Measuring this quantity for water masers associated with galactic centers makes it possible to directly determine the distance to the galaxy.
In 1996, Eckart and Genzel used speckle interferometry to measure this quantity and found that its distribution is centered on the purported position of Sagitarius A-star. Measuring this quantity for water masers associated with galactic centers makes it possible to directly determine the distance to the galaxy. Surveys for measuring this quantity typically use faint galaxies to define the reference frame, and in addition to measuring parallax, the precise measurement of this quantity was the major goal of the Hipparcos satellite. Typically measured in arcseconds per year, for 10 points, identify this astrometric quantity which measures the change of position of an object on the celestial sphere, factoring out change-of-coordinates phenomena such as precession.
In 1996, Eckart and Genzel used speckle interferometry to measure this quantity and found that its distribution is centered on the purported position of Sagitarius A-star.
proper motion