EBK LOOSE-LEAF VERSION OF UNIVERSE
11th Edition
ISBN: 9781319227975
Author: KAUFMANN
Publisher: VST
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Chapter 20, Problem 28Q
(a)
To determine
The wavelength of the maximum emission of the white dwarf Sirius B. Also, determine to which region of the
(b)
To determine
The difference in figure 20-9 that the Sirius B appears fainter that its primary star, but in the another image made by an x-ray telescope, Sirius B is brighter than its primary star.
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Many of the bright stars in the night sky are highly luminous normal blue stars (such as Acrux), and others are blue giants (such as Rigel) or red giants (such as Betelgeuse). Generally, such stars have a luminosity of 103 to 105 times that of our Sun!
Ignoring any effects from our atmosphere, how bright would a star with a luminosity of 8380 solar luminosities be if it were located 620 light years from Earth?
(You will need to convert some values.)
W/m²
For comparison, if you were 1 meter from a regular 100 W light bulb, the brightness would be 7.96 W/ m². (Since stars are not this bright, your answer should be considerably less!) Kind of amazing you can see these things, isn't it?
We will take a moment to compare how brightly a white dwarf star shines compared to a red giant star. For the sake of this problem, lets assume a white dwarf has a temperature roughly twice as large as a red giant star. As for their stellar radii, the white dwarf has a radius about 1/10000th that of a red giant star.
With this in mind, how does the luminosity of a red giant star compare to that of a white dwarf? (Put differently, find the ratio of their luminosities a.k.a. how many times more luminous is the red giant than the white dwarf? An answer of less than 1 means the white dwarf is more luminous, an answer of 1 means they have the same luminosity, and an answer greater than 1 means the red giant is more lu
The apparent magnitude of a star is observed to vary between m = +0.4 and m = +0.1 because
the star pulsates and hence continuously changes its radius and temperature. When at its peak
brightness, the star’s radius has increased by a factor of two compared to its value at the mini-
mum brightness. Determine the value of T+/T−, where T+ is the temperature when the star is at
its peak brightness and T− is the temperature when the star is at it minimum brightness.
Note: we expect T+/T− < 1 because the star’s temperature decreases as its radius increases.
Chapter 20 Solutions
EBK LOOSE-LEAF VERSION OF UNIVERSE
Ch. 20 - Prob. 1CCCh. 20 - Prob. 2CCCh. 20 - Prob. 3CCCh. 20 - Prob. 4CCCh. 20 - Prob. 5CCCh. 20 - Prob. 6CCCh. 20 - Prob. 7CCCh. 20 - Prob. 8CCCh. 20 - Prob. 9CCCh. 20 - Prob. 10CC
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