Answer Happy

QUESTION 20 In binary stars, the two stars move in which way with respect to each other? O a. The low-mass star moves in a circular orbit around the stationary high-mass star Ob in straight lines, back and forth past each other. O c. In circular orbits around the center of the galaxy d. In elliptical orbits, about a common "center of mass QUESTION 21 On the HR diagram, the Sun lies a. At the top left O b. At the bottom left c. At the bottom right d. About the middle of the main sequence

QUESTION 22 Nuclear reactions in the interior of star murovide energy at a rate that equals the star's O a output of radiation b. surface temperature e chemical composition d. ago QUESTION 23 when the core of a star shrinks after hydrogen fusion stops, O a. the core cools and the star expands, O b. the core cools and the star contracts c. the core heats and the star expands. d. the core heats and the star contracts. QUESTION 24 As a one solar mass star evolves to the red giant stage: O a. its surface temperature and its luminosity increase. b. Its surface temperature and its luminosity decrease. c. its luminosity decreases and its surface temperature increases. d. Its luminosity increases and its surface temperature decreases.