Brock University Test 1, January, 2015 Number of pages: 9 Course: ASTR 1P02 Number of Students: 500 Date of Examination: January 29, 2015 Number of hours: 50 min Time of Examination: 18:00 15:50 Instructor: B.Mitrović 1. A 0.025 solar mass protostar will become (a) a black dwarf. (b) a red dwarf. (c) a brown dwarf. 2. A 0.55 solar mass protostar will become (a) a black dwarf. (b) a red dwarf. (c) a brown dwarf. 3. The new stars are born in (a) the reflection nebulae. (b) the emission nebulae. (c) the planetary nebulae. (d) the giant molecular clouds. 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 reflection nebulae. (b) the emission nebulae. (c) the planetary nebulae. (d) the giant molecular clouds. 1
Course: ASTR1P02 Date: January 29, 2015 page 2 of 9 pages 6. The giant molecular clouds are given the name molecular because they contain the molecules of. (a) helium (b) hydrogen (c) amino acids (d) ethyl alcohol 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) Red light. (b) Blue light. 9. The protostars could be observed in the part of the spectrum. (a) gamma-ray (b) X-ray (c) ultraviolet (UV) (d) infrared (IR) 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 less than it is today because the temperature of the fusing core was lower (10 million K) than it is today (15 million K). (b) was the same as it is today because all main sequence stars are in hydrostatic equilibrium. (c) was greater than it is today because it had more hydrogen in its fusion core. 2
Course: ASTR1P02 Date: January 29, 2015 page 3 of 9 pages 12. Once the Sun converts all of the hydrogen in its core to helium it will become (a) a pulsating yellow giant. (b) a red giant. 13. The helium core of a star heats up as a result of (a) pressure created by degenerate electrons. (b) heat produced in hydrogen fusing shell around the helium core. (c) gravitational contraction. 14. A white dwarf emits light because (a) degenerate electrons could drop into the lower energy levels and emit photons in the process. (b) carbon nuclei could drop into the lower energy levels and emit photons in the process. (c) helium nuclei are fusing into carbon with a release of energy. 15. Which of these fusion reactions requires the highest core temperature? (a) Fusion of silicon to iron. (b) Fusion of carbon to neon. (c) Fusion oh helium to carbon. (d) Fusion of hydrogen to helium. 16. Which of these fusion reactions in the core takes the least amount of time? (a) Fusion of silicon to iron. (b) Fusion of carbon to neon. (c) Fusion oh helium to carbon. (d) Fusion of hydrogen to helium. 17. The pressure created by degenerate electrons increases with (a) increasing temperature. (b) increasing electron density. (c) decreasing temperature. 3
Course: ASTR1P02 Date: January 29, 2015 page 4 of 9 pages 18. Which of these nuclei has the highest binding energy per nucleon (proton or neutron)? (a) Gold. (b) Iron. (c) Silicon. (d) Carbon. (e) Helium. 19. The nuclei of gold were formed (a) by the nucleosynthesis in the fusing core of a high mass star. (b) during a supernova as the shock wave and the thermal neutrinos supplied the energy. (c) by fission of uranium formed in the fusing core of a high mass star. 20. Which of these fusion reactions releases the largest amount of energy per reaction? (a) Fusion of silicon to iron. (b) Fusion of carbon to neon. (c) Fusion oh helium to carbon. (d) Fusion of hydrogen to helium. 21. Which of these white dwarfs has the largest radius? (a) 1.3 solar mass white dwarf. (b) 1 solar mass white dwarf. (c) 0.9 solar mass white dwarf. (d) 0.8 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) helium nuclei and degenerate electrons. (b) carbon nuclei, some oxygen nuclei, and degenerate electrons. (c) iron nuclei and degenerate electrons. 4
Course: ASTR1P02 Date: January 29, 2015 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 Newton s law of gravity. (b) the Chandrasekhar limit. (c) the conservation of energy. (d) the conservation of angular momentum. 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) scattering. (b) opalescence. (c) fluorescence. 27. When the Sun enters the final red giant stage its core will consist of (a) helium nuclei and degenerate electrons. (b) carbon nuclei, some oxygen nuclei and degenerate electrons. (c) iron nuclei and degenerate electrons. (d) degenerate neutrons. 28. The Eagle nebula (or M16) is (a) a planetary nebula. (b) a supernova remnant. (c) a giant molecular cloud. (d) a reflection nebula. 29. There are no hydrogen spectral lines in the spectrum of Type II supernova. 5
Course: ASTR1P02 Date: January 29, 2015 page 6 of 9 pages 30. When does the iron core of a high mass star collapse? (a) When it is ignited by helium flash. (b) When its mass reaches the Chandrasekhar limit. (c) When it stops producing neutrinos. 31. Type II supernova occurs (a) when helium stars fusing to carbon in the core of the star. (b) when a regular star is swallowed by a black hole. (c) when a large mass star explodes. (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) 1.2 solar mass iron core. (b) 1.1 solar mass iron core. (c) 1 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) the resulting burst of neutrinos keeps the galaxy from collapsing. (b) the elements heavier than iron are synthesized and the elements heavier than helium are dispersed through space. (c) all of star s hydrogen is returned to the interstellar medium. 35. Most of the energy released in a Type II supernova is carried by (a) photons (light). (b) the ejected nuclei. (c) neutrinos. 6
Course: ASTR1P02 Date: January 29, 2015 page 7 of 9 pages 36. The Crab nebula is (a) a planetary nebula. (b) a giant molecular cloud. (c) a supernova remnant. (d) a reflection nebula. 37. The Ring nebula is (a) a planetary nebula. (b) a giant molecular cloud. (c) a supernova remnant. (d) a reflection nebula. 38. A pulsar is (a) a fast spinning white dwarf. (b) a fast spinning neutron star. (c) an unstable star during its yellow giant stage. 39. A neutron star is supported against its gravitational collapse by (a) thermal neutrinos. (b) the pressure exerted by degenerate neutrons. (c) the pressure exerted by degenerate electrons. (d) the strong nuclear force. 40. Who was the first to detect pulsars? (a) Eddington. (b) Galileo. (c) Jocelyn Bell. (d) Einstein. 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: January 29, 2015 page 8 of 9 pages 42. In order to detect a black hole the astronomers look for (a) a spot into which stars and their planets fall. (b) a very intense source of infrared radiation. (c) 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. (d) gravitational waves produced by the black hole. 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 Doppler effect. (b) the gravitational redshift. (c) the cosmological 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) E. Hubble. (b) A. S. Eddington. (c) H. Shapley. (d) J. Bell. 46. Betelgeuse is (a) a white dwarf. (b) a planetary nebula. (c) a supernova remnant. (d) a red super-giant. 8
Course: ASTR1P02 Date: January 29, 2015 page 9 of 9 pages 47. Which of these stars is most likely to be the youngest? (a) 0.5 solar mass star. (b) 1 solar mass star. (c) 5 solar mass star. (d) 15 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) Pulsars. (b) Black Holes. (c) Type Ia supernovae. (d) Type II supernovae. 50. When the lighter nuclei fuse to form the nucleus of gold the energy is released. 9