The International Celestial Reference Frame (ICRF) is a quasi-inertial reference frame centered at the barycenter of the Solar System, defined by the measured positions of 212 extragalactic sources (mainly quasars). Although relativity implies that there is no true inertial frame, the extragalactic sources used to define the ICRF are so far away that any angular motion is essentially zero. The ICRF is now the standard reference frame used to define the positions of the planets (including the Earth) and other astronomical objects. It has been adopted by International Astromical Union since 1st January 1998.
Note that, in astrometry, a reference frame is the physical realization of a reference system, i.e., the reference frame is the reported coordinates of datum points. The ICRF is the realization of the International Celestial Reference System, and agrees with the orientation of the Fifth Fundamental Catalog (FK5) "J2000.0" frame to within the (lower) precision of the latter.
Famous quotes containing the words celestial, reference and/or frame:
“He all their ammunition
And feats of war defeats
With plain heroic magnitude of mind
And celestial vigour armed;”
—John Milton (16081674)
“If we define a sign as an exact reference, it must include symbol because a symbol is an exact reference too. The difference seems to be that a sign is an exact reference to something definite and a symbol an exact reference to something indefinite.”
—William York Tindall (19031981)
“Human life itself may be almost pure chaos, but the work of the artistthe only thing hes good foris to take these handfuls of confusion and disparate things, things that seem to be irreconcilable, and put them together in a frame to give them some kind of shape and meaning. Even if its only his view of a meaning. Thats what hes forto give his view of life.”
—Katherine Anne Porter (18901980)