The Secular Aberration Drift and Future Challenges for VLBI Astrometry

Understand

The centrifugial acceleration of the Solar system, resulting from the gravitational attraction of the Galaxy centre, causes a phenomenon known as 'secular aberrration drift'.

• This acceleration of the Solar system barycentre has been ignored so far in the standard procedures for high-precision astrometry.
• It turns out that the current definition of the celestial reference frame as epochless and based on the assumption that quasars have no detectable proper motions, needs to be revised.
• In the future, a realization of the celestial reference system (realized either with VLBI, or GAIA) should correct source coordinates from this effect, possibly by providing source positions together with their proper motions.