Stellar Evolution Review

1. Stellar Evolution Review

2. 12-1. Protostars are not seen in visible light telescopes because: • a) they don’t emit any radiation • b) they are surrounded by clouds of gas and dust • c) they only emit infrared radiation • d) they are all moving away from Earth so fast that their visible light is Doppler shifted into the infrared

3. 12-1. Protostars are not seen in visible light telescopes because: • a) they don’t emit any radiation • b) they are surrounded by clouds of gas and dust • c) they only emit infrared radiation • d) they are all moving away from Earth so fast that their visible light is Doppler shifted into the infrared

4. 12-2. A brown dwarf is best described as: • a) a low mass object that doesn’t fuse in its core • b) a low mass main sequence star • c) a high mass main sequence star

5. 12-2. A brown dwarf is best described as: • a) a low mass object that doesn’t fuse in its core • b) a low mass main sequence star • c) a high mass main sequence star

6. 12-3. Why are A-type main sequence stars hotter than G-type main sequence stars? • a) A-type stars have cores of metal, whereas G-type stars do not • b) A-type stars have more fusion on their surface than G-type stars • c) A-type stars have more fusion in their cores than G-type stars • d) A-type stars fuse in their cores and near their surfaces, while G-type stars only fuse in their cores.

7. 12-3. Why are A-type main sequence stars hotter than G-type main sequence stars? • a) A-type stars have cores of metal, whereas G-type stars do not • b) A-type stars have more fusion on their surface than G-type stars • c) A-type stars have more fusion in their cores than G-type stars • d) A-type stars fuse in their cores and near their surfaces, while G-type stars only fuse in their cores.

8. 12-4. Where on the H-R diagram are the majority of stars located? • a) as white dwarves • b) on the main sequence • c) as giants • d) as supergiants

9. 12-4. Where on the H-R diagram are the majority of stars located? • a) as white dwarves • b) on the main sequence • c) as giants • d) as supergiants

10. 12-5. Which type of star is forming iron in its core? • a) supergiant • b) giant • c) main sequence • d) white dwarf

11. 12-5. Which type of star is forming iron in its core? • a) supergiant • b) giant • c) main sequence • d) white dwarf

12. 12-6. The Orion nebula is • a) a reflection nebula illuminated by newly formed stars. • b) an emission nebula heated by newly formed stars. • c) a supernova remnant. • d) a dark nebula.

13. 12-6. The Orion nebula is • a) a reflection nebula illuminated by newly formed stars. • b) an emission nebula heated by newly formed stars. • c) a supernova remnant. • d) a dark nebula.

14. 12-7. What happens when a protostar joins the main sequence? • a) Its surface area increases significantly. • b) Its luminosity increases significantly. • c) Nuclear fusion begins in its core. • d) Nuclear fission begins in its core.

15. 12-7. What happens when a protostar joins the main sequence? • a) Its surface area increases significantly. • b) Its luminosity increases significantly. • c) Nuclear fusion begins in its core. • d) Nuclear fission begins in its core.

16. 12-8. An object is found that emits most of its electromagnetic radiation in the infrared. This object could be a • a) protostar. • b) G-type star. • c) B-type star. • d) cool gas cloud.

17. 12-8. An object is found that emits most of its electromagnetic radiation in the infrared. This object could be a • a) protostar. • b) G-type star. • c) B-type star. • d) cool gas cloud.

18. 12-9. We see an emission nebula via • a) reflected blue light from a nearby star. • b) blue light emitted by hot (excited) hydrogen atoms. • c) red light emitted by hot (excited) hydrogen atoms. • d) reflected red light from a nearby star.

19. 12-9. We see an emission nebula via • a) reflected blue light from a nearby star. • b) blue light emitted by hot (excited) hydrogen atoms. • c) red light emitted by hot (excited) hydrogen atoms. • d) reflected red light from a nearby star.

20. 12-10. Which of the following are thought to be mechanisms that cause a giant molecular cloud to collapse and form a protostar? • a) The shockwave from a nearby supernova • b) The shockwave from a newly formed high-mass star that is nearby • c) The shockwave experienced by the cloud as it passes through a spiral arm • d) All of the above

21. 12-10. Which of the following are thought to be mechanisms that cause a giant molecular cloud to collapse and form a protostar? • a) The shockwave from a nearby supernova • b) The shockwave from a newly formed high-mass star that is nearby • c) The shockwave experienced by the cloud as it passes through a spiral arm • d) All of the above

22. 12-12. Red giants burn helium via nuclear fusion in their core. The ash (end product) of this nuclear fusion is • a) iron. • b) hydrogen. • c) lithium and carbon. • d) carbon and oxygen.

23. 12-12. Red giants burn helium via nuclear fusion in their core. The ash (end product) of this nuclear fusion is • a) iron. • b) hydrogen. • c) lithium and carbon. • d) carbon and oxygen.

24. 12-13. Where is the Sun located on this H-R diagram? • a) A • b) B • c) C • d) D • e) E

25. 12-13. Where is the Sun located on this H-R diagram? • a) A • b) B • c) C • d) D • e) E

26. 12-14. Which stars on this H-R diagram are on the main sequence? • a) Vega, Sirius A, & Mira • b) Stars at letters A & B & Barnard’s Star • c) Sirius A & Sirius B • d) Rigel & Deneb • e) Pollux & Barnard’s Star

27. 12-14. Which stars on this H-R diagram are on the main sequence? • a) Vega, Sirius A, & Mira • b) Stars at letters A & B & Barnard’s Star • c) Sirius A & Sirius B • d) Rigel & Deneb • e) Pollux & Barnard’s Star

28. 13-1. A nova is believed to occur when which of the following pairs of stars are in a binary system? • a) white dwarf, main sequence star • b) white dwarf, neutron star • c) neutron star, red giant • d) a pair of supergiants

29. 13-1. A nova is believed to occur when which of the following pairs of stars are in a binary system? • a) white dwarf, main sequence star(when the main sequence star expands as it ages…) • b) white dwarf, neutron star • c) neutron star, red giant • d) a pair of supergiants

30. 13-2. What is the most dense element formed in the cores of any stars? • a) helium • b) lead • c) iron • d) carbon

31. 13-2. What is the most dense element formed in the cores of any stars? • a) helium • b) lead • c) iron • d) carbon

32. 13-3. Which type of star is not fusing anything in its core? • a) main sequence • b) giant • c) supergiant • d) neutron star

33. 13-3. Which type of star is not fusing anything in its core? • a) main sequence • b) giant • c) supergiant • d) neutron star

34. 13-4. A pulsar is best described as a: • a) a rapidly rotating white dwarf • b) a rapidly rotating neutron star • c) an expanding and contracting white dwarf • d) an expanding and contracting neutron star

35. 13-4. A pulsar is best described as a: • a) a rapidly rotating white dwarf • b) a rapidly rotating neutron star • c) an expanding and contracting white dwarf • d) an expanding and contracting neutron star

36. 13-5. White dwarves are composed primarily of: • a) helium • b) neutrons • c) carbon and oxygen • d) iron

37. 13-5. White dwarves are composed primarily of: • a) helium • b) neutrons • c) carbon and oxygen • d) iron

38. 13-6. The diameter of a white dwarf is closest to which of the following? • a) about 1 A.U. • b) about the diameter of the Sun • c) about the diameter of the Earth • d) about 10 kilometers

39. 13-6. The diameter of a white dwarf is closest to which of the following? • a) about 1 A.U. • b) about the diameter of the Sun • c) about the diameter of the Earth • d) about 10 kilometers

40. 13-7. The Sun will end its “life” as a(n): • a) supernova. • b) nova. • c) planetary nebula.

41. 13-7. The Sun will end its “life” as a(n): • a) supernova. • b) nova. • c) planetary nebula.

42. 13-9. Explosions on the surfaces of white dwarves in binary star systems are called: • a) novas • b) supernovas • c) flares • d) planetary nebulas

43. 13-9. Explosions on the surfaces of white dwarves in binary star systems are called: • a) novas • b) supernovas • c) flares • d) planetary nebulas

44. 13-10. Rotating neutron stars with off-axis magnetic fields are called: • a) white dwarves • b) pulsars • c) quasars • d) nebulae

45. 13-10. Rotating neutron stars with off-axis magnetic fields are called: • a) white dwarves • b) pulsars • c) quasars • d) nebulae

46. 13-11. A 15 M main sequence star will eventually shed mass as a: • a) supernova. • b) nova. • c) planetary nebula. • d) Cepheid

47. 13-11. A 15 M main sequence star will eventually shed mass as a: • a) supernova. • b) nova. • c) planetary nebula. • d) Cepheid

48. 13-12. A one solar mass star will • a) go through a red giant phase and end its life as a white dwarf. • b) not go through a red giant phase and end its life as a white dwarf. • c) go through a red giant phase and end its life as a black hole. • d) not go through a red giant phase and end its life as a black hole.

49. 13-12. A one solar mass star will • a) go through a red giant phase and end its life as a white dwarf. • b) not go through a red giant phase and end its life as a white dwarf. • c) go through a red giant phase and end its life as a black hole. • d) not go through a red giant phase and end its life as a black hole.

50. 13-13. White dwarfs usually have surface temperatures well above 10,000 K, yet they have extremely low luminosity. Why is this? • a) They are very far away. • b) They have a very large surface area. • c) They emit most of their radiation in the far infrared. • d) They have a very small surface area.