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 17, Problem 36Q
To determine
(a)
The intensity curve of black body at a temperature of
To determine
(b)
The intensity curve of black body at a temperature of
To determine
(c)
The reason why color ratiogreater than 1 for very cool star and less than 1 for very hot star.
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Use Wien's Law to calculate the peak wavelength of light coming from the Sun. Assume T=5800 K for the surface temperature of the Sun. Wein's displacement law says that the blackbody temperature and peak wavelength multiplied together give a constant of 0.29 cm-K. (K is degrees Kelvin).
Convert the wavelength from part A into a frequency. The product of wavelength and frequency for electromagnetic radiation is a constant, the speed of light (c), 3 x 10^10 cm/s.
Calculate the Doppler linewidth for an emission line near 500 nm from Ni, at 3000 K.
Assuming stars to behave as black bodies stefan-boltzmann law to show that the luminosity of a star is related to its surface temperature and size in the following way:
L = 4(3.14)R^2oT^4
where o= 5.67 ×10^-8 Wm^-2 K-4 is the stefan- boltzmann constant. Then use this expression together with the knowledge that the sun has a surface temperature of 5700k and radius 695 500km to calculate the luminosity of the Sun in units of Watts
Chapter 17 Solutions
Universe: Stars And Galaxies
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- A)The star 58 Eridani is a feint but naked-eye star similar to the Sun. Suppose that you are observing this star in the night sky without a telescope. Ignoring any interstellar extinction or atmospheric absorption, approximately how many photons per second arrive at your retina? Show all steps in calculation . B) The Mid-infared Instrument (MIRI , camera and spectrograph ) on the James Webb Space Telescope operates in the band 5-28 µm . For 58 Eridani , approximatley how many photons per second can be used by this instrument ? Assume that MIRI takes all the photons from the full JWST mirror . Show all steps in calcultation . Describe breifly two or three other factors which play a role in determining the sensetivitu of an instrument such as MIRI ?arrow_forwardThe Stefan-Boltzmann equation can be used to estimate the size of asteroids. "Sigma," the Stefan-Boltzmann constant, is 5.67 x 10 Watts/m²K. If you want to abbreviate Plus 1.1415 You measure the infrared emission from an asteroid and conclude that it has a temperature of 249 K. Using rader you find the distance, and are then able to use your infrared brightness to determine a luminosity of 7.21E+12 Watts. If you assume the asteroid is roughly spherical, what is its radius in meters? CHECK ANSWERarrow_forwardImagine that you are observing a star and you find the wavelength of peak emission for the star to be 500 nm. What would the wavelength of peak emission be for a new star that has a surface temperature that is a third of the original star?arrow_forward
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