- Stars form in clusters, within clouds composed of gas mixed with dust.
- Three types of clusters can be seen in the Milky Way, with differing structures and evolutionary histories.
- The mass of the cloud that spawns a stellar group may account for these differences, by affecting the balance of contraction and expansion in the cluster.
- Only open clusters remain intact after the parent cloud has dispersed.
More In This Article
The night sky is a field of stars. In every direction, stars bright and dim fill the horizon to brimming. Some seem to form distinct patterns, which we recognize as constellations. Yet as beguiling as those patterns may be, most of them are no more than projections of the human mind. The vast majority of stars, in our own galaxy and in others, have no true physical connection to one another.
At least, not anymore. Every star actually begins its life in a group, surrounded by siblings of nearly the same age that only later drift apart. Astronomers know this because some of these stellar nurseries, called star clusters, still exist. The Orion nebula cluster is perhaps the most famous one: in images from the Hubble Space Telescope, its stars wink from within churning clouds of dust and gas. You can see the Pleiades cluster from your backyard: it is the fuzzy patch in the constellation Taurus.
This article was originally published with the title The Inner Life of Star Clusters.