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 47Q
To determine
The way by which the virtual particles explain dark energy and whether there are problems associated with this hypothesis.
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The matter density in the Universe today
is Pm = -27 kg m-3. What would
2.7 x 10
be the value of the density parameter,
2o, if the Hubble constant had the value
Ho = 38 km/s/Mpc? Assume the Universe
does not contain dark energy and choose
the option below that best matches your
answer.
Select one:
O a.
0.1
O b. 2.
О с.
1.
O d. 0.7
О е.
0.5
How does the Doppler effect on sound waves differ from the Doppler effect on electromagnetic
waves? Consider both cases: emitter moving and detector moving.
Spiral galaxies have been observed to have different Doppler shifts on each side. Why? Where do
the red and blue shifts come from?
Does Hubble's Law work well for galaxies in the Local Group (such as Andromeda)?
No, because dark energy is accelerating the universe's expansion over those distances.
No, because we do not know the precise value of Ho.
No, because Hubble did not know the Local Group existed when he discovered his law.
Yes, it works well for all galaxies.
No, because galaxies in the Local Group are bound gravitationally together.
Chapter 25 Solutions
Universe: Stars And Galaxies
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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
- Why cant an open universe have a center? How can a closed universe not have a center?arrow_forwardLarge redshifts move the positions of spectral lines to longer wavelengths and change what can be observed from the ground. For example, suppose a quasar has a redshift of =4.1 . At what wavelength would you make observations in order to detect its Lyman line of hydrogen, which has a laboratory or rest wavelength of 121.6 nm? Would this line be observable with a ground-based telescope in a quasar with zero redshift? Would it be observable from the ground in a quasar with a redshift of =4.1 ?arrow_forwardIn 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_forward
- It is possible to derive the age of the universe given the value of the Hubble constant and the distance to a galaxy, again with the assumption that the value of the Hubble constant has not changed since the Big Bang. Consider a galaxy at a distance of 400 million light-years receding from us at a velocity, v. If the Hubble constant is 20 km/s per million light-years, what is its velocity? How long ago was that galaxy right next door to our own Galaxy if it has always been receding at its present rate? Express your answer in years. Since the universe began when all galaxies were very close together, this number is a rough estimate for the age of the universe.arrow_forwardGiven that only about 5% of the galaxies visible in the Hubble Deep Field are bright enough for astronomers to study spectroscopically, they need to make the most of the other 95%. One technique is to use their colors and apparent brightnesses to try to roughly estimate their redshift. How do you think the inaccuracy of this redshift estimation technique (compared to actually measuring the redshift from a spectrum) might affect our ability to make maps of large-scale structures such as the filaments and voids shown in Figure 28.21? Figure 28.21 Sloan Digital Sky Survey Map of the Large-Scale Structure of the Universe. This image shows slices from the SDSS map. The point at the center corresponds to the Milky Way and might say “You Are Here!” Points on the map moving outward from the center are farther away. The distance to the galaxies is indicated by their redshifts (following Hubble’s law), shown on the horizontal line going right from the center. The redshift z=/ , where is the difference between the observed wavelength and the wavelength emitted by a nonmoving source in the laboratory. Hour angle on the sky is shown around the circumference of the circular graph. The colors of the galaxies indicate the ages of their stars, with the redder color showing galaxies that are made of older stars. The outer circle is at a distance of two billion light-years from us. Note that red (older stars) galaxies are more strongly clustered than blue galaxies (young stars). The unmapped areas are where our view of the universe is obstructed by dust in our own Galaxy. (credit: modification of work by M. Blanton and the Sloan Digital Sky Survey)arrow_forwardExplain what we mean when we call the universe homogeneous and isotropic. Would you say that the distribution of elephants on Earth is homogeneous and isotropic? Why?arrow_forward
- What does the term Hubble time mean in cosmology, and what is the current best calculation for the Hubble time?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_forwardIf a galaxy is 9.0 Mpc away from Earth and recedes at 488 km/s, what is H0 (in km/s/Mpc)? km/s/Mpc 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? 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. BIf the expansion of the Universe has been accelerating, the Universe could be substantially older than the value entered above.arrow_forward
- 1.2 1.0 0.8 0.6 Cosmic background data from COBE 0.4 0.2 0.0 0.5 10 Wavelength A in mm c) Background (CMB) undertaken by the COBE satellite. Use this diagram to estimate the current temperature of the CMB. Based on your estimate, what would the temperature of the CMB have been at a redshift of z = 5000? The left hand diagram above shows the results from observations of the Cosmic Microwave Radiated Intensity per Unit Wavelength (16° Watts/m per mm)arrow_forwardAre the galaxies red-shifting or blue-shifting? Explain. (You may find the big-bang theory helpful). Andromeda galaxy is currently approaching our galaxy with a radial velocity of 266 km/sec. How far is our galaxy from Andromeda? (Hubble’s constant, H, is 73 km/sec/MParsec). When can the two galaxies be anticipated to collide?arrow_forwardIf you find that the Hubble constant is double what we currently believe, how does this affect the calculated age of the universe? Group of answer choices It decreased it by a factor of four. It cuts it in half. It doubles it. It increases it by a factor of four.arrow_forward
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