Universe: Stars And Galaxies
6th Edition
ISBN: 9781319115098
Author: Roger Freedman, Robert Geller, William J. Kaufmann
Publisher: W. H. Freeman
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Chapter 20, Problem 2Q
To determine
The reason for horizontal branch-stars to be referred as Helium main-sequence stars.
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Observations show that stellar luminosity, L, and mass, M, are related by L x M3.5 for
main sequence stars. Obtain an expression that relates the main sequence life time and
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main sequence life time of a 20 Solar mass star given that the Sun is expected to spend
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=
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scales with its mass as L/L
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Chapter 20 Solutions
Universe: Stars And Galaxies
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- Question 41 .Suppose you are looking at H-R diagrams of two similar star clusters. The most luminous main sequence stars in the Porcini cluster are much more luminous than the most luminous main sequence stars in the Morel cluster. What can you conclude? O the Porcini cluster is younger than the Morel cluster O the Porcini cluster is farther away than the Morel cluster O the Porcini cluster is lower in metallicity than the Morel cluster O the Porcini cluster is larger in diameter than the Morel clusterarrow_forwardUsing 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).arrow_forwardA star population is composed of stars with masses in the range between 1M and 150M. The initial mass function is = (M/M)-2.3, where = (Mo). The luminosity of a star scales with its mass as L/L = (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.arrow_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_forwardFor a main sequence star with luminosity L, how many kilograms of hydrogen is being converted into helium per second? Use the formula that you derive to estimate the mass of hydrogen atoms that are converted into helium in the interior of the sun (LSun = 3.9 x 1026 W). (Note: the mass of a hydrogen atom is 1 mproton and the mass of a helium atom is 3.97 mproton. You need four hydrogen nuclei to form one helium nucleus.)arrow_forwardA main sequence star of mass 25 M⊙has a luminosity of approximately 80,000 L⊙. a. At what rate DOES MASS VANISH as H is fused to He in the star’s core? Note: When we say “mass vanish '' what we really mean is “gets converted into energy and leaves the star as light”. Note: approximate answer: 3.55 E14 kg/s b. At what rate is H converted into He? To do this you need to take into account that for every kg of hydrogen burned, only 0.7% gets converted into energy while the rest turns into helium. Approximate answer = 5E16 kg/s c. Assuming that only the 10% of the star’s mass in the central regions will get hot enough for fusion, calculate the main sequence lifetime of the star. Put your answer in years, and compare it to the lifetime of the Sun. It should be much, much shorter. Approximate answer: 30 million years.arrow_forward
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- a) A star has a temperature T = 15000K, mass M = 0.25M⊙ and luminosity L = 0.02L⊙. Sketch the position of this star on the Hertzsprung-Russell diagram relative to the main sequence.arrow_forwardStars found on the main sequence of a Hertzsprung-Russell diagram share certain features not shared by other stars. What are these features? A Stars on the main sequence of the Hertzsprung-Russell diagram are all roughly the same radius. Stars on the main sequence of a Hertzsprung-Russell diagram do not produce heavy elements like iron. Stars on the main sequence of the Hertzsprung-Russell diagram have an orderly arrangement of stellar masses, decreasing in mass from lower right to upper left. Stars on the Hertzsprung-Russell diagram main sequence have roughly the same age. Stars on the main sequence of a Hertzsprung-Russell diagram all generate energy from nuclear fusion. B D E F) None of the mentioned choices. 4arrow_forwardThe Hertzsprung-Russell diagram contains a region called the main sequence. Stars on this sequence have specific characteristics not found in other stars. What are these characteristics? a.Stars on the Hertzsprung-Russell diagram main sequence have roughly the same age. b.Stars on the main sequence of the Hertzsprung-Russell diagram are all roughly the same radius. c.Stars on the main sequence of the Hertzsprung-Russell diagram have an orderly arrangement of stellar masses, decreasing in mass from lower right to upper left. d.Stars on the main sequence of a Hertzsprung-Russell diagram do not produce heavy elements like iron. e.Stars on the main sequence of a Hertzsprung-Russell diagram all generate energy from nuclear fusion. f.None of the mentioned choices. Aristotle was a great Greek philosopher with many amazing ideas. Which of these statements about him is not true? a.Many of his claims about physics and astronomy were wrong. b.He was the first person to recognize…arrow_forward
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