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The stars formed from the same giant molecular cloud and are roughly the same age.
It can be called a star cluster, an open cluster or an asterism.
similar age and composition.
Open Cluster
open cluster
Because of the high percentage of OB stars, the cluster is a relatively young cluster. M26 has an estimated age of only about 25 million years.
The density of the stars.
The stars formed from the same giant molecular cloud and are roughly the same age.
The smallest galaxy - a dwarf galaxy - will contain stars upwards of 30 billion stars. You are thinking of an open cluster, which as the name suggests, is a cluster of stars, not a galaxy. An open cluster is a group of up to a few thousand stars.
It can be called a star cluster, an open cluster or an asterism.
Open Cluster
Constellation or "asterism". The difference is that "constellations" are officially recognized by the International Astronomical Union, while an "asterism" is any other pattern or grouping of stars.
Whooooo there. That is a silly question. You or you teacher is forgetting about the total number of stars within a galaxy and cluster. Whilst a globular cluster has mainly older stars compared to an open cluster it will only contain a few billion stars, whereas a galaxy can have upwards of 500 billion stars, many of them old. So the answer is not definitive, but I think the answer you are looking for is global clusters.
An open cluster.
similar age and composition.
Some of the brightest stars in the open cluster are found in the "Plough" or the "Ursa Major" just like the Epilson Ursai Majoris.
Open cluster