Astronomy
1st Edition
ISBN: 9781938168284
Author: Andrew Fraknoi; David Morrison; Sidney C. Wolff
Publisher: OpenStax
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Textbook Question
Chapter 19, Problem 18E
A 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?
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Using solar units, we find that a star has 4 times the luminosity of the Sun, a mass 1.25 times the mass of the Sun, and a surface temperature of 4090 K (take the Sun's surface temperature to be 5784 K for the sake of this problem). This means the star has a radius of.................... solar radii and is a .................... star (use the classification).
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.
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Chapter 19 Solutions
Astronomy
Ch. 19 - Explain how parallax measurements can be used to...Ch. 19 - Suppose you have discovered a new cepheid variable...Ch. 19 - Explain how you would use the spectrum of a star...Ch. 19 - Which method would you use to obtain the distance...Ch. 19 - What are the luminosity class and spectral type of...Ch. 19 - The meter was redefined as a reference to Earth,...Ch. 19 - While a meter is the fundamental unit of length,...Ch. 19 - Most distances in the Galaxy are measured in...Ch. 19 - The AU is defined as the average distance between...Ch. 19 - What would be the advantage of making parallax...
Ch. 19 - Parallaxes are measured in fractions of an...Ch. 19 - For centuries, astronomers wondered whether comets...Ch. 19 - The Sun is much closer to Earth than are the...Ch. 19 - Parallaxes of stars are sometimes measured...Ch. 19 - Estimating the luminosity class of an M star is...Ch. 19 - Figure 19.9 is the light curve for the prototype...Ch. 19 - Which of the following can you determine about a...Ch. 19 - A G2 star has a luminosity 100 times that of the...Ch. 19 - A star has a temperature of 10,000 K and a...Ch. 19 - What is the advantage of measuring a parallax...Ch. 19 - What is the disadvantage of the parallax method,...Ch. 19 - Luhman 16 and WISE 0720 are brown dwarfs, also...Ch. 19 - Most stars close to the Sun are red dwarfs. What...Ch. 19 - Why would it be easier to measure the...Ch. 19 - When Henrietta Leavitt discovered the...Ch. 19 - A radar astronomer who is new at the job claims...Ch. 19 - The New Horizons probe flew past Pluto in July...Ch. 19 - Estimate the maximum and minimum time it takes a...Ch. 19 - The Apollo program (not the lunar missions with...Ch. 19 - In 1974, the Arecibo Radio telescope in Puerto...Ch. 19 - Demonstrate that 1 pc equals 3.091013 k m and that...Ch. 19 - The best parallaxes obtained with Hipparcos have...Ch. 19 - Astronomers are always making comparisons between...Ch. 19 - Gaia will have greatly improved precision over the...Ch. 19 - Using the same techniques as used in Exercise...Ch. 19 - The human eye is capable of an angular resolution...Ch. 19 - How much better is the resolution of the Gaia...Ch. 19 - The most recently discovered system close to Earth...Ch. 19 - What would the parallax of Luhman 16 (see Exercise...Ch. 19 - The New Horizons probe that passed by Pluto during...Ch. 19 - What physical properties are different for an M...
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- Our Sun, a type G star, has a surface temperature of 5800 K. We know, therefore, that it is cooler than a type O star and hotter than a type M star. Given what you learned about the temperature ranges of these types of stars, how many times hotter than our Sun is the hottest type O star? How many times cooler than our Sun is the coolest type M star?arrow_forwardThe lowest mass for a true star is 1/12 the mass of the sun. What is the luminosity of this star (in units of the sun’s luminosity) based upon mass luminosity relationship? Use the exponent of 4 for easy calculations instead of 3.9arrow_forwardWhich of the following stars has the highest surface temperature? Treat the star as a blackbody. a)A dim red star b)A bright red star c)A bright orange star d)A dim orange star e)A bright yellow stararrow_forward
- The mass-luminosity relation describes the mathematical relationship between luminosity and mass for main sequence stars. It describes how a star with a mass of 4 M⊙ would have a luminosity of ______ L⊙. If a star has a radius 1/2 that of the Sun and a temperature 4 that of the Sun, how many times higher is the star's luminosity than that of the Sun? (If it is smaller by a factor of 8, you would write 0.125 because 1/8=0.125) If a star has a radius 2 times larger than the Sun's and a luminosity 1/4th that of the Sun, how many times higher is the star's temperature than that of the Sun? (If it is smaller by a factor of 8, you would write 0.125 because 1/8=0.125) If a star has a surface temperature 2 times lower than the Sun's and a luminosity the same as the Sun, how many times larger is the star than the Sun? (If it is smaller by a factor of 8, you would write 0.125 because 1/8=0.125)arrow_forwardIn a laboratory, the Balmer-beta spectral line of hydrogen has a wavelength of 486.1 nm . If the line appears in a star’s spectrum at 485.8 nm , what is the star’s radial velocity? Is it approaching or receding? Is this a blueshift or a redshift?arrow_forwardOne 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?arrow_forward
- If a star has a surface temperature of 3000 K but a luminosity 150 times greater than our Sun, what size is this star? Give your answer in units of the solar radius, R .arrow_forward= A star population is composed of stars with masses in the range between 1M and 150M. The initial mass function is = 0 (M/M)-2.3, where o (Mo). The luminosity of a star = (M/M) 3.3. Calculate the percentage of the total luminosity of the stars in the population which is produced by stars with mass between 120M and 150M. scales with its mass as L/Larrow_forward12: A star with spectral type A0 has a surface temperature of 9600 K and a radius of 2.2 RSun. How many times more luminous is this star than the Sun? (if it is less luminous enter a number less than one) Answer: 36.854 13:This star has a mass of 3.3 MSun. what is the main sequence lifetime of this star? You may assume that the lifetime of the sun is 1010 yr. Please answer question 13 thank you.arrow_forward
- If parallax of a star is 0.22 arc-seconds and its apparent brightness is 50 x 10-6 W/m2 . What is its luminosity? 2.5 x 1030 W 3.2 x 1026 W 1.2 x 1031 W 5.3 x 1034 Warrow_forwardMany 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?arrow_forwardIf a star has a surface temperature 2 times lower than the Sun's and a luminosity the same as the Sun, how many times larger is the star than the Sun? (If it is smaller by a factor of 8, you would write 0.125 because 1/8=0.125)arrow_forward
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