Concept explainers
The size of the Milky Way is determined from studying stars in globular clusters.
Answer to Problem 1QP
Option (c) RR Lyrae is the correct option.
Explanation of Solution
A globular cluster is a spherical collection of stars that orbits a galactic core. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes, and relatively high stellar densities toward their centers.
RR Lyrae stars are easy to spot in globular clusters because they are relatively luminous and have a distinctive light curve. They lie in the instability strip of the Hertzsprung-Russell (H-R) diagram and suffer instabilities that cause their size to periodically change. This change in size also changes the temperature of the star giving rise to their variability.
The size of the Milky Way is determined from studying RR Lyrae stars in globular clusters.
Conclusion:
Since the period-luminosity relationship to determine the distances to globular clusters, option (c) is correct.
RR Lyrae is easy to spot in the globular cluster than the Cepheid variable. Thus, option (a) is incorrect.
Blue supergiant are found towards the top left of H-R diagram. Thus, option (b) is incorrect.
The density of stars inside a globular cluster is significantly higher than the density of stars around the Sun. Thus, option (d) is incorrect.
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Chapter 20 Solutions
21ST CENTURY ASTRONOMY (LL)W/SMARTWORK5
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