Space velocity

Definition

Space velocity is the actual velocity of a star or other celestial object relative to the Sun. It consists of both radial and tangential components.

5 Must Know Facts For Your Next Test

1. Space velocity combines both the radial velocity (toward or away from Earth) and tangential velocity (perpendicular to our line of sight).
2. It can be calculated using the Pythagorean theorem if both radial and tangential velocities are known.
3. Astronomers use Doppler shifts in spectra to measure the radial component of space velocity.
4. Proper motion measurements help determine the tangential component of a star's space velocity.
5. Space velocity helps in understanding the dynamics and kinematics of stars within galaxies.

Review Questions

• What components make up a star's space velocity?
• How do astronomers measure the radial component of space velocity?
• Why is knowing a star's space velocity important in astronomy?

Related terms

Radial Velocity: The component of an object's velocity directed along the line of sight toward or away from an observer.

Tangential Velocity: The component of an object's motion perpendicular to our line of sight, measured in arcseconds per year.

Doppler Shift: A change in frequency or wavelength observed when a source moves relative to an observer, used to measure radial velocities.