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 25, Problem 25Q
To determine
The cosmic background
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2.90 x 106 nm : K
Find the wavelength (in mm) of maximum intensity of the cosmic microwave background radiation observed today. ( Hint: Use Wien's law, Amay
mm
What band of the electromagnetic spectrum is that in? (Examine the figure.)
Visible light
Short wavelengths
Long wavelengths
4 x 107 5x 107 6x 107 7x 10meters
(400 nm) (500 nm) (600 nm) /(700 nm)
Wavelength (meters)
10 12
10 10
10
104
102
1
102
104
Gamma-
Micro-
Ultra-
violet
X-ray
Infrared
Radio
ray
wave
UHF VHF FM
AM
Opaque
Visual
window
Radio
window
Transparent
Short
Wavelength
Long
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O microwave
O gamma ray
O ultraviolet
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Opacity of
Earth's atmosphere
You record the spectrum of a distant star using a telescope on the ground on Earth. Upon
analysing the spectrum, you discover absorption lines spaced at intervals typical of oxygen
atoms. Which of the following are possible interpretations of this evidence? Select all that
apply.
The width of the spectral lines gives the diameter of the star
The star is likely orbited by habitable planets with breathable atmospheres.
The height of the spectral lines above the star's general blackbody spectral curve tells us how much
oxygen is in the star
The atmosphere of Earth contains oxygen
The red or blueshift of the set of lines can tell us the speed of the star's motion toward or away from us
Astronomers can determine the heat of various areas of the universe by making observations about energy they emit. Gamma rays can be found in areas where there is a lot of star formation occurring.
What would you guess about the temperature of these areas? Explain why.Do you think there would be a lot of particles present? Explain why.
Chapter 25 Solutions
Universe: Stars And Galaxies
Ch. 25 - Prob. 1QCh. 25 - Prob. 2QCh. 25 - Prob. 3QCh. 25 - Prob. 4QCh. 25 - Prob. 5QCh. 25 - Prob. 6QCh. 25 - Prob. 7QCh. 25 - Prob. 8QCh. 25 - Prob. 9QCh. 25 - Prob. 10Q
Ch. 25 - Prob. 11QCh. 25 - Prob. 12QCh. 25 - Prob. 13QCh. 25 - Prob. 14QCh. 25 - Prob. 15QCh. 25 - Prob. 16QCh. 25 - Prob. 17QCh. 25 - Prob. 18QCh. 25 - Prob. 19QCh. 25 - Prob. 20QCh. 25 - Prob. 21QCh. 25 - Prob. 22QCh. 25 - Prob. 23QCh. 25 - Prob. 24QCh. 25 - Prob. 25QCh. 25 - Prob. 26QCh. 25 - Prob. 27QCh. 25 - Prob. 28QCh. 25 - Prob. 29QCh. 25 - Prob. 30QCh. 25 - Prob. 31QCh. 25 - Prob. 32QCh. 25 - Prob. 33QCh. 25 - Prob. 34QCh. 25 - Prob. 35QCh. 25 - Prob. 36QCh. 25 - Prob. 37QCh. 25 - Prob. 38QCh. 25 - Prob. 39QCh. 25 - Prob. 40QCh. 25 - Prob. 41QCh. 25 - Prob. 42QCh. 25 - Prob. 43QCh. 25 - Prob. 44QCh. 25 - Prob. 45QCh. 25 - Prob. 46QCh. 25 - Prob. 47QCh. 25 - Prob. 48QCh. 25 - Prob. 49QCh. 25 - Prob. 50QCh. 25 - Prob. 51QCh. 25 - Prob. 52QCh. 25 - Prob. 53QCh. 25 - Prob. 54QCh. 25 - Prob. 55Q
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- Would you expect to be able to detect an H II region in X-ray emission? Why or why not? (Hint: You might apply Wien’s law)arrow_forwardExplain how emission lines and absorption lines are formed. In what sorts of cosmic objects would you expect to see each?arrow_forwardEven though neutral hydrogen is the most abundant element in interstellar matter, it was detected first with a radio telescope, not a visible light telescope. Explain why. (The explanation given in Analyzing Starlight for the fact that hydrogen lines are not strong in stars of all temperatures may be helpful.)arrow_forward
- Why would we not expect to detect X-rays from a disk of matter about an ordinary star?arrow_forwardWhy is it difficult to determine where cosmic rays come from?arrow_forwardThe Andromeda Galaxy, M31, is the closest large spiral galaxy to our Milky Way. When we look at its chemical spectrum, we see that its hydrogen alpha emission line (Hα) has an observed wavelength of λobs = 655 nm.-Calculate z, being careful with the sign.-How fast is it moving in km/s?-Is it redshifted or blueshifted? Is it moving towards or away from us? answer to three significant figures.arrow_forward
- At the low temperature found in some interstellar molecular clouds (around 100 K), molecular oxygen emission is strongest at a wavelength of 0.2521 cm. Determine the speed (in km/s) of a low temperature molecular cloud containing molecular oxygen if its strongest emission is at a wavelength of 0.1885 cm. Note that this cloud is moving towards us, so the answer should be negative.arrow_forwardA)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_forwardWhat is background radiation? Why is it important to determine the back-ground radiation for the effect of different distances?arrow_forward
- 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 Wattsarrow_forwardImagine that you are observing the light from a distant star that is located in a galaxy 100 million lightyears away from you. By analysis of the starlight received, you are able to tell that the image we see is of a 10- million-year-old star. You are also able to predict that the star will have a total lifetime of 50 million years, at which point it will end in a catastrophic supernova. a) How old does the star appear to be to us here on Earth now? b) How long will it be before we receive the light from the supernova event? c) Has the supernova already occurred? If so, when did it occur?arrow_forwardA planetary nebula is visible due to ____.a. blackbody continuum radiation from the interstellar mediumb. line emission from the interstellar mediumc. scattering from dust grains ejected by a dying stard. blackbody continuum radiation from a hot gas ejected by a dying stare. line emission from ionized hydrogen gas ejected by a dying star My guess is E. Please help me understand why I am wrong if so.arrow_forward
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