1. Rotational Mathematics
Modified from
Janet Moore
NASA Educator Ambassador

2. Merry-Go-Round

3. Merry-Go-Round

4. Solar System

5. Solar System

6. Solar System

7. Solar System

8. In Summary - Solar System
Orbital speed depends on force of gravity
Force of gravity depends on mass within the radius
Therefore, orbital speed depends on mass within the radius

9. What About Galaxies?
How would you expect stars to move around in a spiral galaxy?
What would you expect the mass distribution in a spiral galaxy to be?

10. The Activity - NGC 2742 You will be given:
Rotation Curve (velocity vs. radius)
Luminosity Curve (luminosity vs. radius)
Use the Data Chart to analyze the mass in the galaxy
G = 4.31 x 10-6

11. Sample Data Chart Radius Rot. Vel. Grav. Mass Lum. Lum. Mass Lum/Grav1 80
1.5 e9
3 e8
6 e8
0.4 3
100
6.9 e9
1 e9
2 e9
0.29 5
120
1.7 e10
4 e9
0.24 8
140
3.6 e10
3.5 e9
7 e9
0.19

12. Evidence for Dark Matter
Light (visible matter) drops off as you go farther out in a galaxy
BUT Velocities do not drop off
Result: Dark Matter mass is about 10x Luminous Matter mass

13. What is Dark Matter? Baryonic (Normal) Matter:
Low mass stars, brown dwarfs (likely), large planets, meteoroids, black holes, neutron stars, white dwarfs, hydrogen snowballs, clouds in halo.
Non-Baryonic (Exotic) Matter:
Hot Dark Matter: fast-moving at time of galaxy formation, eg massive neutrinos
Cold Dark Matter: slow-moving at times of galaxy formation, eg WIMPs -- particle detector experiments looking for them

14. NASA’s Fermi Mission Formerly known as the GLAST mission
Launched June 11, 2008
Studying gamma ray sources in the universe
Studying potential sources of dark matter in the universe

15. NEWTON’S LAWS 11:00 am - Room 207
Questions?
Janet Moore
epo.sonoma.edu
My Other Workshops:
NEWTON’S LAWS 11:00 am - Room 207
PI IN THE SKY 3:30 pm - Room 262