Using the Scientific Calculators
How to compute the numbers of astronomy yourself — orbital speeds and periods, stellar luminosities and lifetimes, distances from magnitudes, exoplanet temperatures, and telescope optics. Each calculator evaluates its published formula from real constants; every one is validated against a known result.
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- Scientific calculator
Escape Velocity
The minimum speed an object needs to break free of a body's gravity, ignoring drag. Set by the body's mass and radius alone.
- Scientific calculator
Orbital Period (Kepler's Third Law)
Kepler's third law: the time to complete one orbit, from the semi-major axis and the central mass. A planet at 1 AU around the Sun takes one year.
- Scientific calculator
Stellar Luminosity (Stefan–Boltzmann)
A star's total power output, from its radius and surface temperature by the Stefan–Boltzmann law. Doubling the temperature raises luminosity sixteenfold.
- Scientific calculator
Schwarzschild Radius
The radius of the event horizon of a non-rotating black hole of a given mass — the size to which that mass must be compressed to become one. The Sun's is just under three kilometres.