question: What are groups of stars called that are smaller than a galaxy?
distractor3: constellations
distractor1: Milky Way
distractor2: nebuli
correct_answer: star clusters
support: Star clusters are groups of stars smaller than a galaxy. There are two main types, open clusters and globular clusters. Open clusters are groups of up to a few thousand stars held together by gravity. The Jewel Box, shown in Figure below , is an open cluster. Open clusters tend to be blue in color, and often contain glowing gas and dust. The stars in an open cluster are young stars that all formed from the same nebula.