Astronomy Unit 5

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 system of clusters in the center of our Galaxy

Answer 2

global 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 (the nebulae 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