Problem_Set_09

# Problem_Set_09 - PROBLEM SET 9 Physics 2022 1 An RR Lyrae...

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PROBLEM SET 9 Physics 2022 1. An RR Lyrae star whose peak luminosity is 88 L ʘ is in a globular cluster. At its peak luminosity, this star’s apparent magnitude is +14.3. Determine the distance to this globular cluster in parsecs. 2. Calculate the energy (in Joules) of the photon emitted when a hydrogen atom undergoes a spin-flip transition. 3. A gas cloud located in the spiral arm of a distant galaxy is observed to have an orbital velocity of 400 km/s. If the cloud is 20,000 pc from the center of the galaxy and is moving in a circular orbit, find (a) the orbital period (in years) of the cloud and (b) the mass (in solar masses) of the galaxy contained within the cloud’s orbit. 4. According to the Galaxy’s rotation curve, a star 16 kpc from the galactic center has an orbital speed of about 270 km/s. Calculate (a) the orbital period in years and (b) the mass (in solar masses) within that star’s orbit. 5. (a) Calculate the Schwarzschild radius of a supermassive black hole of mass 3.7 x 10 6 M ʘ , the estimated mass of the black hole at the galactic center.
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