UNDERSTANDING THE UNIVERSE(LL)-W/CODE
3rd Edition
ISBN: 9780393869903
Author: PALEN
Publisher: NORTON
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Question
Chapter 15, Problem 41QAP
(a)
To determine
The distance of the Sun from the globular cluster.
(b)
To determine
The size of galaxy’s halo compared to the size of disk.
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Among the globular clusters orbiting a distant galaxy, one is moving at 534 km/s and is located 14 kpc from the center of the galaxy. Assuming the globular cluster is located outside most of the mass of the galaxy, what is the mass of the galaxy? Convert your answer to solar masses. (Hint: Use the formula for circular velocity,
Vc =
GM
r
;
make sure you convert relevant quantities to units of meters, kilograms, and seconds. Note: 1 pc = 3.1 ✕ 1016 m.)
Among the globular clusters orbiting a distant galaxy, one is moving at 417 km/s and is located 16 kpc from the center of the galaxy. Assuming the globular cluster is located outside most of the mass of the galaxy, what is the mass of the galaxy? Convert your answer to
solar masses. (Hint: Use the formula for circular velocity, V, = V
GM
; make sure you convert relevant quantities to units of meters, kilograms, and seconds. Note: 1 pc = 3.1 x 1016 m.)
solar masses (M.)
A given star orbits the center of its galaxy at an average speed of v_star, at a distance of r_star from the center. The galaxy has 2 spiral arms, and the arms themselves orbit slower than the star -- at the same radius, they orbit at a speed of v_arm (in the same direction as the star). The galaxy's age is t_gal. In the history of this galaxy, how many times did this star cross through a spiral arm?
Values: v_star = 200 km/s, r_star = 9 kpc, v_arms = 46 km/s, t_gal = 4 Gyr
Chapter 15 Solutions
UNDERSTANDING THE UNIVERSE(LL)-W/CODE
Ch. 15.1 - Prob. 15.1CYUCh. 15.2 - Prob. 15.2CYUCh. 15.3 - Prob. 15.3CYUCh. 15.4 - Prob. 15.4CYUCh. 15 - Prob. 1QAPCh. 15 - Prob. 2QAPCh. 15 - Prob. 3QAPCh. 15 - Prob. 4QAPCh. 15 - Prob. 5QAPCh. 15 - Prob. 6QAP
Ch. 15 - Prob. 7QAPCh. 15 - Prob. 8QAPCh. 15 - Prob. 9QAPCh. 15 - Prob. 10QAPCh. 15 - Prob. 11QAPCh. 15 - Prob. 12QAPCh. 15 - Prob. 13QAPCh. 15 - Prob. 14QAPCh. 15 - Prob. 15QAPCh. 15 - Prob. 16QAPCh. 15 - Prob. 17QAPCh. 15 - Prob. 18QAPCh. 15 - Prob. 19QAPCh. 15 - Prob. 20QAPCh. 15 - Prob. 21QAPCh. 15 - Prob. 22QAPCh. 15 - Prob. 23QAPCh. 15 - Prob. 24QAPCh. 15 - Prob. 25QAPCh. 15 - Prob. 26QAPCh. 15 - Prob. 27QAPCh. 15 - Prob. 28QAPCh. 15 - Prob. 29QAPCh. 15 - Prob. 30QAPCh. 15 - Prob. 31QAPCh. 15 - Prob. 32QAPCh. 15 - Prob. 33QAPCh. 15 - Prob. 34QAPCh. 15 - Prob. 35QAPCh. 15 - Prob. 36QAPCh. 15 - Prob. 37QAPCh. 15 - Prob. 38QAPCh. 15 - Prob. 39QAPCh. 15 - Prob. 40QAPCh. 15 - Prob. 41QAPCh. 15 - Prob. 42QAPCh. 15 - Prob. 43QAPCh. 15 - Prob. 44QAPCh. 15 - Prob. 45QAP
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- The 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_forwardThe 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_forwardWhy does star formation occur primarily in the disk of the Galaxy?arrow_forward
- Consider the following five kinds of objects: open cluster, giant molecular cloud, globular cluster, group of O and B stars, and planetary nebulae. A. Which occur only in spiral arms? B. Which occur only in the parts of the Galaxy other than the spiral arms? C. Which are thought to be very young? D. Which are thought to be very old? E. Which have the hottest stars?arrow_forwardDescribe what a typical star in the Galaxy would be like compared to the Sun.arrow_forwardThe globular clusters revolve around the Galaxy in highly elliptical orbits. Where would you expect the clusters to spend most of their time? (Think of Kepler’s laws.) At any given time, would you expect most globular clusters to be moving at high or low speeds with respect to the center of the Galaxy? Why?arrow_forward
- Look back at Figure 6.18 of Cygnus A and read its caption again. The material in the giant lobes at the edges of the image had to have been ejected from the center at least how many years ago? Figure 6.18 Radio Image. This image has been constructed of radio observations at the Very Large Array of a galaxy called Cygnus A. Colors have been added to help the eye sort out regions of different radio intensities. Red regions are the most intense, blue the least. The visible galaxy would be a small dot in the center of the image. The radio image reveals jets of expelled material (more than 160,000 light-years long) on either side of the galaxy. (credit: NRAO/AUI)arrow_forwardWhy does the disk of a spiral galaxy appear dark when viewed edge on?arrow_forwardIf 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_forward
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