1. Stellar Magnitudes and Exponentials

2. Exponents 5 2 = 5x5= 25 6 3 = 6x6x6 = 216 7 4 = 7x7x7x7 = 2401 4 -2 = 1/4 2 = 1/16 =0.0625 5 2.3 = 40.52

3. Stellar Magnitudes Based on the brightness of stars Used in comparing the brightness of two stars An arbitrary scale not an absolute scale In science and math “arbitrary” just means your making a scale for comparison. There is no in natural absolute for what you are doing.

4. What is an Arbitrary Scale? It’s a scale that is made up. Example- the Celsius Temperature Scale Freezing point of water 0 o Boiling point of water 100 o Divide the distance on thermometer with 100 marks

5. Kelvin Scale an Absolute Scale Based on absolute zero- all molecular motion stops 0 Kelvin = -273 o Celsius

6. Number Line

7. Stellar Magnitude MagnitudeExample -25The Sun -26.7 -20 -15 -10The Moon -12.6 -5Venus -4.4

8. Stellar Magnitude MagnitudeExample 0Sirius -1.4 Brightest star +5+6 Naked Eye Limit +10+10 Binocular Limit +15Pluto +15.1 +20Largest Telescope (visual limit)

9. Stellar Magnitude MagnitudeExample +25 +30 Hubble Space Telescope and large Earth Based Telescopes Photo Graphic Limit +30

10. Stellar Magnitude Based on an Arbitrary Scale Base is 2.512 2.512 5 = 100 The stellar magnitude Scale is an exponential scale A magnitude difference of 5 equal a brightness difference of 100 Greek Astronomer Hipparchus

11. Sample Problem Proxima Centauri apparent magnitude +11.09 Alpha Centauri A apparent magnitude -0.01 Distance on the number line 11.1 Which star is brighter? Could you see Proxima Centauri without a telescope? Could you see Alpha Centauri A without a telescope?

12. Sample Problem How much brighter is Alpha Centauri A than Proxima Centauri? 2.512 11.1 = 27,556.11 The apparent brightness of Alpha Centauri A is 27,556.11 times as bright as Proxima Centauri Notice this is a method for comparing it is not an absolute scale.