22: Stars from Adolescence to Old Age

Question 1

a loose group of young stars whose spectral types, motions, and positions in the sky indicate a common origin

Answer 1

association

Question 2

one of about 150 large, spherical star clusters (each with hundreds of thousands of stars) that form a spherical halo around the center of our Galaxy - among the oldest parts of our galaxy

Answer 2

globular cluster

Question 3

a nearly explosive ignition of helium in the triple-alpha process in the dense core of a red giant star

Answer 3

helium flash

Question 4

location in the H–R diagram where stars begin to leave the main sequence

Answer 4

main-sequence turnoff

Question 5

the building up of heavy elements from lighter ones by nuclear fusion

Answer 5

nucleosynthesis

Question 6

a comparatively loose cluster of stars, containing from a few dozen to a few thousand members, located in the spiral arms or disk of our Galaxy - sometimes referred to as a galactic cluster

Answer 6

open cluster

Question 7

a shell of gas ejected by and expanding away from an extremely hot low-mass star that is nearing the end of its life (they glow because of the ultra-violet energy of the central star)

Answer 7

planetary nebula

Question 8

a nuclear reaction by which three helium nuclei are built up (fused) into one carbon nucleus

Answer 8

triple-alpha process

Question 9

a line denoting the main sequence on the H–R diagram for a system of stars that
have completed their contraction from interstellar matter and are now deriving all their energy from nuclear reactions, but whose chemical composition has not yet been altered substantially by them - left-hand edge in H-R diagram

Answer 9

zero-age main sequence