The Milky Way - Quiz 15

1. One way astronomers deduce that the Milky Way has a disk is that they
A).. see stars arranged in a circular region around the north celestial pole.
B)..see far more stars along the band of the Milky Way than in other directions.
C).. see a large dark circle silhouetted against the Milky Way in the Southern hemisphere.
D).. see the same number of stars in all directions in the sky.
E).. None of the above.

2. Astronomers think the Milky Way has spiral arms because
A)...they can see them unwinding along the celestial equator.
B)... radio maps show that gas clouds are distributed in the disk with a spiral pattern.
C)...young star clusters, HII regions, and associations outline spiral arms.
D)...globular clusters outline spiral arms.
E)...Both (B) and (C) are correct.

3. A young blue star moving along a circular orbit in the disk is a
A)... Pop I star.
B)... Pop II star.
C)... Pop X star.

4. The modified form of Kepler's third law allows astronomers to determine the Milky Way's
A)... mass.
B)... age.
C)... composition.
D)... shape.
E)... number of spiral arms.

5. Astronomers know that interstellar matter exists because
A)... they can see it in dark clouds and clouds that absorb light.
B)... the matter creates narrow absorption lines in the spectra of some stars.
C)... they can detect radio waves coming from atoms and molecules in the cold gas.
D)... spacecraft have sampled clouds near Orion.
E)... All the above except (D).

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