Foundations of Astronomy (MindTap Course List)
14th Edition
ISBN: 9781337399920
Author: Michael A. Seeds, Dana Backman
Publisher: Cengage Learning
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Chapter 13, Problem 1P
To determine
The life expectancy of a
The reason behind that life expectancy value will be an underestimate if the star is fully mixed.
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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.
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.)
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 the
Chapter 13 Solutions
Foundations of Astronomy (MindTap Course List)
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
Ch. 13 - Prob. 11RQCh. 13 - Prob. 12RQCh. 13 - Prob. 13RQCh. 13 - Prob. 14RQCh. 13 - Prob. 15RQCh. 13 - Prob. 16RQCh. 13 - Prob. 17RQCh. 13 - Prob. 18RQCh. 13 - Prob. 19RQCh. 13 - Prob. 20RQCh. 13 - Prob. 21RQCh. 13 - Prob. 22RQCh. 13 - Prob. 23RQCh. 13 - Prob. 24RQCh. 13 - Prob. 25RQCh. 13 - Prob. 1PCh. 13 - Prob. 2PCh. 13 - Prob. 3PCh. 13 - Prob. 4PCh. 13 - Prob. 5PCh. 13 - Prob. 6PCh. 13 - Prob. 7PCh. 13 - Prob. 8PCh. 13 - Add a fourth column to Table 13-1 and write in the...Ch. 13 - Prob. 10PCh. 13 - Prob. 11PCh. 13 - Prob. 12PCh. 13 - Prob. 13PCh. 13 - Prob. 14PCh. 13 - Prob. 15PCh. 13 - Prob. 2SOPCh. 13 - Prob. 1LTLCh. 13 - Prob. 2LTLCh. 13 - Prob. 3LTLCh. 13 - Prob. 4LTLCh. 13 - Prob. 5LTL
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- Using the HR diagram what is the approximate range of relative luminosities covered for a main sequence star at 10 000 K?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_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
- 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_forwardUse the provided equation of hydrostatic equilibrium to estimate the central pressure in the Sun. Repeat the process for a main sequence star that has a mass of 2M⨀. (Hint: use the known approximation that r ~ M for all main sequence stars to find the radius and new average density of the main sequence star)arrow_forwardThe Orion Nebula is a gas-rich region in which stars are being born. The nebula is at a distance of about 1344 lyr from Earth.Suppose you observe a star in the Orion Nebula to have an apparent magnitude of 6.75. Calculate the absolute magnitudeof the star. Also calculate the luminosity of the star in units of the solar luminosity (knowing that the absolute magnitude ofthe Sun is 4.8).arrow_forward
- If a 100 solar mass star were to have a luminosity of 107 times the Sun’s luminosity, how would such a star’s density compare when it is on the main sequence as an O-type star, and when it is a cool supergiant (M-type)? Use values of temperature from Figure 18.14 or Figure 18.15 and the relationship between luminosity, radius, and temperature as given in Exercise 18.47. Figure 18.15 Schematic HR Diagram for Many Stars. Ninety percent of all stars on such a diagram fall along a narrow band called the main sequence. A minority of stars are found in the upper right; they are both cool (and hence red) and bright, and must be giants. Some stars fall in the lower left of the diagram; they are both hot and dim, and must be white dwarfs. Figure 18.14 HR Diagram for a Selected Sample of Stars. In such diagrams, luminosity is plotted along the vertical axis. Along the horizontal axis, we can plot either temperature or spectral type (also sometimes called spectral class). Several of the brightest stars are identified by name. Most stars fall on the main sequence.arrow_forwardA supernova can eject material at a velocity of 10,000 km/s. How long would it take a supernova remnant to expand to a radius of 1 AU? How long would it take to expand to a radius of 1 light-years? Assume that the expansion velocity remains constant and use the relationship: expansiontime=distanceexpansionvelocity .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
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