Explorations: Introduction to Astronomy (Arny), 6th Edition

Chapter 13: Measuring the Properties of Stars

Problems

1
The star Rigel radiates most strongly at about 200 nanometers. How hot is it?
2
The bright southern star a Centauri radiates most strongly at about 500 nanometers. What is its temperature? How does this compare to the Sun's?
3
Arcturus is about half as hot as the Sun but is about 100 times more luminous. What is its radius compared to the Sun's?
4
A stellar companion of Sirius has a temperature of about 27,000 K and a luminosity of about 1022 Lsun. What is its radius compared to the Sun's? What is its radius compared to the Earth's?
5
Sirius has a parallax of 0.377 arc seconds. How far away is it?
6
The parallax of Proxima Centauri is about 0.763 arc seconds. How far away is it?
7
The parallax of the red giant Betelgeuse is just barely measurable and has a value of about 0.005 arc seconds. What is its distance? Suppose the measurement is in error by ± 0.003 arc seconds. What limits can you set on its distance?
8
Two stars in a binary system have an orbital period, P, of 5 years and an orbital separation, a, of 10 AUsun. What is their combined mass?
9
Two stars in a binary system have an orbital period, P, of 2 years and an orbital separation, a, of 4 AU. What is their combined mass?
10
Two stars in a binary system are determined from their position on the H-R diagram and the mass-luminosity relation to have a combined mass of 8Msun. Their orbital period, P, is 1 year. What is their orbital separation, a?
11
A line in a star's spectrum lies at 400.0 nanometers. In the laboratory, that same line lies at 400.2 nanometers. How fast is the star moving along the line of sight; that is, what is its radial velocity? Is it moving toward or away from us?
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