An elliptical orbit is an orbital path that an object, such as a planet or a satellite, takes around a central body, such as a star or a planet. It is called an elliptical orbit because the shape of the orbit is an ellipse, rather than a circle.
An elliptical orbit has two points of special significance, called the periapsis and the apoapsis. The periapsis is the point where the orbiting object is closest to the central body, and the apoapsis is the point where it is farthest away. The distance between the periapsis and the apoapsis is known as the major axis of the ellipse, and the center of the ellipse is known as the focus.
The gravitational force of the central body causes the object to follow an elliptical path rather than a circular one. The object will move faster as it approaches the periapsis, and slower as it moves away from the periapsis towards the apoapsis.
Elliptical orbits are common in the solar system, with all the planets orbiting the sun in elliptical orbits. It is also common in other stellar systems and galaxies, where celestial bodies orbits around their host star or galaxy in elliptical orbits.
This type of orbit is first described by Johannes Kepler in the early 17th century, who also formulated the three Kepler's laws of planetary motion, which explains the behavior of objects in elliptical orbits.