Double stars are pairs of stars that are close to each other in the sky. They can be seen as a single point of light through a telescope, but they are actually two distinct stars that may be orbiting around a common center of mass. Some double stars are physically connected, while others are just aligned in our line of sight. Astronomers categorize double stars into two main types: binary stars and optical doubles. Binary stars are gravitationally bound and orbit each other, while optical doubles are not physically related and merely appear close together from our perspective. Studying double stars helps scientists learn about stellar masses, sizes, and the evolution of stars.