19. Why does the Sun stay about the same size? 20. What is the difference about the fusion in a main sequence star, red giant and red supergiant? 21. Describe the fate of a star the size of our Sun. 22. What will probably happen to VY Canis Majoris a star 950 times the size of the Sun? 23. VY Canis Majoris is 5,000 light-years from Earth, what does that mean?

 Rocks on Earth ◦ 4.2 billion years  Oldest stars ◦ billion years  Universe must be older ◦ Estimate backwards ◦ 13.8 billion years

 Big Crush ◦ Stops expanding ◦ Gravity causes to crush ◦ Repeat the process  Big Chill ◦ Expand at slowing rate ◦ Get cooler as expands  Big Rip ◦ Expand at increasing rate ◦ Everything gets ripped apart

 Visible matter  Dark matter ◦ Does not give off light ◦ Things weigh more than they should  Dark energyenergy ◦ Causing the increase in expansion rate seen in most recent data ◦ Thus fate of the universe is…  Big Rip  Adding these items makes models better fit actual observations

24. How old is the universe estimated to be? 25. Describe the three hypotheses about the fate of the universe. 26. How is dark matter and dark energy different from all other matter and energy? 27. Of the items we have talked about in class, what do you think we should research further and why?

 Distances in space are very large  Created new unit - Light year ◦ Distance ◦ 9.5×10 12 km or 5.9×10 12 mi  Proxima Centauri : 2.5 x miles