T1

1. How do astronomers determine the Sun’s size, distance, temperature, composition, and mass?
   By using measurements such as angular size, parallax, spectral lines, and solar models.

2. How is energy transported from the core to the surface of the Sun?
   Through radiation in the inner layers and convection in the outer layers.

3. What are the interior and atmospheric layers of the Sun?
   Core, radiative zone, convective zone, photosphere, chromosphere, and corona.

4. What does granulation on the Sun’s surface reveal?
   It shows convection currents just below the photosphere.

5. What is helioseismology and its significance?
   The study of solar oscillations, revealing information about the Sun's interior.

6. Describe the solar atmosphere’s heat profile and the heating of the corona.
   The temperature increases with height; magnetic reconnection and waves heat the corona.

7. What is the Sun’s magnetic cycle and the Babcock model?
   An 11-year cycle explained by the winding and tangling of magnetic fields due to differential rotation.

8. What are magnetic phenomena observed on the Sun?
   Sunspots, prominences, solar flares, and coronal mass ejections (CMEs).

9. What is the solar wind and the solar constant?
   Solar wind is charged particles streaming from the Sun; solar constant is the energy Earth receives.

10. What process powers the Sun’s energy?
    Nuclear fusion through the proton-proton chain.

11. What is the Coulomb barrier?
    The electrostatic repulsion that nuclei must overcome to fuse, overcome by high temperatures.

Module 2 – The Family of Stars (Chapter 9)

12. Why is knowing a star’s distance important?
    It allows calculation of luminosity, size, and other physical properties.

13. How is stellar parallax used?
    To calculate a star’s distance by measuring its apparent motion relative to distant stars.

14. What is a parsec?
    A unit of distance equal to 3.26 light-years, derived from parallax angle.

15. How does proper motion relate to distance?
    Stars with greater proper motion tend to be closer to Earth.

16. What’s the difference between apparent and intrinsic brightness?
    Apparent is how bright it looks; intrinsic is its true brightness regardless of distance.

17. How is absolute visual magnitude found?
    Using the apparent magnitude and the known distance.

18. What is luminosity?
    The total energy a star emits per second.

19. What is the Balmer Thermometer?
    A method using hydrogen absorption lines to estimate surface temperature.

20. How are stellar spectral types classified?
    By temperature and spectral lines: O, B, A, F, G, K, M.

Module 3 – Family of Stars (continued)

21. What defines stellar luminosity?
    It depends on a star’s radius and surface temperature.

22. What is the Luminosity-Radius-Temperature equation?
    L = 4πR²σT⁴ — relates energy output to size and temperature.

23. What is the H-R Diagram?
    A graph plotting stars’ luminosity vs. temperature, showing main sequence, giants, and dwarfs.

24. How do we know giant stars are large and dwarfs are small?
    From luminosity and temperature; giants are luminous but cooler, implying large radius.

25. Why are binary stars important?
    They allow calculation of stellar masses through gravitational effects.

26. How is mass calculated in binary systems?
    Using Newton’s version of Kepler’s 3rd law.

27. What are the three types of binary stars?
    Visual, spectroscopic, and eclipsing binaries.

28. Why are spectroscopic binaries less useful for mass?
    They offer limited data, usually just radial velocity curves.

29. What can eclipsing binaries reveal?
    Mass, radius, and luminosity of both stars through timing and brightness variations.

30. What is the Mass-Luminosity Relation?
    A formula showing more massive stars are significantly more luminous: L ∝ M^3.5.

Module 4 – The Interstellar Medium (Chapter 10)

31. What is the interstellar medium (ISM)?
    Gas and dust that fills space between stars.

32. What are nebulae and their types?
    Clouds in space: emission nebulae, reflection nebulae, and dark nebulae.

33. What observations prove the ISM exists?
    Extinction, reddening, and absorption lines.

34. What is interstellar extinction?
    Dimming of starlight by dust in the ISM.

35. What is interstellar reddening?
    Scattering of blue light, making stars appear redder.

36. How are interstellar absorption lines identified?
    They are narrow and differ from stellar lines in spectra.

37. What are forbidden lines in ISM?
    Spectral lines not normally seen on Earth, indicating low-density environments.

38. What is 21-cm radiation?
    Radio waves from hydrogen atoms, used to map ISM.

39. What are the four components of the ISM?
    Cold neutral medium, warm neutral medium, warm ionized medium, hot ionized medium.

40. What is the Gas-Stars-Gas Cycle?
    The cycle of gas forming stars, stars evolving, and returning gas to the ISM.