Universe: Stars And Galaxies
6th Edition
ISBN: 9781319115098
Author: Roger Freedman, Robert Geller, William J. Kaufmann
Publisher: W. H. Freeman
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Question
Chapter 17, Problem 33Q
To determine
(a)
The reason why given equation is correct.
To determine
(b)
The color indices for the Sun, Bellatrix and Betelgeuse.
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The origin of the above quote (with "flame" or "candle" sometimes substituted for "light") is unclear. It is often attributed to either Lao Tzu or to the character Eldon Tyrell from the 1982 movie Blade Runner.
Stars follow a similar law, although the factor isn't precisely 1/2. In this problem, you will figure out the precise factor that the quote should have to apply to stars.
Using the proportionality relationships for stellar luminosity as a function of mass and stellar lifetime as a function of mass, combine the two equations to arrive at a proportionality for stellar lifetime as a function of luminosity.
Consider a star with luminosity twice that of the Sun's. Compute the star's main sequence lifetime as a multiple of the Sun's main sequence lifetime. Enter your result below as a decimal. For example, if you found TT⊙=0.3, enter "0.3". (Here T is the star's lifetime and T⊙ is the Sun's main sequence lifetime.
As a star runs out of hydrogen to fuel nuclear fusion in its core, changes within the star usually cause it to leave the main sequence, expanding and cooling as it does so. Would a star with a radius 6 times that of the Sun, but a surface temperature 0.4 times that of the Sun, be more, or less luminous than the Sun?
Show and explain your reasoning.
You may assume the surface area of a sphere is A = 4πr2.
A star has a measured radial velocity of 100 km/s. If you measure the wavelength of a particular spectral line of Hydrogen as 486.42 nm, what was the laboratory wavelength (in nm) of the line? (Round your answer to at least one decimal place.)
Which spectral line does this likely correspond to?
Balmer-alpha (656.3 nm)
Balmer-beta (486.1 nm)
Balmer-gamma (434.0 nm)
Balmer-delta (410.2 nm)
Chapter 17 Solutions
Universe: Stars And Galaxies
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- The Hα spectral line has a rest wavelength of 6562.8 ˚A (remember: 1 ˚A = 10−10 m). In star A, the lineis seen at 6568.4 ˚A, in star B it’s seen at 6560.3 ˚A, and in star C it’s seen at 6562.8 ˚A. Which star ismoving the fastest (along the line of sight) and what is the radial velocity of each star?arrow_forwardA star has a measured radial velocity of 300 km/s. If you measure the wavelength of a particular spectral line of Hydrogen as 657.18 nm, what was the laboratory wavelength (in nm) of the line? (Round your answer to at least one decimal place.) nm Which spectral line does this likely correspond to? Balmer-alpha (656.3 nm) Balmer-beta (486.1 nm) Balmer-gamma (434.0 nm) Balmer-del ta (410.2 nm)arrow_forwardTwo stars (a and b) in a binary system have apparent V-band magnitudes of 8.0 and 8.4 mag, and B-V colour indices of 0.3 and -0.5 mag, respectively. (a) Which star is brightest in the V-band? (b) Which star is brightest in the B-band? (c) Which star would appeal bluer to the naked eye? (d) What is the ratio of monochromatic fluxes of the stars in the B-band? (e) What is the total apparent magnitude of the system in the V-band (assuming it is unresolved)?arrow_forward
- The figure below shows the spectra of two stars on the same scale (Star A = red line; Star B = green line). The three strongest (deepest) absorption lines in each spectrum are due to the same element (they are marked with arrows in the Star A spectrum). How does the radial velocity of Star B compare to the radial velocity of Star A? (Choose the most correct answer; assume both spectra were taken from Earth.) Normalized flux 1.1 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 882 882.5 883 883.5 884 Star A Star B 884.5 885 Wavelength (nm) Star B is moving away from the Earth faster than Star A. Star A and Star B are both moving away from the Earth with the same radial velocity. Star B is moving towards the Earth faster than Star A. Star A and Star B are both moving towards the Earth with the same radial velocity.arrow_forwardTwo stars are identified on the Hertzsprung-Russell diagram below. Hertzsprung-Russell Diagram Temperature (K) 40,000 20,00010,000 7,500 5,500 4,500 3,000 10 10 10 www 10 10 B. G K M Spectral Class Based on this diagram, how do the characteristics of Star 1 and Star 2 compare? Star 1 is cooler and less bright than Star 2. O Star 1 is hotter and brighter than Star 2. O Star 1 is cooler and brighter than Star 2. O Star 1 is hotter and less bright than Star 2. O Aisoujunarrow_forwardA star has a parallax angle of 0.0270 arcseconds and an apparent magnitude of 4.641. The distance to this star is 37.03 parsecs and the absolute magintude is 1.79. 18: What is the luminosity of this star? (HINT: The luminosity of the Sun is 3.85×1026 W.) Using the Forumla M1 - M2 = -2.5 log(L1/L2) the absolute magnitude of the Sun is 4.8arrow_forward
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