Protobinary Star

Definition

Binaries are pairs of stars locked into orbit around each other by their mutual gravitational attraction. When both stars are too young to undergo hydrogen fusion, the system is called a protobinary. In the very youngest protobinaries, neither star is optically visible, since both are still heavily embedded in the dust and gas that formed them. Several hundred protobinaries are known. In a few cases, the actual orbits of the component stars have been partially traced. Most protobinaries, however, are detected as close pairs of stars that share a common space motion within a young stellar cluster.

Overview

Most stars are not isolated objects, but have an orbiting companion. This fundamental fact was first established in the 1960s through surveys of main-sequence G-type stars, i.e., objects similar to the Sun. Over the last two decades, it has emerged that pairing is also common among much younger stars. The term protobinary refers to a pair of stars in which the components...