STELLAR POPULATIONS & KINEMATICS IN THE GALAXY General/Kinematics: ------------------ Constellations in astronomy are a) physical grouping of genuinely associated stars. $b) arbitrary but useful subdivisions of the sky. c) a conjuncture of planets. d) the most accurate way to predict the future. Which of the following statements are true? a) Stars aren't moving with respect to each other, although if they are nearby then they can appear to move due to parallax. b) Stars like the Sun emit only yellow light, while cooler stars emit only red light. c) Most of the twenty closest stars to the Sun are among the twenty brightest stars in the sky. d) All of the above are true. $e) None of the above are true. Suppose you measure the parallax of each star in the constellation Taurus (or any other constellation you might choose). Which of the following is the most likely? a) The stars all have the same parallax since we see them together in the same constellation b) The stars all have nearly the same parallax since they are moving together through space c) None of them has a measurable parallax since they are mostly within our own solar system $d) They may have significantly different parallaxes e) We cannot measure their parallaxes since they are all moving toward our Sun. Clusters: -------- If you find a cluster of very old stars, you would expect the cluster to appear a) very spread out $b) very concentrated toward its center c) shaped like a disk d) bipolar in shape, like a barbell As a star cluster evolves over time, a) the composition of the stars in the cluster changes from metal-poor to metal-rich $b) more and more main-sequence stars become red giants c) the cluster changes its location in the galaxy, getting closer to the spiral arms d) the shape of the cluster changes to a disk shape In a color-magnitude diagram of a star cluster, the blue end of the main sequence is useful for defining the age of the cluster because a) blue stars are not affected by extinction and reddening by dust. $b) stars just slightly brighter and redder are just now evolving off the main sequence to become giants. c) older, metal-poor stars are blue. b) the hottest stars are the oldest stars in a cluster. The difference in apparent magnitude of the main sequences of stars from two clusters in a color-magnitude diagram tells us a) how much each cluster has evolved b) if one cluster is "open" and the other is globular c) the relative ages of the clusters $d) the relative distances of the clusters Star clusters are useful to stellar astronomers because the clusters contain stars that a) are all about the same age. b) span a wide range of ages c) are all at the same stage of stellar evolution. $d) are all about the same age and distance. Because stars in clusters all have similar age and distance, the main underlying physical cause of their different appearances is their a) color b) radius $c) mass d) chemical composition e) temperature When making a color-magnitude diagram of a star cluster, we can use apparent brightness instead of intrinsic luminosity because $a) all stars in the cluster are at about the same distance b) all stars in the cluster have about the same age c) most stars in the cluster are on the main sequence d) reddening by interstellar dust does not affect clusters e) the cluster stars have similar chemical compositions Young stars contain metals while old stars do not because a) young stars are hotter than old stars b) young stars are more massive than old stars c) old stars have used up all their metals in producing energy $d) the gas out of which young stars were formed already contained metals produced by older stars