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This lecture discusses the effects of interstellar dust on the observation of stars, explaining why certain regions of the Milky Way appear dark. It covers how light from stars is dimmed and reddened when passing through interstellar dust and gas, leading to observable phenomena like beautiful sunsets. The composition of interstellar gas is outlined, highlighting the importance of 21-centimeter radiation in revealing stellar structures. Additionally, the lecture delves into the characteristics of stars in clusters and the formation rates of massive stars, particularly in contexts like Omega Centauri.
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LECTURE 17, OCTOBER 28, 2010 ASTR 101, SECTION 3 INSTRUCTOR, JACK BRANDT jcbrandt@unm.edu ASTR 101-3, FALL 2010
Question 1 a) there are no stars there. b) stars in that direction are obscured by interstellar gas. c) stars in that direction are obscured by interstellar dust. d) numerous black holes capture all the starlight behind them. Some regions of the Milky Way’s disk appear dark because
Question 1 a) there are no stars there. b) stars in that direction are obscured by interstellar gas. c) stars in that direction are obscured by interstellar dust. d) numerous black holes capture all the starlight behind them. Some regions of the Milky Way’s disk appear dark because Dust grains are about the same size as visible light, and they can scatter or block the shorter wavelengths.
Question 2 When a star’s visible light passes through interstellar dust, the light we see a) is dimmed and reddened. b) appears to twinkle. c) is Doppler shifted. d) turns bluish in color. e) ionizes the dust and creates emission lines.
Question 2 When a star’s visible light passes through interstellar dust, the light we see a) is dimmed and reddened. b) appears to twinkle. c) is Doppler shifted. d) turns bluish in color. e) ionizes the dust and creates emission lines. The same process results in wonderful sunsets, as dust in the air scatters the Sun’s blue light, leaving dimmer, redder light.
Question 4 a) 90% hydrogen, 9% helium, and 1% heavier elements. b) molecules including water and CO2. c) 50% hydrogen, 50% helium. d) hydrogen, oxygen, and nitrogen. e) 99% hydrogen, and 1% heavier elements. Interstellar gas is composed primarily of
Question 4 a) 90% hydrogen, 9% helium, and 1% heavier elements. b) molecules including water and CO2. c) 50% hydrogen, 50% helium. d) hydrogen, oxygen, and nitrogen. e) 99% hydrogen, and 1% heavier elements. Interstellar gas is composed primarily of The composition of interstellar gas mirrors that of the Sun, stars, and the jovian planets.
Question 6 a) its radio waves pass unaffected through clouds of interstellar dust. b) it arises from cool helium gas present throughout space. c) it can be detected with optical telescopes. d) it is produced by protostars. e) it reveals the structure of new stars. 21-centimeter radiation is important because
Question 6 a) its radio waves pass unaffected through clouds of interstellar dust. b) it arises from cool helium gas present throughout space. c) it can be detected with optical telescopes. d) it is produced by protostars. e) it reveals the structure of new stars. 21-centimeter radiation is important because Cool atomic hydrogen gas produces 21-cm radio radiation as its electron “flips” its direction of spin.
Question 12 a) age. b) temperature. c) mass. d) color. e) luminosity. Stars in clusters & associations have about the same
Question 12 a) age. b) temperature. c) mass. d) color. e) luminosity. Stars in clusters & associations have about the same Most of the stars in a cluster form about the same time. Stars in the Omega Centauri globular cluster are estimated to be about 14 billion years old.
Question 13 Objects more massive than our Sun form into stars a) much slower, over billions of years. b) in about the same time. c) much faster, over tens of thousands of years. d) not at all – they are unstable.
Question 13 Objects more massive than our Sun form into stars a) much slower, over billions of years. b) in about the same time. c) much faster, over tens of thousands of years. d) not at all – they are unstable. More mass faster collapse More mass faster start of fusion reactions More mass a hotter, more luminous main sequence star
