Radial Velocity

The Radial Velocity of an object is the speed at which the object is moving along the user's line-of-sight, i.e., away from or towards the camera. This property is read-only and calculated automatically by Universe Sandbox.

This property can be used to simulate the common exoplanet detection technique known as Doppler spectroscopy or simply the "radial velocity method". In this method, astronomers measure shift in the wavelengths of light coming from a star, and use this information to calculate the star's radial velocity. An exoplanet orbiting at the right angle relative to the observer will cause the star to move slightly towards and away from the telescope as the star orbits their barycenter, causing a variation in the radial velocity over time. In Universe Sandbox, the user can simulate this technique by using the Graph option for the Radial Velocity property.

Location
The Radial Velocity property is located in the Camera Relative section of the Motion tab of an object's properties panel.

Units
Radial Velocity can be viewed or edited using the following properties:
 * The Speed of Light (lightspeed) = 2.99792458×108 m/s
 * Kilometers per Second (km/s) = 1000 m/s
 * Meters per Second (m/s) is the SI unit for speed
 * Kilometers per Hour (km/h) = 0.2778 m/s

Unlike the Speed property, which can only be positive, Radial Velocity can be positive (indicating that the object is moving away from the camera) or negative (indicating that the object is moving towards the camera).