Stellar Astrophysics — MCQs

1. Which process powers the main sequence stars?
(A) Nuclear fission
(B) Nuclear fusion of hydrogen
(C) Radioactive decay
(D) Gravitational collapse

2. What is the final fate of a star with mass less than 8 solar masses?
(A) Black hole
(B) Neutron star
(C) White dwarf
(D) Supernova remnant

3. What is the Chandrasekhar limit approximately equal to?
(A) 5 solar masses
(B) 1.4 solar masses
(C) 0.5 solar masses
(D) 10 solar masses

4. In the Hertzsprung–Russell diagram, the main sequence represents stars:
(A) In the planetary nebula phase
(B) Burning hydrogen in their cores
(C) Collapsing into black holes
(D) Evolving into red giants

5. What type of star is the Sun classified as?
(A) Red giant
(B) White dwarf
(C) G-type main sequence star
(D) Neutron star

6. What is the primary energy source of red giant stars?
(A) Helium fusion
(B) Hydrogen fusion in the core
(C) Hydrogen shell burning
(D) Gravitational contraction only

7. What is the remnant left after a Type II supernova?
(A) White dwarf
(B) Neutron star or black hole
(C) Red giant
(D) Planetary nebula

8. Cepheid variables are important because they:
(A) Help determine cosmic distances
(B) Are sources of gamma-ray bursts
(C) Form neutron stars directly
(D) Indicate starspot cycles

9. What does the mass–luminosity relation indicate?
(A) More massive stars are less luminous
(B) Stellar mass and luminosity are unrelated
(C) More massive stars are more luminous
(D) Luminosity depends only on age

10. Which type of stars end as planetary nebulae?
(A) High-mass stars
(B) Low and intermediate-mass stars
(C) Neutron stars
(D) Supermassive stars

11. Which particles are produced in large quantities during core-collapse supernovae?
(A) Protons
(B) Neutrons
(C) Neutrinos
(D) Photons only

12. What is the dominant pressure supporting white dwarfs?
(A) Gas pressure
(B) Radiation pressure
(C) Electron degeneracy pressure
(D) Magnetic pressure

13. What is the dominant pressure supporting neutron stars?
(A) Gas pressure
(B) Electron degeneracy pressure
(C) Neutron degeneracy pressure
(D) Radiation pressure

14. The main cause of supernova explosions in massive stars is:
(A) Runaway nuclear fusion
(B) Core collapse due to iron formation
(C) Excessive radiation pressure
(D) Stellar rotation

15. Which color stars are the hottest?
(A) Red
(B) Yellow
(C) Blue
(D) Orange

16. Which law relates luminosity, radius, and temperature of a star?
(A) Stefan–Boltzmann law
(B) Kepler’s law
(C) Wien’s law
(D) Ohm’s law

17. What type of variable stars are caused by pulsations in radius and temperature?
(A) Eclipsing binaries
(B) Cepheids and RR Lyrae
(C) Supernovae
(D) White dwarfs

18. What is the main characteristic of Population II stars?
(A) High metallicity
(B) Very low metallicity
(C) They are very young
(D) Found only in spiral arms

19. What is the approximate surface temperature of the Sun?
(A) 2,000 K
(B) 5,800 K
(C) 12,000 K
(D) 25,000 K

20. What happens in the triple-alpha process?
(A) Hydrogen fuses into helium
(B) Three protons form helium
(C) Three helium nuclei form carbon
(D) Carbon fuses into oxygen

21. What stellar object emits pulses of radiation due to rapid rotation?
(A) Red giant
(B) White dwarf
(C) Pulsar
(D) Black hole

22. Which stellar property determines its evolution most strongly?
(A) Radius
(B) Mass
(C) Temperature
(D) Luminosity

23. What is the Eddington limit?
(A) Maximum radius of a star
(B) Maximum luminosity before radiation pressure blows material away
(C) Minimum star temperature
(D) Age limit of stars

24. Which type of binary stars provide direct stellar mass measurements?
(A) Optical doubles
(B) Spectroscopic binaries
(C) Eclipsing binaries
(D) Runaway stars

25. Which process prevents stars below 0.08 solar masses from igniting hydrogen fusion?
(A) Rapid cooling
(B) Electron degeneracy pressure
(C) Lack of helium
(D) High metallicity

26. What are such objects called (below 0.08 solar masses)?
(A) Neutron stars
(B) Brown dwarfs
(C) White dwarfs
(D) Pulsars

27. Which process creates most of the elements heavier than iron?
(A) Big Bang nucleosynthesis
(B) Stellar core fusion
(C) Supernova nucleosynthesis (r-process)
(D) Radioactive decay

28. What determines the color of a star?
(A) Mass only
(B) Surface temperature
(C) Age only
(D) Luminosity only

29. Which star property can be determined by observing Doppler shifts in binaries?
(A) Radius
(B) Mass
(C) Luminosity
(D) Surface gravity

30. What are T Tauri stars?
(A) Old white dwarfs
(B) Young pre-main-sequence stars
(C) Red supergiants
(D) Neutron stars

31. Stars with masses greater than about 25 solar masses often end their lives as:
(A) White dwarfs
(B) Neutron stars
(C) Black holes
(D) Planetary nebulae

32. Which nuclear cycle dominates energy production in high-mass stars?
(A) Proton–proton chain
(B) CNO cycle
(C) Triple-alpha process
(D) r-process

33. Which property of stars can be measured from parallax?
(A) Mass
(B) Temperature
(C) Distance
(D) Luminosity

34. What is the approximate age of the Sun?
(A) 1 billion years
(B) 4.6 billion years
(C) 10 billion years
(D) 15 billion years

35. White dwarfs cool and fade because they:
(A) No longer undergo nuclear fusion
(B) Burn hydrogen slowly
(C) Collapse into neutron stars
(D) Radiate heat from fusion reactions

36. What is the escape velocity at the surface of a neutron star?
(A) A few km/s
(B) Thousands of km/s
(C) A significant fraction of the speed of light
(D) Equal to Earth’s escape velocity

37. Which type of star cluster contains mostly old Population II stars?
(A) Open clusters
(B) Globular clusters
(C) Associations
(D) Moving groups

38. In stellar nucleosynthesis, oxygen is primarily formed by:
(A) Fusion of helium and carbon
(B) Proton capture on hydrogen
(C) Neutron capture
(D) Radioactive decay

39. Which phenomenon explains widening of spectral lines in stars?
(A) Zeeman effect
(B) Doppler broadening
(C) Stark effect
(D) All of the above

40. What is the primary mechanism of energy transport in the Sun’s core?
(A) Radiation
(B) Convection
(C) Conduction
(D) Neutrino transport

41. Which type of binary star system leads to a Type Ia supernova?
(A) Two red giants
(B) White dwarf accreting matter from a companion
(C) Neutron star and black hole
(D) Two T Tauri stars

42. What is the approximate lifetime of a massive O-type star?
(A) Billions of years
(B) Millions of years
(C) Thousands of years
(D) Same as Sun

43. What is the solar corona’s temperature compared to the photosphere?
(A) Cooler
(B) Similar
(C) Much hotter
(D) Equal to Earth’s atmosphere

44. Which star property can be measured directly by interferometry?
(A) Radius
(B) Temperature
(C) Mass
(D) Luminosity

45. What phenomenon is responsible for pulsations in Cepheid stars?
(A) Opacity changes in helium ionization zone
(B) Shock waves
(C) Magnetic field oscillations
(D) Binary interaction

46. Which element builds up in the core of massive stars before supernova collapse?
(A) Carbon
(B) Silicon
(C) Iron
(D) Nickel

47. Stars with masses between 8–25 solar masses usually end as:
(A) Planetary nebulae
(B) Neutron stars
(C) Black holes
(D) White dwarfs

48. What is the Roche lobe in binary systems?
(A) Region where gravitational influence of each star dominates
(B) The luminosity limit
(C) Accretion disk radius
(D) Planetary orbit region

49. What is the approximate diameter of a typical white dwarf?
(A) Similar to Earth’s
(B) Similar to Jupiter’s
(C) Similar to Sun’s
(D) A few kilometers

50. Which stage will the Sun enter after exhausting core hydrogen?
(A) Neutron star
(B) Red giant
(C) Supernova
(D) Black hole