Astronomy
1st Edition
ISBN: 9781938168284
Author: Andrew Fraknoi; David Morrison; Sidney C. Wolff
Publisher: OpenStax
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Textbook Question
Chapter 26, Problem 27E
According to Hubble’s law, what is the recessional velocity of a galaxy that is 108 light-years away from us? (Assume a Hubble constant of 22 km/s per million light-years.)
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If a galaxy is 18 Mpc from Earth and the Hubble constant is 70 km/s/Mpc, what is the recession velocity of the galaxy (in km/s)?
A galaxy is receding from Earth at a speed of 300 km/s and the Hubble constant is 70 km/s/Mpc. What is the distance to the galaxy (in Mpc)?
If the active core of a galaxy contains a black hole of 106 M,
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Hint: Use the formula for circular velocity, V.
GM
V
hr
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Chapter 26 Solutions
Astronomy
Ch. 26 - Describe the main distinguishing features of...Ch. 26 - Why did it take so long for the existence of other...Ch. 26 - Explain what the mass-to-light ratio is and why it...Ch. 26 - If we now realize dwarf ellipticals are the most...Ch. 26 - What are the two best ways to measure the distance...Ch. 26 - What are the two best ways to measure the distance...Ch. 26 - Why is Hubble’s law considered one of the most...Ch. 26 - What does it mean to say that the universe is...Ch. 26 - Was Hubble’s original estimate of the distance to...Ch. 26 - Does an elliptical galaxy rotate like a spiral...
Ch. 26 - Why does the disk of a spiral galaxy appear dark...Ch. 26 - What causes the largest mass-to-light ratio: gas...Ch. 26 - What is the most useful standard bulb method for...Ch. 26 - When comparing two isolated spiral galaxies that...Ch. 26 - If all distant galaxies are expanding away from...Ch. 26 - Is the Hubble constant actually constant?Ch. 26 - Where might the gas and dust (if any) in an...Ch. 26 - Why can we not determine distances to galaxies by...Ch. 26 - Which is redder-a spiral galaxy or an elliptical...Ch. 26 - Suppose the stars in an elliptical galaxy all...Ch. 26 - Starting with the determination of the size of...Ch. 26 - Suppose the Milky Way Galaxy were truly isolated...Ch. 26 - Suppose you were Hubble and Humason, working on...Ch. 26 - What does it mean if one elliptical galaxy has...Ch. 26 - Based on your analysis of galaxies in Table 26.1,...Ch. 26 - Can a higher mass-to-light ratio mean that there...Ch. 26 - According to Hubble’s law, what is the recessional...Ch. 26 - A cluster of galaxies is observed to have a...Ch. 26 - Suppose we could measure the distance to a galaxy...Ch. 26 - Calculate the mass-to-light ratio for a globular...Ch. 26 - Calculate the mass-to-light ratio for a luminous...
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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
- If the diameter of the Milky Way Galaxys visible disk, 80,000 ly, is represented in a model by a dinner plate with a diameter of 10 inches, what is the model distance to galaxy M31, 2.6 millionly away? What is the model distance to the Virgo galaxy cluster, 16 Mpc away? (Convert answers to feet.)arrow_forwardIf we now realize dwarf ellipticals are the most common type of galaxy, why did they escape our notice for so long?arrow_forwardCould the Milky Way ever become an active galaxy? Is it likely to ever be as luminous as a quasar?arrow_forward
- Suppose we could measure the distance to a galaxy using one of the distance techniques listed in Table 26.2 and it turns out to be 200 million light-years. The galaxy’s redshift tells us its recessional velocity is 5000 km/s. What is the Hubble constant?arrow_forwardWhat evidence can you give that we live in a galaxy?arrow_forwardWe have said that the Galaxy rotates differentially; that is, stars in the inner parts complete a full 360° orbit around the center of the Galaxy more rapidly than stars farther out. Use Kepler’s third law and the mass we derived in Exercise 25.19 to calculate the period of a star that is only 5000 light-years from the center. Now do the same calculation for a globular cluster at a distance of 50,000 light-years. Suppose the Sun, this star, and the globular cluster all fall on a straight line through the center of the Galaxy. Where will they be relative to each other after the Sun completes one full journey around the center of the Galaxy? (Assume that all the mass in the Galaxy is concentrated at its center.)arrow_forward
- Assume that the average galaxy contains 1011MSunand that the average distance between galaxies is 10 million light-years. Calculate the average density of matter (mass per unit volume) in galaxies. What fraction is this of the critical density we calculated in the chapter?arrow_forwardGiven the ideas presented here about how galaxies form, would you expect to find a giant elliptical galaxy in the Local Group? Why or why not? Is there in fact a giant elliptical in the Local Group?arrow_forwardSuppose the stars in an elliptical galaxy all formed within a few million years shortly after the universe began. Suppose these stars have a range of masses, just as the stars in our own galaxy do. How would the color of the elliptical change over the next several billion years? How would its luminosity change? Why?arrow_forward
- When comparing two isolated spiral galaxies that have the same apparent brightness, but rotate at different rates, what can you say about their relative luminosity?arrow_forwardWhy didnt astronomers before Shapley realize how large our Galaxy is?arrow_forwardUsing the information from Example 28.1, how much fainter an object will you have to be able to measure in order to include the same kinds of galaxies in your second survey? Remember that the brightness of an object varies as the inverse square of the distance.arrow_forward
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