Circular orbit

A circular orbit is a trajectory around a central body at constant distance from its center. In an ideal two-body system, gravity supplies the centripetal acceleration needed to maintain it.

Gravitational force: The mutual attraction between masses, described by Newton’s law of universal gravitation. It supplies the inward acceleration that continually bends an orbiting body's path.
Orbital radius: The distance from an orbiting object's central body or chosen orbital center. Its unchanging value defines the circular shape of the orbit.
Geostationary orbit: A circular equatorial orbit in which a satellite remains fixed over one point on Earth's surface. It is a specialized circular orbit chosen to match Earth's rotation.
Elliptical orbit: An orbit shaped as an ellipse, with the central body at one focus and varying orbital distance. It is the general bound Keplerian orbit; a circle is its zero-eccentricity limit.
Kepler's third law: The law that relates an orbit's period squared to its semimajor axis cubed around a given central mass. For a circle, the semimajor axis is the constant orbital radius.
Centripetal force: The inward net force required to keep an object moving along a curved path. Gravity acts as this inward force in an ideal circular orbit.
Orbital period: The time an orbiting object takes to complete one revolution. For a circular orbit, its value follows from radius and the central body's mass.
Low Earth orbit: An Earth-centered orbit with altitude generally below about 2,000 kilometers. Many spacecraft use near-circular paths in this altitude region.
Parabolic trajectory: An ideal gravitational trajectory with zero orbital energy and eccentricity equal to one. Unlike a circular orbit, it is an unbound escape path rather than a closed orbit.
Specific orbital energy: An orbiting body's mechanical energy per unit mass in a gravitational field. Its value for a circular orbit depends only on radius and the central body's gravitational parameter.

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