International Celestial Reference System
The International Celestial Reference System ( ICRS ) or International sky reference system is the internationally agreed, global reference system of Cartesian coordinates of the solar system . Its origin is the barycentre (center of mass) of the solar system. The axes are defined by the celestial reference pole and the vernal equinox , the mean position of which is determined by directional relationships to extraterrestrial targets.
In the IAU's Fundamental Catalog 5 (FK5) , the system of celestial coordinates is implemented through continuous long-term observation of the mean locations of 1535 fundamental stars for the epoch J2000.0 .
By determining the coordinates of 608 extragalactic radio sources, a specific reference frame for the ICRS is created, the International Celestial Reference Frame (ICRF). With Gaia DR2 , the positions of more than half a million quasars were measured, which in the Gaia Celestial Reference Frame 2 (GCRF2) form their own reference frame in the optical field.
The orientation parameters of the earth in relation to the stars and other geophysical data are provided by the International Service for Earth Rotation and Reference Systems (IERS).
literature
- Arias, EF; Charlot, P .; Feissel, M .; Lestrade, J.-F .: The extragalactic reference system of the International Earth Rotation Service, ICRS. In: Astronomy and Astrophysics . tape 303 , November 1995, pp. 604-608 , bibcode : 1995A & A ... 303..604A ( harvard.edu [PDF]).
- RK Bachchan, D. Hobbs, L. Lindegren: Gaia reference frame amid quasar variability and proper motion patterns in the data . Ed .: Astronomy & Astrophysics. v.2 edition. June 2, 2016, doi : 10.1051 / 0004-6361 / 201527935 , arxiv : 1512.08917 .
Web links
Homepage of the IERS (English)