Problem_Set_07

# Problem_Set_07 - PROBLEM SET 7 Physics 2022 1 The central...

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PROBLEM SET 7 Physics 2022 1. The central star in a newly formed planetary nebula has a luminosity of 1000 L ʘ and a surface temperature of 100,000 K. What is the star’s radius? Give your answer as a multiple of the Sun’s radius. 2. The Ring Nebula in the constellation Lyra has an angular size of 1.2 arcmin x 1.2 arcmin. It is expanding at the rate of about 20 km/s. Approximately how long ago did the central star shed its outer layers? Assume that the nebula is 2,700 ly from Earth. 3. (a) Calculate the wavelength of maximum emission of the white dwarf Sirius B if its surface T = 30,000 K. In what part of the electromagnetic spectrum does this wavelength lie? (b) In a visible-light photograph, Sirius B appears much fainter than its primary star. But in an image made with an X-ray telescope, Sirius B is the brighter star. Explain the difference. 4. Find the average density (g/cm 3 ) of a 1-M ʘ white dwarf having the same diameter as the Earth. 5. In the classic 1960’s science-fiction comic book The Atom , a physicist discovers a basketball-
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