Binary Star

Types of Binary Star Systems

  • Visual binary
    • A binary star system where both stars can be seen with a telescope
  • Spectroscopic binary

Masses of Binary Star Systems

  • Can be estimated using Isaac Newton's reformulation of Johannes Kepler's third law of planetary motion
    • If two objects are in mutual revolution, then the period ($P$) with which they go around each other is related to the semi-major axis ($D$) of the orbit of one with the respect to the other
    • $D^3 = (M_1 + M_2)P^2$
      • $D$ is in astronomical units
      • $P$ is measured in years
      • $M_1 + M_2$ is the sum of the masses of the two stars in units of the Sun's mass

Star Astronomy