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Calcimator

Binary Star Orbit

Calculate the total mass of a binary star system from orbital period and semi-major axis using Kepler's Third Law.

Inputs

years
AU

Results

Total System Mass

1 M☉

Orbital Velocity

29.79 km/s

Each Star (if equal)0.5 M☉
Period365.25 days
Separation499 light-sec
Orbital Energy-443,669,318.18
How to Use This Calculator
  1. Enter the Orbital Period (years) of the binary system — obtainable from long-term radial velocity or astrometric monitoring.
  2. Enter the Semi-Major Axis (AU) of the relative orbit, derived from angular separation at known distance or interferometry.
  3. Read Total System Mass (M☉) computed via Kepler's Third Law (M = a³/P²).
  4. If the stars have equal mass, Each Star mass is half the total; use the mass ratio from spectroscopy for unequal pairs.
  5. Use Orbital Velocity (km/s) and Separation (light-sec) to contextualize the system's compactness.
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Formula

M = a³ / P² (Kepler's Third Law)

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