Microarcsecond instability of the celestial reference frame

• Published in: Monthly notices of the Royal Astronomical Society Vol. 300; no. 1; pp. 287 - 291
• Main Authors: Sazhin, M. V., Zharov, V. E., Volynkin, A. V., Kalinina, T. A.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 11-10-1998
• Subjects: astrometry; gravitational lensing; quasars: general; reference systems; gravitational lensing; quasars: general; astrometry; reference systems
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1046/j.1365-8711.1998.01908.x

The fluctuation of the angular positions of reference extragalactic radio and optical sources under the influence of the irregular gravitational field of visible Galactic stars is considered. It is shown that these angular fluctuations range from a few up to hundreds of microarcseconds. This leads to a small rotation of the celestial reference frame. The non-diagonal coefficients of the rotation matrix are of the order of a microarcsecond. The temporal variation of these coefficients due to the proper motion of the foreground stars is of the order of one microsecond per 20 years. The celestial reference frame can therefore be considered inertial and homogeneous only to microarcsecond accuracy. Astrometric catalogues with microarcsecond accuracy will be unstable, and must be re-established every 20 years.