An object's orbital period can be computed from its semi-major axis and the mass of the body it orbits using the following formula:
- a is the semi-major axis of the object
- P is the orbital period
- G is the gravitational constant
- M is the mass of the parent body
|Default units||Acceptable substitute units|
|a||meters (m)||centimeters (cm), kilometers (km), miles (mi), feet (ft), Earth radii (Re), Solar radii (Rs), astronomical units (AU), light years (ly), parsec (pc)
|T||seconds (s)||minutes (m), hours (h), days (d), years (yr)|
|M||kilograms (kg)||grams (g), Earth masses (Me), Solar masses (Ms)|
1. A satellite orbits the Earth. It's semi-major axis is 7000 km. What is the satellite's orbital period in hours?
2. Astronomers discover a distant planet orbiting the Sun. It's semi-major axis is 1 light year. What is the planet's orbital period in years?
Enter 7000 km for a and 1 Me for M.|
The calculator gives you an answer of 5830.318 s.
Highlight the s and type h. It now gives you an answer of 1.6195 hr.
Enter 1 LY for a and 1 Ms for M.|
The calculator gives you an answer of 501850205474964.06 s.
Highlight the s and type y. It now gives you an answer of 15902421.421915896 yr.