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The square of the orbital period $T$ of a planet is directly proportional to the cube of the semi-major axis $a$ of its orbit, represented by the equation $T^2 = k a^3$, where $k$ is a constant. This law, also known as the Harmonic Law, relates the distance of a planet from the Sun to its orbital period.

The differential gravitational force experienced by an object which is in the gravitational field of another body, leading to stretching along the axis pointing towards the massive body. It is responsible for phenomena such as ocean tides on Earth.

A parameter that determines the amount by which its orbit around another body deviates from a perfect circle. An eccentricity of 0 corresponds to a circular orbit, values between 0 and 1 represent an elliptical orbit.

The center of mass of two or more bodies that are orbiting each other, which is the point about which they both orbit. For some planet-moon systems, this point can lie outside of the primary body (e.g., the Earth-Moon system).

The time required for a celestial object to reoccupy its same position in the sky relative to the Sun as observed from Earth. This period differs from the sidereal period due to Earth's own orbit around the Sun.

A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time. This law, also known as the Law of Equal Areas, implies that planets have varying speeds along their orbit.

An elliptical orbit used to transfer between two circular orbits of different radii in the same plane and around the same central body via two engine impulses. This transfer is the most fuel-efficient method of traveling between the two orbits.

An orbit around Earth with an orbital period that matches Earth's rotation on its axis, which takes one sidereal day (approximately 23.93 hours). A subset of geosynchronous orbits is the geostationary orbit, which remains fixed with respect to a point on the Earth.

The time taken by a celestial object to orbit another object relative to the fixed stars. For Earth, this is about 23.93 hours. It differs from the synodic period, which is measured relative to the Sun.

All planets move in elliptical orbits, with the sun at one focus. This law, also known as the Law of Ellipses, describes the shape of the orbit.

Every point mass attracts every other point mass by a force acting along the line intersecting both points. The force is proportional to the product of their masses and inversely proportional to the square of the distance between their centers: $F = G \frac{m_1 m_2}{r^2}$, where $G$ is the gravitational constant.

The minimum distance to which a large satellite can approach its primary body without being torn apart by tidal forces. It is dependent on the density of the satellite and the mass of the primary body.

The minimum speed needed for an object to break free from the gravitational attraction of a massive body without further propulsion. It's given by the equation $v_e = \sqrt{\frac{2GM}{r}}$, where $G$ is the gravitational constant, $M$ is the mass of the body being escaped from, and $r$ is the distance from the center of the body to the object.

Points in space where the gravitational forces of a two-body system like Earth and the Sun produce enhanced regions of attraction and repulsion, which can be used to position spacecraft. These points are labeled L1 through L5.