2. Fusion Reactions in the Sun

4. The Electromagnetic Spectrum

7. The Sun is a Magnet
The field is dragged by the rotation, and flips polarity every
11 years

13. A Solar Prominence

15. The Solar Wind

18. Charged particles spiral into Earth’s magnetic field; collide with atmospheric atoms and excite electrons into higher energy levels; when the electrons return to ground state, they emit visible light

19. The Aurora Borealis (Northern Lights)

23. As helium builds up in core, star expands in size

24. Outer layers are eventually blown off to become a
planetary nebula

25. The Future of Our Sun

28. What about larger stars than our Sun?
There are larger stars than our Sun?
Yes
In heavier stars, gravity causes the core to get
hot enough to cause other reactions:

30. Elements keep fusing until they get to iron
Iron is the fusion “dead end”

31. Once reactions stop, outward pressure quickly drops to zero

32. Once reactions stop, outward pressure quickly drops to zero
Gravity quickly causes the star to collapse inward
Rebound pressure causes the star to explode
Supernova!

34. Stars of about 7-10 solar masses have cores that
form neutron stars

35. Stars of more than 10 solar masses
have cores that form black holes

36. Type I Supernova
Occur in multiple-star systems
One star is a white dwarf that draws matter from
other star
When mass of white dwarf is 1.4 times the
mass of our Sun (the Chandrasekhar Limit),
it supernovas
Always has same magnitude (brightness), so can be
used to measure distance

40. Black-body Radiators

42. Wien’s Law: λpeak T = 2.898 x 10-3 m K

43. The Hertzsprung-
Russell Diagram
Annie Jump Cannon
( )

44. The Hertzsprung-Russell Diagram