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Absolute Magnitude Questions Try to do these without looking at your notes first! 1. Define the absolute magnitude of a star 2. Explain how it is based on luminosity. 3. State the relation between apparent magnitude m, absolute magnitude M and distance r. 4. Derive the absolute magnitude equation using the inverse square law of radiation. 5. For Rigel, apparent magnitude m=+0.3 and absolute magnitude M=-7.5, calculate the distance to Rigel. 6. The star Sirius has an apparent an absolute magnitude of +1.42 and is at a distance of 2.64pc. Calculate its apparent magnitude. 7. The star Canopus has an apparent magnitude of -0.72 and is at a distance of 96 parsecs. Calculate its absolute magnitude. 8. Calculate the absolute magnitude of the Sun given its apparent magnitude is about -27. For those that like a challenge… 9. You observe a Cepheid variable star in the Andromeda galaxy whose brightness varies with a period of 30 days. If its apparent magnitude varies around a figure of +19.5:a. Calculate the distance to the Andromeda galaxy in light years. b. What is the absolute magnitude of Andromeda if its apparent magnitude is +4.4. If you really, really like a challenge… c. Express intensity, I, in terms of an object’s luminosity, L and the distance to that object, r. d. Estimate how many stars there are in the Andromeda galaxy assuming each star’s luminosity is equal to that of the Sun.