Dopplermenetelmässä

Dopplermenetelmässä, often translated as the Doppler method, is a fundamental technique used in astronomy to detect exoplanets. It relies on the Doppler effect, the change in frequency of a wave in relation to an observer who is moving relative to the wave source. In the context of exoplanet detection, the wave source is a star, and the "observer" is an astronomer on Earth using a telescope and spectrograph.

When a planet orbits a star, its gravitational pull causes the star to wobble slightly. This wobble means the star is moving towards and away from Earth periodically. As the star moves towards us, the light it emits is blueshifted (its wavelength decreases). As it moves away, the light is redshifted (its wavelength increases). The Doppler method analyzes the star's light spectrum, looking for these tiny, periodic shifts in the absorption lines.

The magnitude of the Doppler shift is directly related to the velocity of the star. By observing these shifts over time, astronomers can infer the presence of an unseen companion, the exoplanet. The period of the wobble reveals the orbital period of the planet, and the amplitude of the wobble provides information about the planet's minimum mass. While this method is highly effective, it is most sensitive to massive planets orbiting close to their stars, as they induce larger and more easily detectable stellar wobbles. It is a radial velocity method because it measures the velocity of the star along the line of sight to the observer.