Copyright © 2010 Pearson Education, Inc. Clicker Questions Chapter 11 The Interstellar Medium

Copyright © 2010 Pearson Education, Inc. Question 1 Some regions of the Milky Way’s disk appear dark because 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.

Copyright © 2010 Pearson Education, Inc. Question 1 Some regions of the Milky Way’s disk appear dark because 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. Dust grains are about the same size as visible light, and they can scatter or block the shorter wavelengths.

Copyright © 2010 Pearson Education, Inc. 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.

Copyright © 2010 Pearson Education, Inc. 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.

Copyright © 2010 Pearson Education, Inc. Question 3 Astronomers use the term nebula to refer to a) outer envelopes of dying stars that drift gently into space. b) remnants of stars that die by supernova. c) clouds of gas and dust in interstellar space. d) distant galaxies seen beyond our Milky Way. e) All of the above are correct.

Copyright © 2010 Pearson Education, Inc. Question 3 Astronomers use the term nebula to refer to a) outer envelopes of dying stars that drift gently into space. b) remnants of stars that die by supernova. c) clouds of gas and dust in interstellar space. d) distant galaxies seen beyond our Milky Way. e) All of the above are correct. Nebula refers to any fuzzy patch – bright or dark – in the sky.

Copyright © 2010 Pearson Education, Inc. Question 4 Interstellar gas is composed primarily of a) 90% hydrogen, 9% helium, and 1% heavier elements. b) molecules including water and CO 2. c) 50% hydrogen, 50% helium. d) hydrogen, oxygen, and nitrogen. e) 99% hydrogen, and 1% heavier elements.

Copyright © 2010 Pearson Education, Inc. Question 4 Interstellar gas is composed primarily of a) 90% hydrogen, 9% helium, and 1% heavier elements. b) molecules including water and CO 2. c) 50% hydrogen, 50% helium. d) hydrogen, oxygen, and nitrogen. e) 99% hydrogen, and 1% heavier elements. The composition of interstellar gas mirrors that of the Sun, stars, and the jovian planets.

Copyright © 2010 Pearson Education, Inc. Question 5 a) gas and dust is moving away from Earth. b) hydrogen gas is present. c) dying stars have recently exploded. d) cool red stars are hidden inside. e) dust is present. The reddish color of emission nebulae indicates that

Copyright © 2010 Pearson Education, Inc. Question 5 a) gas and dust is moving away from Earth. b) hydrogen gas is present. c) dying stars have recently exploded. d) cool red stars are hidden inside. e) dust is present. The reddish color of emission nebulae indicates that Glowing hydrogen gas emits red light around the Horsehead nebula.

Copyright © 2010 Pearson Education, Inc. Question 6 21-centimeter radiation is important because 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.

Copyright © 2010 Pearson Education, Inc. Question 6 21-centimeter radiation is important because Cool atomic hydrogen gas produces 21-cm radio radiation as its electron “flips” its direction of spin. 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.

Copyright © 2010 Pearson Education, Inc. Question 7 Complex molecules in space are found a) in the photospheres of red giant stars. b) primarily inside dense dust clouds. c) in the coronas of stars like our Sun. d) scattered evenly throughout interstellar space. e) surrounding energetic young stars.

Copyright © 2010 Pearson Education, Inc. Question 7 Complex molecules in space are found a) in the photospheres of red giant stars. b) primarily inside dense dust clouds. c) in the coronas of stars like our Sun. d) scattered evenly throughout interstellar space. e) surrounding energetic young stars. A radio telescope image of the outer portion of the Milky Way, revealing molecular cloud complexes.

Copyright © 2010 Pearson Education, Inc. Question 8 Stars are often born within groups known as a) clans. b) spiral waves. c) aggregates. d) clusters. e) swarms.

Copyright © 2010 Pearson Education, Inc. Question 8 The Pleiades – a nearby open cluster – is a group of relatively young stars about 400 light-years from the Sun. Stars are often born within groups known as a) clans. b) spiral waves. c) aggregates. d) clusters. e) swarms.

Copyright © 2010 Pearson Education, Inc. Question 9 a) OB associations. b) molecular cloud complexes. c) aggregates. d) globular clusters. e) hives. Very young stars in small clusters of members are known as

Copyright © 2010 Pearson Education, Inc. Question 9 Very young stars in small clusters of members are known as NGC 3603 is a newborn cluster of hot young blue Type O and B stars – a perfect OB association. a) OB associations. b) molecular cloud complexes. c) aggregates. d) globular clusters. e) hives.

Copyright © 2010 Pearson Education, Inc. Question 10 All stars in a stellar cluster have roughly the same a) temperature. b) color. c) distance. d) mass. e) luminosity.

Copyright © 2010 Pearson Education, Inc. Question 10 All stars in a stellar cluster have roughly the same a) temperature. b) color. c) distance. d) mass. e) luminosity. Stars in the Pleiades cluster vary in temperature, color, mass, and luminosity, but all lie about 440 light-years away.

Copyright © 2010 Pearson Education, Inc. Question 11 Globular clusters are typically observed a) in the plane of our Galaxy. b) above or below the plane of our Galaxy. c) near to our Sun. d) in the hearts of other galaxies.

Copyright © 2010 Pearson Education, Inc. Question 11 Globular clusters are typically observed Globular clusters orbit the center of the Milky Way, and are usually seen above or below the galactic plane far from our Sun. a) in the plane of our Galaxy. b) above or below the plane of our Galaxy. c) near to our Sun. d) in the hearts of other galaxies.

Copyright © 2010 Pearson Education, Inc. Question 12 Stars in clusters & associations have about the same a) age. b) temperature. c) mass. d) color. e) luminosity.

Copyright © 2010 Pearson Education, Inc. Question 12 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. a) age. b) temperature. c) mass. d) color. e) luminosity.

Copyright © 2010 Pearson Education, Inc. 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.

Copyright © 2010 Pearson Education, Inc. 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

Copyright © 2010 Pearson Education, Inc. Question 14 How do single stars form within huge clouds of interstellar gas and dust? a) Clouds fragment into smaller objects, forming many stars at one time. b) One star forms; other matter goes into planets, moons, asteroids, & comets. c) Clouds rotate & throw off mass until only enough is left to form one star.

Copyright © 2010 Pearson Education, Inc. Question 14 How do single stars form within huge clouds of interstellar gas and dust? a) Clouds fragment into smaller objects, forming many stars at one time. b) One star forms; other matter goes into planets, moons, asteroids, & comets. c) Clouds rotate & throw off mass until only enough is left to form one star. The theory of star formation predicts stars in a cluster would form about the same time.

Copyright © 2010 Pearson Education, Inc. Question 15 What is a T- Tauri star? a) a collapsing cloud of gas about to become a protostar b) a dying star c) a cool main sequence star d) a star releasing a planetary nebula e) a protostar about to become a star

Copyright © 2010 Pearson Education, Inc. Question 15 What is a T- Tauri star? a) a collapsing cloud of gas about to become a protostar b) a dying star c) a cool main sequence star d) a star releasing a planetary nebula e) a protostar about to become a star T-Tauri stars often show jets of gas emitted in two directions — “bipolar flow” — suggesting they are not yet stable.

Copyright © 2010 Pearson Education, Inc. Question 16 A key feature of globular clusters is that they have a ) very few cool stars. b) the oldest stars in our Galaxy. c) lots of massive main sequence stars. d) stars with very different ages. e) high concentrations of metals.

Copyright © 2010 Pearson Education, Inc. Question 16 A key feature of globular clusters is that they have a ) very few cool stars. b) the oldest stars in our Galaxy. c) lots of massive main sequence stars. d) stars with very different ages. e) high concentrations of metals. The H–R diagram of a globular cluster has a low “turnoff point” indicating its extreme age.