Astronomy
1st Edition
ISBN: 9781938168284
Author: Andrew Fraknoi; David Morrison; Sidney C. Wolff
Publisher: OpenStax
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Textbook Question
Chapter 25, Problem 19E
The Sun orbits the center of the Galaxy in 225 million years at a distance of 26,000 light-years. Given that
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Students have asked these similar questions
A star at a distance of 50000 light years from the center of a galaxy has an orbital speed of 100 km/s around the galactic center. What is the total mass of the galaxy located at distances smaller than 50000 light years from the center?
A. 7.6 ×1010 solar masses
B. 4.2 ×1011 solar masses
C. 3.5 ×1010 solar masses
D. 1.4 ×1011 solar masses
Is the answer C?
M = (r x v^2) / G
= 50000 x 9.46e15 x (100000^2) / 6.67e-11 / 2e30 (the Sun's mass)
= 3.55e10 solar masses
A star near the visible edge of a galaxy travels in a uniform circular orbit. It is 43,500 ly (light-years) from the galactic center and has a speed of 275 km/s.
a.)Estimate the total mass of the galaxy based on the motion of the star. Gravitational constant is 6.674×10−11m3/(kg·s2) and mass of the Sun Ms=1.99 × 1030 kg.
b.)The total visible mass (i.e., matter we can detect via electromagnetic radiation) of the galaxy is 1011 solar masses. What fraction of the total mass of the galaxy is visible, according to this estimate?
Suppose that the outer stars of a galaxy have an orbital velocity of 150 km/s. If the radius of the galaxy is 4.0 kpc (1??? = 3.1 × 1016 ??), what is the orbital period of the outer
stars in years?
Chapter 25 Solutions
Astronomy
Ch. 25 - Explain why we see the Milky Way as a faint band...Ch. 25 - Explain where in a spiral galaxy you would expect...Ch. 25 - Describe several characteristics that distinguish...Ch. 25 - Briefly describe the main parts of our Galaxy.Ch. 25 - Describe the evidence indicating that a black hole...Ch. 25 - Explain why the abundances of heavy elements in...Ch. 25 - What will be the long-term future of our Galaxy?Ch. 25 - Suppose the Milky Way was a band of light...Ch. 25 - Suppose somebody proposed that rather than...Ch. 25 - The globular clusters revolve around the Galaxy in...
Ch. 25 - Shapley used the positions of globular clusters to...Ch. 25 - Consider the following five kinds of objects: open...Ch. 25 - The dwarf galaxy in Sagittarius is the one closest...Ch. 25 - Suppose three stars lie in the disk of the Galaxy...Ch. 25 - Why does star formation occur primarily in the...Ch. 25 - Where in the Galaxy would you expect to find Type...Ch. 25 - Suppose that stars evolved without losing...Ch. 25 - Assume that the Sun orbits the center of the...Ch. 25 - The Sun orbits the center of the Galaxy in 225...Ch. 25 - Suppose the Sun orbited a little farther out, but...Ch. 25 - We have said that the Galaxy rotates...Ch. 25 - If our solar system is 4.6 billion years old, how...Ch. 25 - Suppose the average mass of a star in the Galaxy...Ch. 25 - The first clue that the Galaxy contains a lot of...Ch. 25 - The best evidence for a black hole at the center...Ch. 25 - The next step in deciding whether the object in...Ch. 25 - Suppose the Sagittarius dwarf galaxy merges...
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- The center of a faint but active galaxy has magnitude 26. How much less bright does it look than the very faintest star that our eyes can see, roughly magnitude 6?arrow_forwardSuppose three stars lie in the disk of the Galaxy at distances of 20,000 light-years, 25,000 light-years, and 30,000 light-years from the galactic center, and suppose that right now all three are lined up in such a way that it is possible to draw a straight line through them and on to the center of the Galaxy. How will the relative positions of these three stars change with time? Assume that their orbits are all circular and lie in the plane of the disk.arrow_forwardwhat is the difference between an E0 galaxy and an E1 galaxy?arrow_forward
- You observe a star orbiting in the outer parts of a galaxy. The distance to this galaxy is known, and you are able to take a spectra of this star and determine its velocity. The star is 22 kpc from the galaxy center and moving in a circular orbit with speed 304 km/s. Compute the total mass of the galaxy internal to the star's orbit. You will get a large number; express it in scientific notation and in units of solar masses [e.g., 4.2e10]. [Hint: there is a Box in Chapter 22 of your textbook that will be of help. See also the course formula sheet.]arrow_forwardWhat color is the center of this galaxy and why?arrow_forwardThe Sun has an orbital speed of about 220 kms−1 around the centre of the Galaxy, whose distance is 28 000 light years. Estimate the total mass of the Galaxy in solar masses.arrow_forward
- Suppose you have obtained spectra of several galaxies and have measured the observed wavelength of the H-Alpha line (rest wavelength = 656.3 nm) to be Galaxy 1: 658.1 nm. Galaxy 2: 667.1 nm. Galaxy 3: 677.6 nm. Calculate the radial velocity of each of these galaxies.arrow_forwardthe sun has an orbital speed of about 220kms^-1 around the centre of the galaxy , whose distance is 28 000 light years.estimate the total mass of the galaxy in solar massesarrow_forwardAn astronomer observed the motions of some galaxies. Based on his observations, he made the following statements. Which one of them is most likely to be false? Take Hubble's constant to be 67 km/s/Mpc. A. A galaxy observed to be moving away from us at a speed of 70 km/s is at a distance of about 1 Mpc from us. B. A galaxy observed to be moving away from us at a speed of 700 km/s is at a distance of about 10 Mpc from us. C. A galaxy observed to be moving away from us at a speed of 7000 km/s is at a distance of about 100 Mpc from us. D. A galaxy observed to be moving away from us at a speed of 70000 km/s is at a distance of about 1 Gpc from us. Is the answer D? Thank you!arrow_forward
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