Definition

1. Noun:
   • A system of two stars that revolve around each other under their mutual gravitation: A "double star" is a pair of stars that appear close together in the sky and are physically connected by gravity, orbiting a common center of mass.

Usage

• The term "double star" is used in astronomy to describe a binary star system. It is important to distinguish it from stars that merely appear close together from our viewpoint but are not gravitationally bound (which are called "optical doubles").

Examples

• Noun:
  • Through the telescope, we observed a beautiful double star in the constellation Cygnus.
  • Astronomers study double stars to understand stellar masses and orbits.

Advanced Usage

• "Visual double star": A pair of stars that can be seen as separate through a telescope.

  • Albireo is a famous visual double star, with components of contrasting colors.

• "Spectroscopic double star": A pair of stars so close they can only be distinguished by analyzing their combined light spectrum.

  • The star was identified as a spectroscopic double star after detailed spectral analysis.

Variants and Related Words

• Binary star: A more precise synonym for a gravitationally bound double star system.

  • A binary star is a type of double star.

• Optical double: Two stars that appear close together in the sky by chance but are not gravitationally related.

  • That pair is merely an optical double, not a true double star system.

Synonyms

• Binary star: A system of two stars orbiting each other.
• Binary system: A general term for any system of two objects orbiting a common center of mass, often used for stars.

Related Phrases

• "Eclipsing binary": A type of double star where, from Earth, one star periodically passes in front of the other, causing a dip in brightness.

  • Algol is a well-known eclipsing binary.

• "Close binary": A double star system where the two stars are very near to each other.

  • In a close binary, material can transfer from one star to the other.

Noun

1. a system of two stars that revolve around each other under their mutual gravitation