IAU Working Group Numerical Standards for Fundamental Astronomy

IAU Division I Working Group

Numerical Standards for Fundamental Astronomy

ASTRONOMICAL CONSTANTS

Welcome to the web page for the International Astronomical Union (IAU) Working Group (WG) on Numerical Standards for Fundamental Astronomy (NSFA). This WG was set up by a proposal adopted at the IAU General Assembly in 2006. The stated goals of the proposed WG:

Update the IAU system of astronomical constants with the current Best Estimates
Conform with IAU Resolutions/IERS Conventions/SI

The NSFA WG pages are being maintained by IAU Commission A3: Fundamental Standards .

News ...

2020 November: New Triennial Report Added:

The 2019-2021 Triennial Report is now availble on this page.

2020 April: NSFA Website Update:

NSFA Website now incorporated as an extension of the Commission A3 website

Defining Constants now featured on standalone page to distinguish from Best Estimates

Constant for Potential of Geoid updated

2012 August: AU Updated. IAU Resolution B2 recommends:

that the astronomical unit be re-defined to be a conventional unit of length equal to 149 597 870 700 m exactly, in agreement with the value adopted in IAU 2009 Resolution B2

that this definition of the astronomical unit be used with all time scales such as TCB, TDB, TCG, TT, etc.

the Gaussian gravitational constant k be deleted from the system of astronomical constants

the value of the solar mass parameter, GMS, be determined observationally in SI units

that the unique symbol “au” be used for the astronomical unit

2011 July: WG Report Published

The report of this WG that lists the IAU 2009 System of Astronomical Constants together with all the detailed notes and explanations has been published in Celestial Mechanics and Dynamical Astronomy under Open Access. Open Access permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.

2011 May: Updated

The pages with the IAU 2009 constants have finally been aligned and corrected to agree with the Report to be published in Celestial Mechanics and Dynamical Astronomy. Until the Current Best Estimates require updating they are in agreement with the IAU 2009 Constants.

2011 February 16: New web pages adopted

The new NFSA web pages have now been adopted as the official pages.

2010 September 19 Journees 2010

The Working Group meet after the Journees at the Paris Observatory. At the meeting procedures for the adoption new best estimates was discussed. A proposal concerning the definition of the astronomical unit was considered.