21st Century Astronomy
6th Edition
ISBN: 9780393428063
Author: Kay
Publisher: NORTON
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Chapter 16, Problem 35QP
To determine
The luminosity for the stars.
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Finally estimate the lifetime of an M0 spectral type star if the total mass of the star is M = 0.51M⊙ , and it has a total luminosity L = 7.7× 10−2L⊙. Make the same assumptions as the previous two problems. How does your calculated Main Sequence lifetime for the M0 type star compare to the Main Sequence lifetime you calculated for the Sun?
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.
Suppose a protostar has a luminosity of
157,341
Lo
and a surface temperature of 4,540 K
(Kelvins). What is the radius of this
protostar?
[Enter your answer as a multiple of the
Sun's radius. I.e., if you find R = 20
Ro
enter 20. This problem is easier if you
start with the relevant equation and
create a ratio using the Sun's values.
Recall that the Sun has a surface
temperature of 5778 K. ]
Chapter 16 Solutions
21st Century Astronomy
Ch. 16.1 - Prob. 16.1CYUCh. 16.3 - Prob. 16.3CYUCh. 16.4 - Prob. 16.4CYUCh. 16.5 - Prob. 16.5CYUCh. 16 - Prob. 1QPCh. 16 - Prob. 2QPCh. 16 - Prob. 3QPCh. 16 - Prob. 4QPCh. 16 - Prob. 5QPCh. 16 - Prob. 6QP
Ch. 16 - Prob. 8QPCh. 16 - Prob. 9QPCh. 16 - Prob. 10QPCh. 16 - Prob. 11QPCh. 16 - Prob. 12QPCh. 16 - Prob. 13QPCh. 16 - Prob. 14QPCh. 16 - Prob. 15QPCh. 16 - Prob. 16QPCh. 16 - Prob. 17QPCh. 16 - Prob. 18QPCh. 16 - Prob. 19QPCh. 16 - Prob. 20QPCh. 16 - Prob. 21QPCh. 16 - Prob. 23QPCh. 16 - Prob. 24QPCh. 16 - Prob. 25QPCh. 16 - Prob. 26QPCh. 16 - Prob. 27QPCh. 16 - Prob. 28QPCh. 16 - Prob. 29QPCh. 16 - Prob. 30QPCh. 16 - Prob. 31QPCh. 16 - Prob. 32QPCh. 16 - Prob. 33QPCh. 16 - Prob. 34QPCh. 16 - Prob. 35QPCh. 16 - Prob. 36QPCh. 16 - Prob. 37QPCh. 16 - Prob. 38QPCh. 16 - Prob. 39QPCh. 16 - Prob. 40QPCh. 16 - Prob. 41QPCh. 16 - Prob. 42QPCh. 16 - Prob. 43QPCh. 16 - Prob. 44QPCh. 16 - Prob. 45QP
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- 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) This star has a mass of 3.3 MSun. Using the simple approximation that we made in class, what is the main sequence lifetime of this star? You may assume that the lifetime of the sun is 1010 yr. Compare this to the lifetime of a A0 star listed in Table 22.1 (computed using a more sophisticated approach). Is the value you calculated in the previous problem longer or shorter than what is reported in the table? (L for longer, S for shorter) (You only get one try at this problem.)arrow_forwardA 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) 36.854 This star has a mass of 3.3 MSun. Using the simple approximation that we made in class, what is the main sequence lifetime of this star? You may assume that the lifetime of the sun is 1010 yr.arrow_forwardA 46M Sun main sequence star loses 1 Msun of mass over 105 years. (Due to the nature of this problem, do not use rounded intermediate values in your calculations including answers submitted in WebAssign.) How many solar masses did it lose in a year? By how much will its luminosity decrease if this mass loss continues over 0.8 million years? Due to the nature of this problem, for all parts, do not use rounded intermediate values in your calculations-including answers submitted in WebAssign. To determine the number of solar masses lost per year, divide the mass lost by the number of years over which it was lost. Mlost tlost-yr Part 1 of 3 dM = dM = MSun/yrarrow_forward
- 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).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_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_forward
- calculate the main sequence lifetime of (a) a 4M☉ star, and (b) a 0.75M☉ star. Express the lifetimes of these stars as multiples of the Sun's lifetime(t☉=10^10years), as well as in units of years.arrow_forwardIf a neutron Star has a radius of 12 km and a temperature of 8.0 x 10^6 K, how luminous is it? Express your answer in watts and also in solar luminosity units. (Hint: Use the relation L/L= (R/R)^2(T/T)^4 . Use 5,800 K for the surface temperature of the Sun. The luminosity of the sun is 3.83 x 10^26W) luminosity in watts ________ W luminosity in solar luminosity units ______ 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
- 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.arrow_forwardUsing the HR diagram what is the approximate range of relative luminosities covered for a main sequence star at 10 000 K?arrow_forwardObservations 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_forward
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