What Is Radial Velocity?

Radial velocity is a physics term that generally refers to the velocity component of the speed of the object in the direction of the observer's line of sight, that is, the projection of the velocity vector in the direction of the line of sight. Also called gaze velocity.

Radial velocity is a physics term that generally refers to the velocity component of the speed of the object in the direction of the observer's line of sight, that is, the projection of the velocity vector in the direction of the line of sight. Also called gaze velocity.

Chinese name

Radial velocity

Foreign name

radial velocity

Same concept

Gaze velocity

Definition

Projection of velocity vector in line of sight

Direction

Close to negative

Definition of radial velocity

Radial velocity is the component of the velocity of the target relative to the reference point on the line connecting the two.

Also known as gaze speed, that is, the speed of movement of an object or celestial body in the direction of the observer's line of sight. Generally refers to the velocity component of the object's moving speed in the direction of the observer's line of sight, that is, the projection of the velocity vector in the direction of the line of sight. Traditionally, a positive gaze speed indicates that the object is receding. If it is negative, the object is approaching.

The concept of radial velocity is mostly used in astrophysics and radar meteorology.

Radial velocity measurement principle

Radial velocity measurement is a method of indirectly detecting planets by measuring the disturbance of the planets to the stars. It is applicable to a wide range of detection objects. Therefore, compared with other exoplanet detection methods, apparent velocity measurements find the most exoplanets in the solar system. .

The basic principle of radial velocity measurement is shown in the figure on the right

Basic principles of radial velocity measurement

. When a planet orbits a star, its gravitational force acts on the star, causing the star to rotate around the common mass center M of the star and the planet. The velocity component of the star's motion in the observation direction, that is, the radial velocity, is a periodic signal determined by the planet's motion cycle, and its amplitude is determined by the mass of the star, the mass of the planet, the distance between the star and the planet, and the planetary orbital plane method. Parameters such as the angle between the line and the observation direction are determined.

For a sun-sized star, the magnitude of the radial velocity of the star is 12.7m / s when Jupiter moves at a distance of 5 AU; the magnitude of the radial velocity of the star is 1.5m / s when Neptune moves at a distance of AU; Super Earth (5 times the mass of the Earth) When moving at an AU distance, the magnitude of the star's radial velocity is 0.45m / s; while when the earth is moving at an AU distance, the magnitude of the star's radial velocity is only 9cm / s. This movement of a star will cause a Doppler shift in its spectrum. When the star moves to point A, the spectrum will blue shift; when the star moves to point B, the spectrum will red shift. The magnitude of the Doppler shift is directly related to the radial velocity. By observing the Doppler shift of the star spectrum, information about the planets can be obtained. ^[1]