B. Guinot

Proposed terminology in fundamental astronomy based on IAU 2000 resolutions

We present the proposals of the IAU Division I Working Group on Nomenclature for Fundamental Astronomy (NFA) that was formed at the IAU XXV General Assembly in 2003.

Systèmes de référence en astronomie

Dynamical theories imply the existence of reference systems in time and space. When applied to physical systems, these theories require physical representations of the references: realized time scales and reference frames. We review recent developments in such realizations matching the quality of modern observations. Whereas international atomic time (TAI), in existence since 1955, is the basis of quasi-ideal representations of time coordinates needed in dynamics, the problem of realizing a non-rotating spatial reference remained critical until recently. The modern solution appeared in the 1970s with the astrometric application of very long baseline radio-interferometry (VLBI), which allows us to tie the orientation of the celestial frame to the directions of the most distant bodies we know, the quasars. Improvements in this technique as well as the realization of the optical counterpart of the celestial radio frame, thanks to the success of the astrometric mission Hipparcos, allowed the adoption of a new conventional celestial reference frame that will become official from 1 January 1998. The old dream of an absolute reference for measuring the angular motion of celestial bodies has become a reality. This opens a new era for fundamental astronomy and for astrophysics.

DIVISION I / WORKING GROUP NOMENCLATURE FOR FUNDAMENTAL ASTRONOMY

The IAU Division I Working Group on Nomenclature for Fundamental Astronomy (NFA) was established by the IAU XXV General Assembly with the task of providing proposals for new nomenclature associated with the implementation of the IAU XXIV GA resolutions (2000) and to make related educational efforts for bringing the issue to the notice of scientists in the community.

Division I Working Group on “Nomenclature for Fundamental Astronomy” (NFA)

The IAU Division 1 Working Group on “Nomenclature for Fundamental Astronomy” (NFA) was established by the 25th IAU General Assembly with the task of providing proposals for new nomenclature associated with the implementation of the IAU 2000 resolutions and to make related educational efforts for bringing the issue to the notice of scientists in the community. A meeting of this working group was organized during the 26th IAU GA in order to adopt the final conclusions of the WG and to discuss the status of the WG resolutions proposals to the IAU before they were discussed at the Division 1 meetings and then submitted to the IAU GA at its second meeting (24 August). This WG meeting was also an opportunity to discuss the final scheme and content of the NFA explanatory document, as well as the plan for publication of the NFA recommendations and of the NFA explanatory document. The future diffusion of the NFA educational documents was also discussed. Finally, a list of scientific issues were identified by the NFA WG to be proposed to Division 1 as topics for its proposed new WGs. Ten out of fifteen WG members participated in this NFA WG meeting. A few other participants, not belonging to the WG, were invited to attend the meeting, including the upcoming Division 1 president, Jan Vondrak.