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 22, Problem 29Q
To determine
To show:
That the form of the Kepler’s third law,
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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 19 kpc from the galaxy center and moving in a circular orbit with speed 369 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.]
(a) Estimate the height (z) above or below the Galactic plane for the globular cluster
M13 (1,b = 59°, 40.9°) and the Orion Nebula (1,b = 209°, -19.4°). M13 and the Orion
Nebula are 7 kpc and 450 pc away from Earth respectively.
(b) To which components of the Galaxy do these objects probably belong? Explain your
answers.
The difference in absolute magnitude between two objects at the same distance is related to their fluxes by the flux-magnitude relation.
FA
FB
= 2.51(MB − MA)
A distant galaxy contains a type I classical Cepheid whose period results in an absolute magnitude estimate of
−6.3.
If this star were placed next to our Sun
(M = +4.8)
and you observed them both from the same distance, how much more flux would the Cepheid emit than the Sun?
FCepheid
FSun
=
If a galaxy contains a supernova that at its brightest has an apparent magnitude of +11, how far away is the galaxy? Assume that the absolute magnitude of the supernova is
−18.
Hint:
Use the magnitude-distance formula:
d = 10(mV − MV + 5)/5 .
The hydrogen Balmer line H? has a wavelength of 486.1 nm. It is shifted to 559.7 nm in a quasar's spectrum. What is the redshift of this quasar? (Hint: What is Δ??)
Chapter 22 Solutions
Universe: Stars And Galaxies
Ch. 22 - Prob. 1QCh. 22 - Prob. 2QCh. 22 - Prob. 3QCh. 22 - Prob. 4QCh. 22 - Prob. 5QCh. 22 - Prob. 6QCh. 22 - Prob. 7QCh. 22 - Prob. 8QCh. 22 - Prob. 9QCh. 22 - Prob. 10Q
Ch. 22 - Prob. 11QCh. 22 - Prob. 12QCh. 22 - Prob. 13QCh. 22 - Prob. 14QCh. 22 - Prob. 15QCh. 22 - Prob. 16QCh. 22 - Prob. 17QCh. 22 - Prob. 18QCh. 22 - Prob. 19QCh. 22 - Prob. 20QCh. 22 - Prob. 21QCh. 22 - Prob. 22QCh. 22 - Prob. 23QCh. 22 - Prob. 24QCh. 22 - Prob. 25QCh. 22 - Prob. 26QCh. 22 - Prob. 27QCh. 22 - Prob. 28QCh. 22 - Prob. 29QCh. 22 - Prob. 30QCh. 22 - Prob. 31QCh. 22 - Prob. 32QCh. 22 - Prob. 33QCh. 22 - Prob. 34QCh. 22 - Prob. 35QCh. 22 - Prob. 36QCh. 22 - Prob. 37QCh. 22 - Prob. 38QCh. 22 - Prob. 39QCh. 22 - Prob. 40QCh. 22 - Prob. 41QCh. 22 - Prob. 42QCh. 22 - Prob. 43QCh. 22 - Prob. 44QCh. 22 - Prob. 45QCh. 22 - Prob. 46QCh. 22 - Prob. 47QCh. 22 - Prob. 48QCh. 22 - Prob. 49QCh. 22 - Prob. 50Q
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- Observations indicate that each galaxy contains a supermassive black hole at its center. These black holes can be hundreds of thousands to billions of times more massive than the Sun. Astronomers estimate the size of such black holes using multiple methods. One method, using the orbits of stars around the black hole, is an application of Kepler's third law. The mass of the black hole can be found by using the given equation, where a is the semi-major axis in astronomical units, P is the period in years, and k is a constant with a value of 1 Mo X year²/ AU³. a³ M = k- p² What is the mass of a supermassive black hole if a star orbits it with a semimajor axis of 959 AU and a period of 13.3 years? mass: Another method measures the speed of gas moving past the black hole. In the given equation, v is the velocity of the gas (in kilometers per second), r is the distance of the gas cloud from the black hole (in kilometers), and G is Newton's gravitational constant. In this equation, G = 1.33 ×…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_forwardThe best parallaxes obtained with Hipparcos have an accuracy of 0.001 arcsec. If you want to measure the distance to a star with an accuracy of 10%, its parallax must be 10 times larger than the typical error. How far away can you obtain a distance that is accurate to 10% with Hipparcos data? The disk of our Galaxy is 100,000 light-years in diameter. What fraction of the diameter of the Galaxy’s disk is the distance for which we can measure accurate parallaxes?arrow_forward
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