AST201_midterm2_solutions

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Department
Astronomy & Astrophysics
Course
AST201H1
Professor
Michael Reid
Semester
Winter

Description
UNIVERSITY OFTORONTO ASTRONOMY 201H1 MIDTERM TEST #2 THURSDAY, MARCH 17, 2011 DURATION: 45 MINUTES NO AIDSALLOWED UTORID: _________________________________ CIRCLE THE TUTORIALSECTION YOUATTEND: Monday Tuesday Wednesday 10:00 0101 -- Santiago -- 0601 -- Ivana 0602 --Alana 1101 -- Ivana 1102 -- Yevgeni 11:00 0201 -- Santiago 0202 --Alana 0701 –Adam 0702 -- Santiago 1201 --Alana 1202 -- Yevgeni 12:00 0301 -- Sergei 0302 -- Greg 0801 -- Natalie0802 -- Jeffrey 1301 -- Sergei 1302 -- Natalie 13:00 0401 -- Wayne 0402 -- Greg 0901 --Adam 0902 -- Jeffrey 1401 -- Sergei 1402 -- Yevgeni 14:00 0501 -- Wayne 0502 -- Jeffrey 1001 --Adam 1002 -- Emma 1501 -- Emma 1502 -- Wayne 1601 – Emma 1602 – Natalie - - 15:00 Instructions: 1. ON THIS PAGE: Fill in your UTorID (e.g. smithm1) and circle your tutorial section. 2. ON THE NEXT PAGE: Fill in your name (as it appears on ROSI), your student number, and your UTorID (e.g. smithm1). 3. ON THE SCANTRON CARD: Fill in your last name, first initial, and student number in the spaces given and, using pencil, darkly shade in the corresponding bubbles. Then sign the card. 4. For each multiple choice question, mark your answer in pencil on the Scantron card by darkly shading the appropriate bubble. All answers to multiple choice questions must be transferred to the Scantron card. Under no circumstances will answers to multiple choice questions written on this paper be accepted. 5. Answer short answer questions in the spaces provided. Answers written in pencil will not be re- marked. 6. Mark values are indicated with each question. 7. Make sure that your midterm has 10 pages. AST 201 MIDTERM 2, WINTER 2011 PAGE 1 OF 10 NAME: __________________________________ UTORID: ________________________________ STUDENT NUMBER: _____________________ Question Marks A1-A20 (MC) /20 B1 /2 B2 /4 B3 /3 B4 /3 B5 /3 Total for Part B /35 AST 201 MIDTERM 2, WINTER 2011 PAGE 2 OF 10 PARTA: Multiple choice questions. CIRCLE THE MOST CORRECTANSWER (1 mark each) 1. Every second, a solar panel on the International Space Station, in orbit around Earth, absorbs a certain amount of solar energy, E, each second. Approximately how much energy would the same solar panel absorb from the Sun each second if it were instead in orbit around Jupiter, at about 5AU from the Sun? (a) E/25 * (b) E/5 (c) E (d) 5E (e) 25E 2. Consider the image on the right, which shows many stars. Which of the circled stars has the highest luminosity? In each case, consider the “circled star” to be the brightest one within the circle. (a) star A (b) star B (c) star C (d) star D (e) We can't say for sure * 3. Even with telescopes, we don't see many visual binary star systems. Why not? (a) Most stars are not in binaries. (b) Visual binaries are usually obscured by clouds of dust and gas. (c) Most visual binaries are oriented with their orbital planes along our line of sight. (d) The stars in most visual binaries are too close together for us to tell them apart. * (e) We have not spent enough time looking for visual binaries. 4. Consider the following set of stellar spectra. Which one is most likely to belong to a star with spectral class K? (*ANSWER: B*) AST 201 MIDTERM 2, WINTER 2011 PAGE 3 OF 10 5. The visible-light spectrum of a star of spectral type O shows much weaker hydrogen absorption lines than a star of spectral typeA. What property of the outer layers of these stars explains this observation? (a) Compared to anAstar, an O star is cooler. (b) Compared to anAstar, an O star is has less hydrogen, so there is less of it to do the absorbing. (c) Compared to anAstar, an O star has more helium, which dominates the absorption features. (d) Compared to anAstar, an O star is longer-lived, so it has to use up its hydrogen more slowly. (e) Compared to anAstar, a larger fraction of the hydrogen in an O star is ionized. * 6. Two stars,Aand B, have the same mass but starAhas a higher luminosity. Which one will spend more time on the main sequence? (a) star A (b) star B * (c) need more information 7. If the Picard star cluster has a main-sequence turn-off at spectral class B while the Kirk star cluster has a main-sequence turn-off at spectral class F, which cluster is older? (a) need more information (b) Kirk * (c) Picard 8. If you want to find areas of the Galaxy in which there are lots of young stars, you should look for groups of stars of spectral class: (a) O * (b) F (c) G (d) K (e) M 9. Which of the following phrases could be used to help you remember the stellar spectral classes in order from hottest to coolest stellar surface temperature? (a) Oh My! AFine Giraffe Baking Knishes! (b) Many Knowledgeable Grandfathers ForgiveAncient Battles Openly (c) BeAFine Guy, Kiss My Ocelot (d) Only Foolish Girls Kiss ManyAwful Boys (e) Only BunglingAstronomers Forget Generally Known Mnemonics * (f) Overly FunnyAstronomers Boost Midterm Grades Kreatively AST 201 MIDTERM 2, WINTER 2011 PAGE 4 OF 10 10. Consider the image on the right (identical to one shown in colour in class), which shows a star in the process of forming. What is happening in this image? (a) Material is flowing onto the protostar through the disk (Y), and flowing away from the protostar through the jet (X). * (b) Material is flowing onto the protostar through the jet (X), and flowing away from the protostar through the disk (Y). (c) Material is flowing from the nebula (Y), onto the star through the disk (X). (d) Material is flowing from the nebula, through the jet (X), onto the disk (Y). 11. Over the course of its MAIN-SEQUENCE lifetime, how will the Sun move through the H-R diagram? (a) It will move far up the main sequence. (b) It will move off the main sequence toward the red side of the diagram. (c) It will remain nearly stationary in the H-R diagram. * (d) It will move far down the main sequence. (e) It will move off the main sequence toward the blue side of the diagram 12. Normally, a dying star is prevented from collapsing completely by electron degeneracy pressure. Nevertheless, some massive stars manage to overcome this degeneracy pressure and collapse to form neutron stars or black holes. How can they overcome the electron degeneracy pressure? (a) The gravity of the stars is strong enough to tear the electrons apart. (b) They combine the electrons with prot
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