Concept explainers
(a)
The recessional velocity, if it is given that the galaxy RD1 has a redshift value of
(a)
Answer to Problem 30Q
Solution:
Explanation of Solution
Given data:
The value of the redshift (z) is
Formula used:
The expression for the the recessional velocity is written as,
Here,
Explanation:
Recall the expression for the recessional velocity.
Substitute
Further, solve the above expression for
Substitute
Conclusion:
Thus, the recessional velocity of the galaxy is
(b)
The recessional velocity, if it is given that galaxy RD1 has a redshift value of
(b)
Answer to Problem 30Q
Solution:
Explanation of Solution
Given data:
The value of redshift (z) is
Formula used:
The expression for low speed formula is written as,
Here,
Explanation:
Recall the expression for low speed formula.
Substitute
Solve the above expression for
The recessional velocity from low-speed formula comes out to be
Conclusion:
Thus, the recessional velocity as calculated from a low-speed formula comes out to be very large, which is not possible.
(c)
The distance to galaxy RD1 from Earth in MPc, as well as in light-years, with the help of Hubble’s law, if the Hubble constant is
(c)
Answer to Problem 30Q
Solution:
Explanation of Solution
Given data:
The value of the Hubble’s constant is
Formula used:
According to Hubble's law,
Here,
Explanation:
Recall the expression for Hubble’s law and rearrange it for
Substitute
The conversion factor of megaparsecs into light year is
Thus,
Conclusion:
The distance to galaxy RD1 is
Want to see more full solutions like this?
Chapter 23 Solutions
Universe
- Suppose you were Hubble and Humason, working on the distances and Doppler shifts of the galaxies. What sorts of things would you have to do to convince yourself (and others) that the relationship you were seeing between the two quantities was a real feature of the behavior of the universe? (For example, would data from two galaxies be enough to demonstrate Hubble’s law? Would data from just the nearest galaxies-in what astronomers call “the Local Group”-suffice?)arrow_forwardExplain how the Hubble constant, H0, can be used to make an estimate for the age of the Universe. Use the value of H0 = 0.07×103 kms-1/Mpc to estimate the Universe’s age. Comment on the significance of your answer.arrow_forwardIt 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 235 million light-years receding from us at a velocity, v. If the Hubble constant is 20.5 km/s per million light-years, what is its velocity? (Enter the magnitude in km/s.) _________ km/sarrow_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_forwardFigure 2 shows the "rotation curve" of NGC 2742. It plots the “radial velocity (V)" (how fast material is moving either toward or away from us) that is measured for objects at different distances (R = radius") from the center of the galaxy. The center of the galaxy is at 0 kpc (kiloparsecs) with a speed of 9 km/sec away from us. (These velocities have been corrected for the observed tilt of the galaxy and represent true orbital velocities of the stars and gas.) 200 100 U4779 -100 As you can see, one side of the galaxy is moving with a negative velocity (spinning toward us), while the other side has a positive velocity (spinning away from us). Using Newton's gravity equation, we will be able to determine the gravitational mass of the entire galaxy and how the mass varies versus distance from the galaxy's center. -200 -8 8 -4 Radius (kpc) Read the following text carefully and follow the instructions: Select five radii spaced evenly from 0-10 kpc across the galaxy. Your selections should…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
- Suppose a universe is spatially flat, and (at some moment in time) has density ρ. Suppose a creature living in one galaxy in this universe sees a second galaxy receding (at this same moment in time), with its spectral lines redshifted by a factor of z. How far away is the second galaxy from the first? (Note the distance is small enough that Hubble's law can be safely applied.) Values: ρ = 5x10-27 kg m-3 z = 0.10 Enter your answer in Mpc, rounded to the nearest integer.arrow_forwardIf a galaxy is 9.0 Mpc away from Earth and recedes at 510 km/s, what is H? What is the Hubble time?arrow_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 galaxy with a spherically symmetric distribution of matter has a mass density profile of the type p(r) ∞ 1/r, where r is the radial coordinate from the centre of the galaxy. To what type of circular velocity (r) does this correspond? Select one: a. (r) O b. c. O d. (r) ~ r (r) ~ √r (r): = constantarrow_forwardPretend that galaxies are spaced evenly, 7.0 Mpc apart, and the average mass of a galaxy is 1.0 ✕ 1011 M. What is the average density (in kg/m3) of matter in the universe? (Note: The volume of a sphere is 4/3pieR^3 and the mass of the sun is 2.0 ✕ 1030 kg.) ______ kg/m^3 Which model universe does this density value support? A: open B: flat C: closedarrow_forwardThe 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 = )arrow_forward
- AstronomyPhysicsISBN:9781938168284Author:Andrew Fraknoi; David Morrison; Sidney C. WolffPublisher:OpenStaxPrinciples of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningStars and Galaxies (MindTap Course List)PhysicsISBN:9781337399944Author:Michael A. SeedsPublisher:Cengage Learning