Lähentymisnopeus

Lähentymisnopeus, or radial velocity in English, is the component of the relative velocity of two objects that lies along the line connecting them. It measures how quickly the distance between two objects is changing. A positive lähentymisnopeus indicates that the objects are moving away from each other, while a negative lähentymisnopeus signifies that they are moving closer together.

In astronomy, lähentymisnopeus is a fundamental quantity used to study the motion of celestial bodies. It is measured using the Doppler effect, which causes the light emitted or reflected by an object to shift in frequency depending on its radial velocity relative to the observer. If an object is moving towards an observer, its light will be blueshifted (shifted to shorter wavelengths), and if it is moving away, its light will be redshifted (shifted to longer wavelengths).

The measurement of lähentymisnopeus has been crucial in many astronomical discoveries. For instance, it was used by Edwin Hubble to discover the expansion of the universe, as he observed that distant galaxies were predominantly redshifted, indicating they were moving away from us. It is also used to detect exoplanets orbiting other stars. When an exoplanet orbits a star, it causes the star to wobble slightly. This wobble results in a periodic change in the star's lähentymisnopeus, which can be detected by instruments. Furthermore, lähentymisnopeus is vital in understanding the dynamics of star clusters, galaxies, and the distribution of dark matter in the universe.