1. Review Quiz No. 17 :60 1.The radius in the interior of a star where fusion processes can no longer take place. 2.The point in time of a star’s life when nuclear fusion of hydrogen into helium ceases. 3.The point in time of a star’s life when nuclear fusion processes cease alltogether. 4.The point in a rotating star cluster beyond which a star is no longer gravitationally bound to the cluster. 5.The point on the main sequence of a star cluster above which stars have evolved to red giants. Question 1: What is the “Turn- Off Point”?

2. Question 2: Comparing the Hertzsprung-Russell diagrams of 2 star clusters, A and B, you find that the turn-off point of cluster A occurs in the range of F stars, while that of cluster B occurs in the range of K stars. From this, you can infer that … :45 1.A is closer to us than B. 2.B is closer to us than A. 3.A is older than B. 4.B is older than A. 5.A contains more stars than B.

3. Question 3: The longer a Cepheid variable’s oscillation period, … :45 1.the brighter (more luminous) it is. 2.the fainter (more luminous) it is. 3.the longer its rotation period is. 4.the shorter its rotation period is. 5.the younger it is.

4. Question 4: Cepheid variables can be used for distance measurements … :45 1.only within the solar system. 2.only in the immediate solar neighborhood 3.only within our Milky Way. 4.to neighboring galaxies. 5.throughout the entire visible Universe.