Lähikohtaamispisteen

Lähikohtaamispisteen is a Finnish term that translates to "point of closest approach" or "periapsis" in English. It refers to the point in the orbit of a celestial body where it is nearest to the body it orbits. For example, in Earth's orbit around the Sun, the point of closest approach is called perihelion. Similarly, in the Moon's orbit around the Earth, this point is known as perigee.

The concept of lähikohtaamispisteen is fundamental in orbital mechanics. It is a key parameter used to describe an elliptical orbit, along with the apoapsis (the point farthest from the central body). The distance at the lähikohtaamispisteen and the apoapsis, along with the orbital period, define the shape and size of the orbit.

Understanding the lähikohtaamispisteen is important for various applications, including space mission planning, calculating gravitational interactions, and predicting the positions of celestial objects. For instance, spacecraft trajectories are carefully calculated to account for their lähikohtaamispisteen relative to planets or other celestial bodies to achieve desired maneuvers or rendezvous. The gravitational forces are strongest at this point, influencing the spacecraft's velocity and trajectory significantly. Astronomers also use this concept to study the dynamics of star systems and galaxies.