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 45Q
To determine
Whether a galaxy having a set recessional velocity is closer to or farther away from us when compared to the distance in a universe that is expanding at steady rate.
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If a galaxy is 8.9 Mpc away from Earth and recedes at 497 km/s, what is H. (in km/s/Mpc)?
km/s/Mрс
What is the Hubble time (in yr)?
years
How old (in yr) would the universe be, assuming space-time is flat and the expansion of the universe has not been accelerating?
years
How would acceleration change your answer?
If the expansion of the Universe has been accelerating, the Universe could be substantially younger than the value entered above.
If the expansion of the Universe has been accelerating, the Universe could be substantially older than the value entered above.
The background radiation has an average temperature of 2.7 K, using Wien’s Law, the current background radiation in the microwave region, the peak wavelength is 1mm. In the past, when the cosmic background radiation had a peak wavelength of 51.1 µm, calculate the relative size of the universe compared to the current size of the universe, that is, the universe was how much smaller by a factor of what?
Round to TWO places past the decimal
If most galaxies are moving away from us, are we at the center of the universe? Why or why not?
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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- What is the evidence that the Universe was homogeneous during its first 400,000 years?arrow_forwardAssume a flat Friedmann-Robertson-Walker universe.Calculate the redshift z at which the temperature of the CMB was T = 10 T0, where T0 is thetemperature of the CMB today. Assuming the universe was matter dominated throughout itsevolution, calculate the time at which T = 10 T0 in Gigayears.arrow_forwardAssume a flat FRW universe, dominated by radiation throughout its history. Calculate the physical, cosmological horizon size at t=t_0 The initial conditions for the scale factor are a=a_0 at t=t0(today). Which asnwer is correct; a)R_H=2a_0ct_0 b) R_H = 3a_0ct_0 c)R_H = ct_0 d) R_H=2ct_0arrow_forward
- If you observe light emitted from a distance object when the cosmic background temperature was Tz=54K, what is the redshift z of that light? At that redshift, what was the diameter Dz of the universe at that time compared to the diameter of today's universe D0?arrow_forwardCalculate the Hubble time for a universe with a Hubble constant of sixty kilometers per second per megaparsec.arrow_forwardIf a galaxy is 8.8 Mpc away from Earth and recedes at 498 km/s, what is H0 (in km/s/Mpc)? _______ km/s/Mpc What is the Hubble time (in yr)? _______ yr How would acceleration change your answer? A: If the expansion of the Universe has been accelerating, the Universe could be substantially younger than the value entered above. B: If the expansion of the Universe has been accelerating, the Universe could be substantially older than the value entered above.arrow_forward
- How do we know andromeda galaxy is moving towards us?arrow_forwardWhat is the difference between, (a)Sa and Sb galaxy, (b) between and S0 and an Sa galaxy, (c) between Sb and SBb galaxy, (d) between an E7 and E0 galaxy.arrow_forwardWhat Hubble constant corresponds to an approximate age of the universe of 1010 y? To get an approximate value, assume the expansion rate is constant and calculate the speed at which two galaxies must move apart to be separated by 1 Mly (present average galactic separation) in a time of 1010 yarrow_forward
- Calculate the critical density necessary for a closed universe for two extremes of the Hubble constant: 64 km . s-1 . Mpc-1 and 78 km . s-1 . Mpc-1.arrow_forwardThe matter density in the Universe today is ?m=2.7×10−27kgm−3. What would be the value of the density parameter, Ω0, if the Hubble constant had the value H0 = 38 km/s/Mpc?arrow_forwardThe present number density of electrons in the Universe is the same as that of protons, about 0.2 m-3. Consider a time long before the formation of the microwave background, when the scale factor was x times smaller than its present value. What was the number density of electrons then? Value: x = 12×106arrow_forward
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