EBK PHYSICS FOR SCIENTISTS & ENGINEERS
5th Edition
ISBN: 9780134296074
Author: GIANCOLI
Publisher: VST
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Chapter 44, Problem 51GP
To determine
The ratio of the diameter of the two stars that have spectra peaks at
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An astronomical image shows two objects that have the same apparent magnitude, i.e., the same brightness. However, spectroscopic follow up observations indicate that while one is a star that is within our galaxy, at a distance dgal away, and has the same luminosity as the Sun, the other is a quasar and has 100x the luminosity of the entire Milky Way galaxy. What is the distance to the quasar? (You may assume, for this rough calculation, that the Milky Way has 1011 stars and that they all have the luminosity as the Sun.) Give your response in Mpc. Value: dgal = 49 pc
Problem 3:
Two stars, M and N, from the same galaxy (at the same distance from
earth) are observed to have the same luminosity (that is, they emit the
same amount of energy per unit time). Star M is red, its spectrum peaks
2.4 × 1015s-1 while star N is white, its spectrum peaks at w =
3.6 x 1015s-1. Assuming that both stars radiate as black body, what is the
at w =
ratio of their radii?
Assuming stars to behave as black bodies stefan-boltzmann law to show that the luminosity of a star is related to its surface temperature and size in the following way:
L = 4(3.14)R^2oT^4
where o= 5.67 ×10^-8 Wm^-2 K-4 is the stefan- boltzmann constant. Then use this expression together with the knowledge that the sun has a surface temperature of 5700k and radius 695 500km to calculate the luminosity of the Sun in units of Watts
Chapter 44 Solutions
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