Young Star Clusters

Young Stars Have Many Siblings

Typically, when star formation gets triggered in an interstellar cloud, hundreds to thousands of localized globules begin to collapse. The result is the birth of a cluster of stars. For example, the Trapezium stars in the Orion Nebula belong to a cluster of about 700 stars that were born about 1 million years ago. It is the youngest cluster of stars in the Orion cloud. Such clusters have been forming in this cloud for at least 12 million years, and the process continues today.


Stellar Siblings Are Not All the Same

The stars of a star cluster are not all the same. In our discussion above, we focused on the birth of a star like the Sun. Depending on the conditions in the interstellar cloud and the collapsing globules -- the mass of the cloud, the composition of the gas and dust, the amount of turbulence, and disturbances from nearby bright stars -- a wide variety of stars or star systems may form. Some stars are born single, like the Sun, surrounded by planets. Others are much smaller. A few are much bigger and more massive. And many are born as members of double, triple, or quadruple star systems.

Another example of a young star cluster in the Milky Way is the Pleiades in the constellation Taurus, the Bull. The cluster contains seven very massive and bright stars which, according to Greek mythology, were the daughters of Atlas. We call them the "Seven Sisters." The cluster's total number of stars is about 300. Most have masses like that of the Sun or less, and they are relatively faint. Some are single, while others belong to multiple star systems.