Foundations of Astronomy
13th Edition
ISBN: 9781305079151
Author: Michael A. Seeds, Dana Backman
Publisher: Cengage Learning
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Chapter 13, Problem 4RQ
To determine
The explanation for the evolution of white dwarf in the Milky Way Galaxy.
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A 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.
Assume that the mass of the core of a star that just went Supernova type II is $2.5 \mathrm{M}_{\odot}$ before and after the collapse, while the Radius changes from $10^3 \mathrm{~km}$, before the collapse, to 12 km , after the collapse respectively.(a) What is the change in potential energy of the core between the two stages before and after the collapse?(b) Knowing that the luminosity of the Sun is $4 \times 10^{26} \mathrm{~W}$ how many years would it take the Sun to release the same amount of energy?
For 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.)
Chapter 13 Solutions
Foundations of Astronomy
Ch. 13 - Prob. 1RQCh. 13 - Prob. 2RQCh. 13 - Prob. 3RQCh. 13 - Prob. 4RQCh. 13 - Prob. 5RQCh. 13 - Prob. 6RQCh. 13 - Prob. 7RQCh. 13 - Prob. 8RQCh. 13 - Prob. 9RQCh. 13 - Prob. 10RQ
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, physics and related others by exploring similar questions and additional content below.Similar questions
- Q7// a- Estimate the density of a white dwarf if it has a solar mass packed into a sphere with approximately 10² Ro b- For a white dwarf of density 1.0 x 10° g/cm3, and Z/A = 0.5, estimate the degeneracy pressure and compare it with the thermal pressure of a gas at a temperature of 1.0 x10' K.arrow_forwardQUESTION 16 Use the figure shown below to complete the following statement: A low-mass protostar (0.5 to 8M the mass compared to our sun) remains roughly constant in decreases in until it makes a turn towards the main sequence, as it follows its evolutionary track. Protostars of different masses follow diferent paths on their way to the main sequence. 107 Luminosity (L) 10 105 10 107 10² 101 1 10-1 10-2 10-3 Spectral type 0.01 R 0.001 Re 60 M MAIN SEQUENCE 40,000 30,000 20 Mau 10 Mgun 5 Mun 0.1 Run Ren radius; temperature luminosity; radius 3 Min. 05 BO temperature; luminosity Oluminosity: temperature radius: luminosity 1 M 10,000 6000 Surlace temperature (K) 1,000 Rs 2 M STAR L 0.8 M B5 AO FOGO КБ МБ -10 +10 3000 Absolute visual magnitude andarrow_forwardWhat determines the mass distribution of forming stars, the initial mass function (IMF)?arrow_forward
- We learned in class that, when stars collapse under their own gravity, they conserve angular momentum, which is proportional to mass times radius times rotational speed. Suppose the entire sun (radius 695,700 km) were to collapse to a neutron star with a radius of only 10 km. Before the collapse, the rotational speed at the equator = 2.0 km/s, and the rotational period is 25 days. Using the same steps that you used for the white dwarf calculations, calculate the final rotation period if the entire sun were to collapse to a 10 km radius neutron star. Give your answer in units of seconds. Answer: Checkarrow_forwardWhy is star formation more likely to occur in cold molecular clouds than in regions where the temperature of the interstellar medium is several hundred thousand degrees?arrow_forwardWhere in the Galaxy would you expect to find Type II supernovae, which are the explosions of massive stars that go through their lives very quickly? Where would you expect to find Type I supernovae, which involve the explosions of white dwarfs?arrow_forward
- According to the text, a star must be hotter than about 25,000 K to produce an H II region. Both the hottest white dwarfs and main-sequence O stars have temperatures hotter than 25,000 K. Which type of star can ionize more hydrogen? Why?arrow_forward1. A planetary nebula has an angular diameter of 76 arc seconds and a distance of 5100 ly. What is its linear diameter (in ly)? Hint: Use the small-angle formula: angular diameter (in arc seconds) 2.06 ✕ 105 = linear diameter distance 2. Suppose a planetary nebula is 3.2 pc in diameter, and Doppler shifts in its spectrum show that the planetary nebula is expanding at 31 km/s. How old is the planetary nebula in yr? (Note: 1 pc = 3.1 ✕ 1013 km and 1 yr = 3.2 ✕ 107 s.)arrow_forwardWhat is the ratio of the percent of metals in extreme Population I stars (3%) to that in extreme Population II stars (0.05%)? NpopI NpopII =arrow_forward
- 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 the mass of a star. You should assume that the luminosity is constant throughout a star's main sequence life time, and that the amount of mass converted into energy by a star while it is on the main sequence is given by AM main sequence life time of a 20 Solar mass star given that the Sun is expected to spend 1010 years on the main sequence. Comment on the significance of your answer. fM, where f is a constant. Estimate thearrow_forwardIn a star of 1 solar mass (M☉), the core hydrogen burning phase, also known as the main sequence phase, lasts for approximately 10 billion years. Suppose there's a star of 15 solar masses (M☉). Stars of higher mass burn through their hydrogen at a faster rate, following an approximate relation that the lifetime of a star on the main sequence (T) is proportional to its mass (M) raised to the power of -2.5 (T ∝ M^-2.5). Calculate approximately how long this 15 solar mass star would remain in the main sequence phase, compared to the 1 solar mass star.arrow_forwardFor the PP chain 0.7% of the mass participating in nuclear fusion is liberated as energy which produces a star's luminosity. Assume that the core of a main sequence star consists of 10% of its total mass. Hence, estimate the lifetime of a star on the main sequence in terms of its luminosity L/L. Give your answer in years. You may use the observed mass-luminosity relation L x M³.5, where M is the star's total mass. Using typical values, calculate estimates for the main sequence lifetime of a KO star and a 05 star. Describe briefly why your estimate might be more accurate for K stars compared to O stars.arrow_forward
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