1. LECTURE 21, NOVEMBER 16, 2010 ASTR 101, SECTION 3 INSTRUCTOR, JACK BRANDT jcbrandt@unm.edu 1ASTR 101-3, FALL 2010

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10. a) measuring distances with Cepheid variable stars. b) identifying the mass of the Galaxys central black hole. c) determining the masses of stars in an eclipsing binary system. d) using spectroscopic parallax to measure distances to stars. Question 3 The period – luminosity relationship is a crucial component of

11. a) measuring distances with Cepheid variable stars. b) identifying the mass of the Galaxys central black hole. c) determining the masses of stars in an eclipsing binary system. d) using spectroscopic parallax to measure distances to stars. Question 3 The period – luminosity relationship is a crucial component of Cepheid variable stars with longer periods have higher actual luminosities; short-period Cepheids are dimmer.

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15. a) supernova remnants. b) white dwarf stars in the spiral arms. c) red giant variable stars in globular clusters. d) bright O and B stars in open clusters. e) X-ray sources. Question 1 The location of the galactic center was identified using

16. a) supernova remnants. b) white dwarf stars in the spiral arms. c) red giant variable stars in globular clusters. d) bright O and B stars in open clusters. e) X-ray sources. Question 1 The location of the galactic center was identified using Harlow Shapley used pulsating RR-Lyrae variables as distance indicators to the globular clusters. He then deduced the distance and direction of the Milky Ways center.

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22. a) the spiral arms formed first. b) the globular clusters formed first. c) the disk component started out thin and grew. d) spiral density waves formed first. e) the bar in the bulge formed first. Question 7 In the formation of our Galaxy

23. a) the spiral arms formed first. b) the globular clusters formed first. c) the disk component started out thin and grew. d) spiral density waves formed first. e) the bar in the bulge formed first. Question 7 In the formation of our Galaxy Globular clusters contain very old stars, no gas or dust, and orbit around the center randomly.

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26. a) a spiral galaxy. b) a barred spiral galaxy. c) an elliptical galaxy. d) a quasar. e) an irregular galaxy. Question 5 Detailed measurements of the disk suggest that our Milky Way is

27. a) a spiral galaxy. b) a barred spiral galaxy. c) an elliptical galaxy. d) a quasar. e) an irregular galaxy. Question 5 Detailed measurements of the disk suggest that our Milky Way is Measurements of stellar motion in and near the bulge imply that it is football shaped, about half as wide as it is long, characteristic of a barred spiral galaxy.

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34. a) the Suns mass and velocity in orbit around the galactic center b) the rotation of the bulge and disk components c) the Suns age and age of globular cluster stars d) the motion of spiral arms and the mass of the central black hole e) the Suns orbital period and distance from the center Question 6 What two observations allow us to estimate the Galaxys mass?

35. Question 6 What two observations allow us to estimate the Galaxys mass? Use the modified form of Keplers law to find the mass: Total mass = (orbital size) 3 / (orbital period) 2 a) the Suns mass and velocity in orbit around the galactic center b) the rotation of the bulge and disk components c) the Suns age and age of the globular cluster stars d) the motion of spiral arms and mass of the central black hole e) the Suns orbital period and distance from the center

36. Question 10 a) 21-cm maps of the spiral arms b) the rotation curve of the outer edges of the Galaxy c) orbits of open clusters in the disk d) infrared observations of new star- forming regions e) X-ray images of other galaxies What suggests that the mass of our Galaxy extends farther than its visible disk?

37. a) 21-cm maps of the spiral arms b) the rotation curve of the outer edges of the Galaxy c) orbits of open clusters in the disk d) infrared observations of new star- forming regions e) X-ray images of other galaxies Question 10 What suggests that the mass of our Galaxy extends farther than its visible disk? The outer edges of the Galaxys disk rotate much faster than they should. Most of the mass of the Galaxy must be dark matter.

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42. a) tidal forces from the Andromeda Galaxy. b) accretion disks around neutron stars. c) gamma-ray bursts. d) gravitation from globular clusters. e) a supermassive black hole. Question 4 High-speed motion of gas and stars near the Milky Way Galaxys center is explained by

43. Question 4 High-speed motion of gas and stars near the Milky Way Galaxys center is explained by Recent observations estimate the black hole to be 4 million solar masses. a) tidal forces from the Andromeda Galaxy. b) accretion disks around neutron stars. c) gamma-ray bursts. d) gravitation from globular clusters. e) a supermassive black hole.

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