säteisnopeusmenetelmä

The säteisnopeusmenetelmä, translated as the radial velocity method, is a technique used to detect exoplanets. It is one of the most successful methods for finding planets outside our solar system. The principle behind the method is based on observing the slight wobble of a star caused by the gravitational pull of an orbiting planet. As a planet orbits its star, its gravity tugs on the star, causing the star to move back and forth. This movement is too small to be seen directly, but it can be detected by measuring the Doppler shift in the star's light.

When a star moves towards an observer, its light is blueshifted (wavelengths become shorter). When it moves away, its light is redshifted (wavelengths become longer). By continuously monitoring the spectrum of a star, astronomers can detect these periodic shifts in wavelength. The amplitude of the wobble, and thus the magnitude of the Doppler shift, is proportional to the planet's mass and inversely proportional to the square of its orbital distance. The period of the wobble corresponds to the planet's orbital period.

The säteisnopeusmenetelmä is most effective at detecting massive planets that orbit close to their stars, as these produce the largest and most easily detectable wobbles. However, with increasingly sensitive instruments, it is becoming possible to detect smaller planets and those in wider orbits. This method has been instrumental in the discovery of thousands of exoplanets, providing crucial data for understanding planetary system formation and diversity.