Astronomy
1st Edition
ISBN: 9781938168284
Author: Andrew Fraknoi; David Morrison; Sidney C. Wolff
Publisher: OpenStax
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Textbook Question
Chapter 27, Problem 20E
Show that no matter how big a redshift (z) we measure, v/c will never be greater than 1. (In other words, no galaxy we observe can be moving away faster than the
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Students have asked these similar questions
The most distant quasar is "J0313-1806". Its
redshift is z = 7.64.
[ z = (femitted - fobserved)/ fobserved]
Assume that the redshift is due to relative
motion. Then how fast is the quasar moving
away from Earth?
(speed as the fraction of c = )
| .704
According to Hubble's Law, the distance (r)
depends on the speed of recession (v)
according to v = Hor where Ho~
20km/s
Mly
How many years are required for light to
travel from the quasar to Earth?
(years = )
Two distant galaxies are observed to have redshifts z1 = 0.05 and z2 = 0.15, and distances d1 = 220.60 Mpc and d2 = 661.75 Mpc, respectively. Assuming the motion of the galaxies is due to the Hubble flow, determine the value of the Hubble constant, H0. Show how the value of H0 can be used to estimate the age of the Universe, describing any assumptions that you make. Use the value of H0 you have obtained to estimate the age of the Universe, expressing your answer in Gyr.
If p = 2.7 x 10-27 kgm-3, what is the radius of curvature R, of Einstein's static universe? How
long would it take a photon to circumnavigate such a universe?
Chapter 27 Solutions
Astronomy
Ch. 27 - Describe some differences between quasars and...Ch. 27 - Describe the arguments supporting the idea that...Ch. 27 - In what ways are active galaxies like quasars but...Ch. 27 - Why could the concentration of matter at the...Ch. 27 - Describe the process by which the action of a...Ch. 27 - Describe the observations that convinced...Ch. 27 - Why do astronomers believe that quasars represent...Ch. 27 - Why were quasars and active galaxies not initially...Ch. 27 - What do we now understand to be the primary...Ch. 27 - What is the typical structure we observe in a...
Ch. 27 - What evidence do we have that the luminous central...Ch. 27 - Suppose you observe a star-like object in the sky....Ch. 27 - Why don’t any of the methods for establishing...Ch. 27 - One of the early hypotheses to explain the high...Ch. 27 - A friend of yours who has watched many Star Trek...Ch. 27 - Could the Milky Way ever become an active galaxy?...Ch. 27 - Why are quasars generally so much more luminous...Ch. 27 - Suppose we detect a powerful radio source with a...Ch. 27 - A friend tries to convince you that she can easily...Ch. 27 - Show that no matter how big a redshift (z) we...Ch. 27 - If a quasar has a redshift of 3.3, at what...Ch. 27 - If a quasar is moving away from us at v/c=0.8 ,...Ch. 27 - In the chapter, we discussed that the largest...Ch. 27 - Rapid variability in quasars indicates that the...Ch. 27 - Large redshifts move the positions of spectral...Ch. 27 - Once again in this chapter, we see the use of...Ch. 27 - In the Check Your Learning section of Example...Ch. 27 - In the Check Your Learning section of Example...Ch. 27 - The quasar that appears the brightest in our sky,...
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, physics and related others by exploring similar questions and additional content below.Similar questions
- In the Check Your Learning section of Example 27.1, you were told that several lines of hydrogen absorption in the visible spectrum have rest wavelengths of 410 nm, 434 nm, 486 nm, and 656 nm. In a spectrum of a distant galaxy, these same lines are observed to have wavelengths of 492 nm, 521 nm, 583 nm, and 787 nm, respectively. The example demonstrated that z=0.20 for the 410 nm line. Show that you will obtain the same redshift regardless of which absorption line you measure.arrow_forwardThe temperature of the CMB today is T=2.725 K. Calculate the temperature of the CMB at redshift z=2000. Choose the option below that most closely matches your answer. Select one: O a. 9759 K O b. 3412 K Ос. 5453 K. O d. 5450K Ое. 2000 Кarrow_forwardConsider the following line element, ds² = -dt² + a² (t) (dx² + dy²) + b²(t) dz², where a(t) and b(t) are distinct functions. State whether or not this line element obeys the Cosmological Principle, if applied to describe the universe on large scales. Justify your answer.arrow_forward
- Given an object is receding from Earth at v=20(10^3)km x s^-1, Calculate its redshift z?arrow_forwardUse the Friedmann equations to show that the deceleration parameter go and the density parameter 2 are related through qo = 2/2 for a universe containing only dust.arrow_forwardWhy do Weinberg and other scientists seriously consider the possibility that the Standard Model is just a tentative explanation for the composition of the universe?arrow_forward
- The visible section of the Universe is a sphere centered on the bridge of your nose, with radius 13.7 billion light-years. (a) Explain why the visible Universe is getting larger, with its radius increasing by one light-year in every year. (b) Find the rate at which the volume of the visible section of the Universe is increasing.arrow_forwardThe temperature of the CMB today is T=2.725 K. Calculate the temperature of the CMB at redshift z=2000arrow_forwardConsider a universe where Big Bang nucleosynthesis produced significantly more 4He than 1H. Estimate the observed redshift, z, of the Cosmic Radiation Background (CMB) by an observer that observes the CMB to have a blackbody temperature of 2.715 K. Assume this universe has Ob = 0. 0486, QDM = O. 2588 and QA = 0. 6911arrow_forward
- Why do Weinberg and other scientists seriously consider the possibility that the Standard Model is just a tentative explanation for the composition of the universe? No handwrittenarrow_forwardIt can be shown that if an object orbiting a star of mass M in a circular orbit of radius R has speed v, then Rv? M Suppose a star orbits the center of the galaxy it is contained in with an orbit that is nearly circular with radius 18 R = 2.5 x 10 and velocity v = 230 km/s. Use the result above to estimate the mass of the portion of the galaxy inside the star's orbit (place all of this mass at the center of the orbit). Mass =arrow_forward(a) Calculate the approximate age of the universe from the average value of the Hubble constant, H0 = 20km/s ⋅ Mly . To do this, calculate the time it would take to travel 1 Mly at a constant expansion rate of 20 km/s. (b) If deceleration is taken into account, would the actual age of the universe be greater or less than that found here? Explain.arrow_forward
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