Brock University Test 1, February, 2017 Number of pages: 9 Course: ASTR 1P02 Number of Students: 480 Date of Examination: February 6, 2017 Number of hours: 50 min Time of Examination: 18:00 18:50 Instructor: B.Mitrović 1. A 0.03 solar mass protostar will become (a) a black dwarf. (b) a red dwarf. (c) a brown dwarf. 2. A 0.6 solar mass protostar will become (a) a brown dwarf. (b) a black dwarf. (c) a red dwarf. 3. The Sun will end up as (a) black hole. (b) brown dwarf. (c) red dwarf. (d) white dwarf. 4. The larger the mass of a star, the longer is the time it spends in the protostar stage. 5. A reddish nebula is (a) the giant molecular clouds. (b) the reflection nebulae. (c) the emission nebulae. (d) the planetary nebulae. 1
Course: ASTR1P02 Date: February 6, 2017 page 2 of 9 pages 6. The giant molecular clouds are given the name molecular because they contain the molecules of. (a) ethyl alcohol (b) helium (c) hydrogen (d) amino acids 7. Which of these stars has the shortest main sequence life? (a) 25 solar mass star. (b) 10 solar mass star. (c) 5 solar mass star. (d) 2 solar mass star. 8. Which light is scattered more efficiently by gas and dust? (a) Blue light. (b) Red light. 9. The protostars could be observed in the part of the spectrum. (a) infrared (IR) (b) ultraviolet (UV) (c) X-ray (d) gamma-ray 10. Which of these main sequence stars fuses hydrogen to helium via proton-proton chain? (a) Stars with masses less than 0.08 solar mass. (b) Stars with masses from 0.5 to 2 solar mass. (c) Stars with masses greater than 2 solar mass. (d) All stars fuse hydrogen into helium via proton-proton chain regardless of their mass. 11. Just after the Sun became a main sequence star its luminosity (a) was greater than it is today because it had more hydrogen in its fusion core. (b) was the same as it is today because all main sequence stars are in hydrostatic equilibrium. (c) was less than it is today because the temperature of the fusing core was lower (10 million K) than it is today (15 million K). 2
Course: ASTR1P02 Date: February 6, 2017 page 3 of 9 pages 12. Once the Sun converts all of the hydrogen in its core to helium it will become (a) a red giant. (b) a pulsating yellow giant. 13. The helium core of a star heats up as a result of (a) pressure created by degenerate electrons. (b) gravitational contraction. (c) heat produced in hydrogen fusing shell around the helium core. 14. A white dwarf emits light because (a) helium nuclei are fusing into carbon with a release of energy. (b) degenerate electrons could drop into the lower energy levels and emit photons in the process. (c) carbon nuclei could drop into the lower energy levels and emit photons in the process. 15. Which of these fusion reactions requires the highest core temperature? (a) Fusion of hydrogen to helium. (b) Fusion oh helium to carbon. (c) Fusion of carbon to neon. (d) Fusion of silicon to iron. 16. Which of these fusion reactions in the core takes the least amount of time? (a) Fusion of hydrogen to helium. (b) Fusion oh helium to carbon. (c) Fusion of carbon to neon. (d) Fusion of silicon to iron. 17. The pressure created by degenerate electrons increases with (a) increasing temperature. (b) decreasing temperature. (c) increasing electron density. 3
Course: ASTR1P02 Date: February 6, 2017 page 4 of 9 pages 18. Which of these nuclei has the highest binding energy per nucleon (proton or neutron)? (a) Helium. (b) Carbon. (c) Silicon. (d) Iron. (e) Gold. 19. The nuclei of gold were formed (a) by fission of uranium formed in the fusing core of a high mass star. (b) by the nucleosynthesis in the fusing core of a high mass star. (c) during a supernova as the shock wave and the thermal neutrinos supplied the energy. 20. Which of these fusion reactions releases the largest amount of energy per reaction? (a) Fusion of hydrogen to helium. (b) Fusion oh helium to carbon. (c) Fusion of carbon to neon. (d) Fusion of silicon to iron. 21. Which of these white dwarfs has the largest radius? (a) 0.8 solar mass white dwarf. (b) 0.9 solar mass white dwarf. (c) 1 solar mass white dwarf. (d) 1.3 solar mass white dwarf. 22. The density of a typical neutron star is about (a) 10 3 kg/cm 3. (b) 10 11 kg/cm 3. 23. A white dwarf is composed of (a) carbon nuclei, some oxygen nuclei, and degenerate electrons. (b) iron nuclei and degenerate electrons. (c) helium nuclei and degenerate electrons. 4
Course: ASTR1P02 Date: February 6, 2017 page 5 of 9 pages 24. Suppose you read in a paper that a white dwarf of five solar masses has been detected. Having taken the Astronomy course you know that the claim cannot be true because it violates (a) the conservation of energy. (b) the conservation of angular momentum. (c) the Newton s law of gravity. (d) the Chandrasekhar limit. 25. Which of these main sequence stars fuses hydrogen to helium via CNO-cycle? (a) Stars with masses less than 0.08 solar mass. (b) Stars with masses from 0.5 to 2 solar mass. (c) Stars with masses greater than 2 solar mass. (d) All stars fuse hydrogen into helium via CNO-cycle regardless of their mass. 26. The planetary nebulae produce light by (a) opalescence. (b) fluorescence. (c) scattering. 27. When the Sun enters the final red giant stage its core will consist of (a) helium nuclei and degenerate electrons. (b) iron nuclei and degenerate electrons. (c) degenerate neutrons. (d) carbon nuclei, some oxygen nuclei and degenerate electrons. 28. The Eagle nebula (or M16) is (a) a planetary nebula. (b) a giant molecular cloud. (c) a supernova remnant. (d) a reflection nebula. 29. There are no hydrogen spectral lines in the spectrum of Type II supernova. 5
Course: ASTR1P02 Date: February 6, 2017 page 6 of 9 pages 30. When does the iron core of a high mass star collapse? (a) When it stops producing neutrinos. (b) When it is ignited by helium flash. (c) When its mass reaches the Chandrasekhar limit. 31. Type II supernova occurs (a) when a regular star is swallowed by a black hole. (b) when a large mass star explodes. (c) when helium starts fusing to carbon in the core of the star. (d) when the mass transfer pushes the mass of a white dwarf to the maximum value it can have. 32. Which of these iron cores of a high mass star has the smallest radius? (a) 1 solar mass iron core. (b) 1.1 solar mass iron core. (c) 1.2 solar mass iron core. 33. Which of these supernovae emits hydrogen spectral lines? (a) Type Ia. (b) Type II. 34. Type II supernovae are important because (a) all of star s hydrogen is returned to the interstellar medium. (b) the resulting burst of neutrinos keeps the galaxy from collapsing. (c) the elements heavier than iron are synthesized and the elements heavier than helium are dispersed through space. 35. Most of the energy released in a Type II supernova is carried by (a) photons (light). (b) neutrinos. (c) the ejected nuclei. 6
Course: ASTR1P02 Date: February 6, 2017 page 7 of 9 pages 36. The Crab nebula is (a) a planetary nebula. (b) a giant molecular cloud. (c) a reflection nebula. (d) a supernova remnant. 37. The Ring nebula is (a) a planetary nebula. (b) a giant molecular cloud. (c) a reflection nebula. (d) a supernova remnant. 38. A pulsar is (a) an unstable star during its yellow giant stage. (b) a fast spinning white dwarf. (c) a fast spinning neutron star. 39. A neutron star is supported against its gravitational collapse by (a) the pressure exerted by degenerate electrons. (b) thermal neutrinos. (c) the pressure exerted by degenerate neutrons. (d) the strong nuclear force. 40. Who was the first to detect pulsars? (a) J. Bell. (b) E. Hubble. (c) A. S. Eddington. (d) H. Shapley. 41. The Schwarzchild radius for 10 solar mass black hole is (a) 3000 km. (b) 300 km. (c) 30 km. (d) 3 km. 7
Course: ASTR1P02 Date: February 6, 2017 page 8 of 9 pages 42. In order to detect a black hole the astronomers look for (a) gravitational waves produced by the black hole. (b) a spot into which stars and their planets fall. (c) a very intense source of infrared radiation. (d) a binary system where a companion star is not visible but it has a mass greater than 3 solar mass and is an intense X-ray source. 43. According to the Einstein s General Theory of Relativity, the stronger is the force of gravity on a clock, the slower is the clock rate. 44. As a source of light approaches the event horizon an observer at a fixed distance from the event horizon will observe the emitted light to have longer and longer wavelengths. This is caused by (a) the cosmological redshift. (b) the Doppler effect. (c) the gravitational redshift. 45. The prediction of the General Theory of Relativity that a mass bends spacetime and that other objects, including photons, move along the paths of shortest distance in the bent spacetime was confirmed by the observed shift in the positions of stars during a total solar eclipse. The person who did the observations was (a) J. Bell. (b) E. Hubble. (c) A. S. Eddington. (d) H. Shapley. 46. Betelgeuse is (a) a planetary nebula. (b) a supernova remnant. (c) a red super-giant. (d) a giant molecular cloud 8
Course: ASTR1P02 Date: February 6, 2017 page 9 of 9 pages 47. Which of these stars is most likely to be the youngest? (a) 15 solar mass star. (b) 5 solar mass star. (c) 1 solar mass star. (d) 0.5 solar mass star. 48. As the spinning object contracts, the spin rate decreases. 49. Which of these are used by astronomers to measure distances of the distant galaxies? (a) Red dwarfs. (b) Emission nebulae. (c) Black Holes. (d) Type Ia supernovae. 50. When the lighter nuclei fuse to form the nucleus of gold the energy is released. 9