Kepler's Third Law Calculator
Explore planetary orbits and calculate orbital periods with ease
About Kepler's Third Law Calculator
Kepler's Third Law of Planetary Motion, also known as the Law of Periods, is a fundamental principle in astronomy and celestial mechanics. This law, discovered by Johannes Kepler in the early 17th century, establishes a precise mathematical relationship between a planet's orbital period and its average distance from the sun.
The law states that the square of a planet's orbital period is directly proportional to the cube of the semi-major axis of its orbit. Mathematically, it's expressed as T² ∝ a³, where T is the orbital period and a is the semi-major axis of the orbit.
Our Kepler's Third Law Calculator simplifies the process of applying this principle. Whether you're a student studying astronomy, a space enthusiast, or a professional in the field, this tool allows you to quickly calculate either the orbital period or the semi-major axis of a planet's orbit.
To use the calculator, simply input either the semi-major axis (in Astronomical Units, AU) or the orbital period (in Earth years). The calculator will then compute the corresponding value based on Kepler's Third Law. This tool assumes that the central body's mass is significantly larger than the orbiting body's mass, which is typically the case for planets orbiting stars.
Remember, while this law was initially formulated for planets in our solar system, it applies to any object in orbit around a significantly more massive central body. This makes it a powerful tool for studying exoplanets, binary star systems, and even satellites orbiting Earth.
Frequently Asked Questions
What is Kepler's Third Law?
Kepler's Third Law states that the square of a planet's orbital period is directly proportional to the cube of the semi-major axis of its orbit. It's expressed as T² ∝ a³, where T is the orbital period and a is the semi-major axis.
What units does this calculator use?
This calculator uses Astronomical Units (AU) for the semi-major axis and Earth years for the orbital period.
Can this calculator be used for objects other than planets?
Yes, Kepler's Third Law applies to any object orbiting a significantly more massive central body, including exoplanets, moons, and artificial satellites.
What is the semi-major axis?
The semi-major axis is half the longest diameter of an elliptical orbit. For circular orbits, it's equal to the radius of the orbit.
How accurate is this calculator?
This calculator provides a good approximation based on Kepler's Third Law. However, it assumes a perfectly elliptical orbit and doesn't account for perturbations from other bodies or relativistic effects.