer edge of the Milky Way’s disk. (B) Between the Milky Way’s spiral arms. (C) Near the Milky Way’s central black hole. (D) In the Milky Way’s spiral arms. (E) The orbit speed is almost constant. /1 Mark 3. What type of galaxy has the largest fraction of young stars?(1 mark) (A) Irregular galaxies. (B) Regular spiral galaxies. (C) Barred spiral galaxies. (D) Elliptical galaxies. (E) All galaxies have the same fraction of young stars. /1 Mark continued on page 3 AST201H5S April 2020 Final Examination Page 3 of 17 NAME (PRINT): (Family Name) (Given Name) STUDENT NO: SIGNATURE: 4. How do we know that a quasar is smaller than our solar system?(1 mark) (A) A quasar has a very fast rotation speed. (B) A quasar has a huge redshift. (C) A quasar varies its brightness in a few days. (D) A quasar emits radio waves. (E) A quasar is 1000 times brighter than the Milky Way. /1 Mark 5. Suppose you lived on a planet orbiting a star in a galaxy 5 billion light-(1 mark) years from the Milky Way. What value would you measure for the Hubble constant? (A) The Hubble constant would be 5 times larger than the value we measure. (B) The Hubble constant would be the same as the value we measure. (C) The Hubble constant would be 1/5 the value we measure. (D) The Hubble constant would be 0. (E) The Hubble constant’s value would depend on the type of galaxy. /1 Mark 6. Why are all the galaxies we observe less than 14 billion light-years from the(1 mark) Milky Way? (A) The Cosmic Microwave Background has a temperature of 2.7 K. (B) The Milky Way formed 13 billion years ago. (C) The solar system formed 5 billion years ago. (D) The age of the Universe is 14 billion years. (E) The Universe is “flat”. /1 Mark continued on page 4 AST201H5S April 2020 Final Examination Page 4 of 17 NAME (PRINT): (Family Name) (Given Name) STUDENT NO: SIGNATURE: 7. A star hotter than our Sun has a larger “habitable zone” than our Sun. Why(1 mark) do astronomers think these stars are unlikely to have life on their planets? (A) Hotter stars rotate more rapidly than our Sun. (B) Hotter stars cause their planets to orbit more rapidly than our Sun. (C) Hotter stars have fewer planets than our solar system. (D) Hotter stars are less common than stars like our Sun. (E) Hotter stars have shorter lifetimes than our Sun. /1 Mark 8. Some astronomers think life might exist on a moon of Jupiter. What is the(1 mark) justification for this idea? (A) A moon of Jupiter has liquid water. (B) A moon of Jupiter is larger than the planet Mercury. (C) A moon of Jupiter has very few collisions with other bodies. (D) A moon of Jupiter has a short orbit period. (E) A moon of Jupiter has many companion moons. /1 Mark continued on page 5 AST201H5S April 2020 Final Examination Page 5 of 17 NAME (PRINT): (Family Name) (Given Name) STUDENT NO: SIGNATURE: The second part of the final examination consists of 22 short- answer questions. • Each question is worth five (5) marks, but you are NOT required to provide five separate points in your answer. • Explain the key idea(s) for each question. • You can use point form in your answers. • You can sketch diagrams as part of your answer. • Partial marks will be given for partial explanations. 9. Explain how astronomers discovered the Sun is NOT at the centre of the(5 marks) Milky Way. /5 Marks continued on page 6 AST201H5S April 2020 Final Examination Page 6 of 17 NAME (PRINT): (Family Name) (Given Name) STUDENT NO: SIGNATURE: 10. The space between the stars looks empty, but it contains a very thin gas(5 marks) of atoms and molecules and also “dust” particles. Although a dust particle is microscopically tiny, it contains many atoms and molecules. Explain how the tiny dust particles affect the study of the Milky Way. /5 Marks 11. Explain the method astronomers used to discover that as much as 95% of(5 marks) the matter in the Milky Way is invisible “dark matter”. /5 Marks continued on page 7 AST201H5S April 2020 Final Examination Page 7 of 17 NAME (PRINT): (Family Name) (Given Name) STUDENT NO: SIGNATURE: 12. Explain how astronomers proved there are galaxies outside the Milky Way.(5 marks) /5 Marks 13. Explain how the Doppler effect can be used to measure the distance of a(5 marks) galaxy from the Milky Way. /5 Marks continued on page 8 AST201H5S April 2020 Final Examination Page 8 of 17 NAME (PRINT): (Family Name) (Given Name) STUDENT NO: SIGNATURE: 14. Explain what a “MACHO” is, and how astronomers are trying to detect(5 marks) them. /5 Marks 15. Explain how the Hubble law leads to the Big Bang Theory.(5 marks) /5 Marks continued on page 9 AST201H5S April 2020 Final Examination Page 9 of 17 NAME (PRINT): (Family Name) (Given Name) STUDENT NO: SIGNATURE: 16. Explain how the Big Bang Theory was confirmed.(5 marks) /5 Marks 17. Explain why at least 24% of the mass of every star is helium.(5 marks) /5 Marks continued on page 10 AST201H5S April 2020 Final Examination Page 10 of 17 NAME (PRINT): (Family Name) (Given Name) STUDENT NO: SIGNATURE: 18. Describe the Miller-Urey experiment and explain why it was important.(5 marks) /5 Marks 19. Astronomers have estimated that our Milky Way might have a billion(5 marks) planets like Earth capable of having life. Explain how this estimate was made. /5 Marks continued on page 11 AST201H5S April 2020 Final Examination Page 11 of 17 NAME (PRINT): (Family Name) (Given Name) STUDENT NO: SIGNATURE: 20. Explain why astronomers are searching for signals from other intelligent(5 marks) civilizations in the “waterhole”, with a wavelength of about 20 cm. /5 Marks 21. Hydrogen atoms are 90% of the atoms in the Universe. Explain which(5 marks) fundamental force is essential for hydrogen atoms to exist. /5 Marks continued on page 12 AST201H5S April 2020 Final Examination Page 12 of 17 NAME (PRINT): (Family Name) (Given Name) STUDENT NO: SIGNATURE: 22. The following diagram shows two images of the Sun. Explain what we(5 marks) learn from these observations. /5 Marks continued on page 13 AST201H5S April 2020 Final Examination Page 13 of 17 NAME (PRINT): (Family Name) (Given Name) STUDENT NO: SIGNATURE: 23. Explain how you are obeying Newton’s 1st law of motion as you answer(5 marks) this question. /5 Marks 24. Explain how Einstein’s theory of general relativity is a new theory of(5 marks) gravity. /5 Marks continued on page 14 AST201H5S April 2020 Final Examination Page 14 of 17 NAME (PRINT): (Family Name) (Given Name) STUDENT NO: SIGNATURE: 25. The following diagram shows a plot of the Sun’s spectrum observed from(5 marks) Earth. Explain how we derive the temperature of the Sun’s surface from this plot. /5 Marks continued on page 15 AST201H5S April 2020 Final Examination Page 15 of 17 NAME (PRINT): (Family Name) (Given Name) STUDENT NO: SIGNATURE: 26. The largest existing telescope for visible light has a diameter of 10.4 metres.(5 marks) The largest existing telescope for radio waves has a diameter of 500 metres. Explain why the diameter of the radio telescope needs to be so much larger than the diameter of the telescope for visible light. /5 Marks 27. Explain the concept of hydrostatic equilibrium. Why is hydrostatic equi-(5 marks) librium important for understanding the structure of the Sun? /5 Marks continued on page 16 AST201H5S April 2020 Final Examination Page 16 of 17 NAME (PRINT): (Family Name) (Given Name) STUDENT NO: SIGNATURE: 28. Explain what is learned from the following images.(5 marks) /5 Marks continued on page 17 AST201H5S April 2020 Final Examination Page 17 of 17 NAME (PRINT): (Family Name) (Given Name) STUDENT NO: SIGNATURE: 29. Explain how the oxygen we inhale with each breath was created.(5 marks) /5 Marks 30. Astronomers have discovered a pulsar that rotates more than 700 times(5 marks) each second. Explain what causes the pulsar to rotate so rapidly. /5 Marks Total Marks = 118 End of Exam
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