1. active prominences - solar prominences that change in a matter of hours

2. active region - photosphere around a sunspot group, can erupt violently and unpredictably

3. active Sun - unpredictable aspects of the Sun’s behavior; sudden, explosive prominences and flares

4. chromosphere - the Sun’s lower atmosphere, just above photosphere

5. conservation of mass and energy - the sum of mass and energy must remain constant

6. convection zone - area of Sun’s interior where material is in constant convection, extends from photosphere to depth of 200,000 km

7. corona - outer atmosphere of Sun, at great distances becomes solar wind

8. coronal hole - large regions of solar atmosphere 10 times denser than normal; here gas streams freely into space, escaping the Sun’s gravity

9. deuteron - hydrogen isotope, produced in the first fusion reaction that powers most stars

10. effective temperature - average temperature of a star’s photosphere, 6000K for our Sun

11. flare - explosive event on the Sun, usually occurs near sunspots

12. fusion - light nuclei are ‘fused’ into heavier ones, releasing energy; generates energy in the Sun’s core

13. GONG - Global Oscillations Network Group

14. granule - topmost part of a solar convection cell, just below photosphere

15. Helioseismology - study of ‘sound’ waves that cross solar interior, reveals interior conditions

16. isotope - nuclei with the same number of protons but different number of neutrons

17. limb - edge of the Sun

18. limb darkening - light from edge is cooler since it is from particles that are not as deep, so edge is darker

19. luminosity - total energy radiated by a star each second

20. Maunder minimum - period between the years 1645 and 1715 with little solar activity, sunspot cycle apparently stopped

21. neutrino - virtually massless and chargeless particle produced by fusion in the Sun

22. neutrino oscillation - possible solution to missing solar neutrino problem, some neutrinos may ‘oscillate’ (be transformed into other particles between the Sun and the Earth)

23. penumbra - outer region of a sunspot, not as dark or cool as the central umbra

24. photosphere - visible surface of the Sun, lies just below chromosphere

25. positron - the antiparticle of the electron, one of the products in the first step of the proton- proton chain

26. prominence - loop or sheet of glowing gas ejected from the surface of the Sun and moving through the inner corona

27. proton-proton chain - chain of fusion reactions, from hydrogen to helium, that powers most stars

28. quiescent prominences - stable prominence, lasting days or weeks, held by Sun’s magnetic field

29. quiet Sun - predictable elements of Sun’s behavior

30. radiation zone - photons travel through this region of the Sun’s interior with relative ease because atoms are stripped of electrons by the high heat

31. solar constant - amount of energy reaching Earth per unit area per unit time

32. solar core - center of Sun, where nuclear reactions occur

33. solar cycle - 22-year period required for Sun’s average number of spots and magnetic polarity to repeat

34. solar disk - surface of Sun that we see

35. solar interior - region between solar core and convection zone

36. solar maximum - part of cycle where sunspot number is at its highest

37. solar minimum - starting point of sunspot cycle, number is at its minimum

38. Standard Solar Model - most accepted picture of the way the Sun behaves

39. star - glowing ball of gas held together by its own gravity and powered by nuclear fusion

40. sunspot - dark area on Sun’s surface, cooler than surrounding area

41. sunspot cycle - fairly regular pattern the number of sunspots follows

42. Supergranulation - large scale granules on the surface of the Sun, cells up to 30,000 km across

43. transition zone - region of rapid temp. increase, separates chromosphere from the corona

44. umbra - darkest, coolest, innermost portion of a sunspot

45. WIMP - Weakly Interacting Massive Particle

1. Name and briefly describe the main regions of the Sun.

Core - nuclear fusion occurs here. Interior - gaseous layer. Convection zone - constant convective motion. Photosphere - surface that we see. Chromosphere - bright lower atmosphere. Corona - upper atmosphere. Solar Wind - escaping particles.

2. How massive is the Sun, compared with the Earth? 300,000 times greater than the mass of the Earth.

3. How hot is the solar surface? The solar core? 6000K at the surface. 15,000,000K at the core.

4. Why does the Sun appear to have a sharp edge? The temperature of the sun increases with depth. Photons coming from the center of the observed disk are more energetic and therefore brighter than those coming from the edge of the disk.

5. What is the solar wind? Fast moving particles escaping the Sun. Produced by high temperature coronal gas.

6. What is a sunspot? A cooler, and therefore darker region of the Sun’s photosphere. Typically areas of concentrated magnetic fields.

7. What is thought to be the cause of sunspots, flares, and prominences? It is believed that the strong magnetic fields in these areas are the causes of all the disturbances in the photosphere.

8. What fuels the Sun’s enormous energy output? Nuclear fusion.

9. As mass decreases in the proton-proton chain, where does it go? It is converted into energy.

10. Why are scientists trying so hard to detect solar neutrinos? Finding the correct output of neutrinos would confirm that the model of the fusion reactions on the Sun is correct.

11. What are some possible explanations for the scarcity of detected neutrinos?

1. The Sun could be pulsating, requiring less energy from fusion that would produce neutrinos. 2. Other material might be present in the core that is not accounted for. 3. Neutrinos could transform into other particles.