1. Star A is radiating four times as much energy as star B, but it is two times the distance from us. Which star will appear brighter, and by how much?
2. Two stars have the same absolute magnitude. One is two thousand time farther away than the other. What is the difference in apparent magnitudes?which magnitude larger?
3. Two star have the same apparent magnitude and are of the same spectral type. One is twice as far away as the other. What is the relative the relative size of two stars?
4. A quasar is observed and it is found that a line whose rest wavelenght is 3000 A(Angstrom) it observed at 15000 A. Estimate :
a. How fast is the quasar receding?
b. How far away is its distance is given by the hubble relation?
(the hubble constan is H = 73 km/sec/Mpc)?
Both answer may be done with an accuracy 30%.
5. Let’s assume you discover a new starand you measure an apparent visual magnitude of 7.66, a parallaxof 0.31 arcsec and a recessional velocity of 53 km/sec (it moves awa from us with 53 km/sec).
a. Calculate the absolute magnitude
b. Calculate the diameter of that star in solar units.
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