Astronomy
1st Edition
ISBN: 9781938168284
Author: Andrew Fraknoi; David Morrison; Sidney C. Wolff
Publisher: OpenStax
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Textbook Question
Chapter 23, Problem 41E
One way to calculate the radius of a star is to use its luminosity and temperature and assume that the star radiates approximately like a blackbody. Astronomers have measured the characteristics of central stars of planetary nebulae and have found that a typical central star is 16 times as luminous and 20 times as hot (about 110,000 K) as the Sun. Find the radius in terms of the Sun’s. How does this radius compare with that of a typical white dwarf?
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One way to calculate the radius of a star is to use its luminosity and temperature and assume that the star radiates approximately like a blackbody. Astronomers have measured the characteristics of central stars of planetary nebulae and have found that a typical central star is 16 times as luminous and 20 times as hot (about 110,000 K) as the Sun. Find the radius in terms of the Sun’s. How does this radius compare with that of a typical white dwarf?
A main sequence star of mass, M, and radius, R, collapses to a white dwarf star with a radius 1.0% as big as the original star. If ω is the angular velocity of the original star, what is the angular velocity of the white dwarf star? Approximate the star to be a uniform solid sphere.
a.
20,000ω
b.
10,000ω
c.
50,000ω
d.
1,000ω
e.
5,000ω
Use
t =
1
M2.5
to compute the life expectancy of a 0.6-solar-mass star. (A solar lifetime is approximately 10 billion years.) yrWhy might this be an underestimate if the star is fully mixed by convection?
a) If the star is fully mixed its mass will be much larger than 0.6 solar masses.
b) If the star is fully mixed its mass will be much smaller than 0.6 solar masses.
c) If the star is fully mixed it will be able to use a larger portion of its hydrogen in fusion than the Sun.
d) If the star is fully mixed it will be able to use a smaller portion of its hydrogen in fusion than the Sun.
Chapter 23 Solutions
Astronomy
Ch. 23 - How does a white dwarf differ from a neutron star?...Ch. 23 - Describe the evolution of a star with a mass like...Ch. 23 - Describe the evolution of a massive star (say, 20...Ch. 23 - How do the two types of supernovae discussed in...Ch. 23 - A star begins its life with a mass of 5 MSunbut...Ch. 23 - If the formation of a neutron star leads to a...Ch. 23 - How can the Crab Nebula shine with the energy of...Ch. 23 - How is a nova different from a type Ia supernova?...Ch. 23 - Apart from the masses, how are binary systems with...Ch. 23 - What observations from SN 1987A helped confirm...
Ch. 23 - Describe the evolution of a white dwarf over time,...Ch. 23 - Describe the evolution of a pulsar over time, in...Ch. 23 - How would a white dwarf that formed from a star...Ch. 23 - What do astronomers think are the causes of...Ch. 23 - How did astronomers finally solve the mystery of...Ch. 23 - Arrange the following stars in order of their...Ch. 23 - Would you expect to find any white dwarfs in the...Ch. 23 - Suppose no stars more massive than about 2 MSunhad...Ch. 23 - Would you be more likely to observe a type II...Ch. 23 - Astronomers believe there are something like 100...Ch. 23 - Would you expect to observe every supernova in our...Ch. 23 - The Large Magellanic Cloud has about one-tenth the...Ch. 23 - Look at the list of the nearest stars in Appendix...Ch. 23 - If most stars become white dwarfs at the ends of...Ch. 23 - If a 3 and 8 MSunstar formed together in a binary...Ch. 23 - You have discovered two star clusters. The first...Ch. 23 - A supernova remnant was recently discovered and...Ch. 23 - Based upon the evolution of stars, place the...Ch. 23 - What observations or types of telescopes would you...Ch. 23 - How would the spectra of a type II supernova be...Ch. 23 - The ring around SN 1987A (Figure 23.12) initially...Ch. 23 - What is the acceleration of gravity (g) at the...Ch. 23 - What is the escape velocity from the Sun? How much...Ch. 23 - What is the average density of the Sun? How does...Ch. 23 - Say that a particular white dwarf has the mass of...Ch. 23 - What is the escape velocity from the white dwarf...Ch. 23 - What is the average density of the white dwarf in...Ch. 23 - Now take a neutron star that has twice the mass of...Ch. 23 - What is the escape velocity from the neutron star...Ch. 23 - What is the average density of the neutron star in...Ch. 23 - One way to calculate the radius of a star is to...Ch. 23 - According to a model described in the text, a...Ch. 23 - Do the same calculations as in Exercise 23.42 but...Ch. 23 - If the Sun were replaced by a white dwarf with a...Ch. 23 - A supernova can eject material at a velocity of...Ch. 23 - A supernova remnant was observed in 2007 to be...Ch. 23 - The ring around SN 1987A (Figure 23.12) started...Ch. 23 - Before the star that became SN 1987A exploded, it...Ch. 23 - What is the radius of the progenitor star that...Ch. 23 - What is the acceleration of gravity at the surface...Ch. 23 - What was the escape velocity from the surface of...Ch. 23 - What was the average density of the star that...Ch. 23 - If the pulsar shown in Figure 23.16 is rotating...
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- What observations or types of telescopes would you use to distinguish a binary system that includes a main-sequence star and a white dwarf star from one containing a main-sequence star and a neutron star?arrow_forwardA G2 star has a luminosity 100 times that of the Sun. What kind of star is it? How does its radius compare with that of the Sun?arrow_forwardWhat is the radius of the progenitor star that became SN 1987A? Its luminosity was 100,000 times that of the Sun, and it had a surface temperature of 16,000 K.arrow_forward
- What physical properties are different for an M giant with a luminosity of 1000 LSunand an M dwarf with a luminosity of 0.5 LSun? What physical properties are the same?arrow_forwardA star begins its life with a mass of 5 MSunbut ends its life as a white dwarf with a mass of 0.8 MSun. List the stages in the star’s life during which it most likely lost some of the mass it started with. How did mass loss occur in each stage?arrow_forwardHow much would you weigh if you were suddenly transported to the white dwarf Sirius B? You may use your own weight (or if don’t want to own up to what it is, assume you weigh 70 kg or 150 lb). In this case, assume that the companion to Sirius has a mass equal to that of the Sun and a radius equal to that of Earth. Remember Newton’s law of gravity: F=GM1M2/R2 and that your weight is proportional to the force that you feel. What kind of star should you travel to if you want to lose weight (and not gain it)?arrow_forward
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