Astronomy Formulas

Essential astronomy and astrophysics formulas for orbital mechanics, stellar physics, and cosmology.

Estimate the number of detectable civilizations in the Milky Way. A framework for thinking about extraterrestrial life.

Calculate the minimum speed needed to escape a planet or star's gravitational pull. Essential for space travel calculations.

Hubble's law relates a galaxy's recession velocity to its distance. The foundation of the expanding universe model.

Kepler's third law relates a planet's orbital period to its distance from the star. Calculate orbits for any celestial body.

Calculate the speed needed to maintain a stable circular orbit around a planet, star, or other massive body.

Calculate the distance to nearby stars using the parallax angle. The most direct method for measuring stellar distances.

Calculate the event horizon radius of a black hole. Any mass compressed within this radius becomes a black hole.

Calculate a star's total energy output using the Stefan-Boltzmann law. Relates luminosity to radius and temperature.