IAU Division 1 Working Group
Numerical Standards for Fundamental Astronomy
ARCHIVE : Superseded Best Estimates


Below is the list of previous defining constants and IAU Best Estimates that have been superseded.


2009 Gaussian Grav. Astronomical Unit Heliocentric Grav.

The List of Superseded Constants and Estimates - SI Units

 
Gaussian gravitation constant k = 1.720 209 895 x 10−2 k
Change:
  • IAU GA 2012, Resolution B2, defined the au as fixed value and stated that k be deleted from the system of constants and solar mass parameter (previousl called the heliocentric gravitational constant), GMS, be determined observationally in SI units.
  • The block is the previous definition, notes and references.
Status:
  • Auxiliary defining constant.
  • IAU 2009 adopted constant.
  • Adopted CBE 2009 August 10.
Notes:
  1. The Gaussian gravitational constant, k, is listed as an auxiliary defining constant as it continues to be used to define the relationship between the astronomical unit and GMS. This value from the IAU 1976 System of Astronomical Constants is retained here and has been used to derive the GMS value. However, other estimates of GMS can be determined directly by to fitting modern planetary ephemerides (e.g. INPOP08, DE423, EPM2008) observations.
  2. The Gaussian gravitation constant remains a defining constant of the IAU and was used to derive the value of au that is given (Pitjeva and Standish, 2009). For users who need a consistent value for the heliocentric gravitational constant, k should also be used to derive GMS through the equation au3 k2 / D2 = GMS where D is the time interval of one day of 86400 s. Note that estimates can now be determined directly by fitting modern planetary ephemerides to observations.
  3. There is a difference in opinion regarding the use of k. Some would use k in the traditional way along with a measured astronomical unit, au, to calculate the heliocentric gravitation constant, GMS. Others believe that au should become a defining constant, which would fundamentally change the status of k. Although k has been retained to be consistent with historical systems, it is expected that a recommendation will be discussed at the 2012 IAU General Assembly that will resolve this issue.
References:
  1. International Astronomical Union (IAU), 1976, "Proceedings of the Sixteenth General Assembly," Transactions of the IAU, XVIB, p. 31, pp. 52-66.
  2. Gauss, C.F., 1857, Theory of the Motion of the Heavenly Bodies Moving About the Sun in Conic Sections, Boston: Little, Brown and Company, p. 2.
  3. Pitjeva, E.V. and Standish, E.M., 2009, "Proposals for the masses of the three largest asteroids, the Moon-Earth mass ratio and the astronomical unit," Celest. Mech. Dyn. Astr., 103, pp. 365-372, doi: 10.1007/s10569-009-9203-8.
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Astronomical unit au = 1.495 978 707 00 x 1011 m au
Uncertainty: 3 m
Change:
  • IAU GA 2012, Resolution B2, defined the astronomical unit to be a fixed number of kilometres.
  • The block is the previous definition, notes and references.
Status:
  • Other constant.
  • IAU 2009 adopted constant.
  • Adopted CBE 2009 August 10.
Notes:
  1. The value for the astronomical unit is TDB-compatible.
  2. An accepted definition for the TCB-compatible value of the au is still under discussion.
  3. The current best estimate for the astronomical unit, au, has been taken from Pitjeva and Standish (2009) and is an average of recent estimates for the au defined by k.
References:
  1. Pitjeva, E.V. and Standish, E.M., 2009, "Proposals for the masses of the three largest asteroids, the Moon-Earth mass ratio and the astronomical unit," Celest. Mech. Dyn. Astr., 103, pp. 365-372, doi: 10.1007/s10569-009-9203-8.
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Heliocentric gravitational constant GMS = 1.327 124 420 99 x 1020 m3s−2 [TCB-compatible]
GMS = 1.327 124 400 41 x 1020 m3s−2 [TDB-compatible]		 GMS
Uncertainty: 1.0 x 1010 m3s−2 [TCB-compatible]
1.0 x 1010 m3s−2 [TDB-compatible]
Change:
  • IAU 2012 GA Resolution B2 recommends that this constant, the heliocentric gravitational constant, be renamed the solar mass parameter and that it be determined observationally in SI units.
  • The block is the previous definition, notes and references.
Status:
  • Body constant.
  • IAU 2009 adopted constant.
  • Adopted CBE 2009 August 10.
Notes:
  1. To adhere with historical definitions, the value for GMS should be consistent with the au using the equation GMS = au3 k2 / D2.
  2. The value for GMS given is taken from the Folkner et al. (2008) fit to the DE421 ephemerides. It was not derived using the value of au, but the TDB-compatible value of GMS given is consistent with the value of au given (Pitjeva and Standish, 2009) to within the errors of the estimate.
  3. Since it is now possible to estimate directly a value for GMS, it is expected that a recommendation will be discussed at the 2012 IAU General Assembly to change the historical relationship between GMS, k, and au.
References:
  1. Folkner, W.M., Williams, J.G., and Boggs, D.H., 2008, "The Planetary and Lunar Ephemeris DE 421," Memorandum IOM 343R-08-003, 31 pp.
  2. Pitjeva, E.V. and Standish, E.M., 2009, "Proposals for the masses of the three largest asteroids, the Moon-Earth mass ratio and the astronomical unit," Celest. Mech. Dyn. Astr., 103, pp. 365-372, doi: 10.1007/s10569-009-9203-8.
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Ratio of the mass of the Sun to Mercury MS/MMe = 6.0236 x 106 MS/MMe
Uncertainty: 3 x 102
Change:
  • 2015 July NSFA WG recommends that this value be replaced by a more modern value.
Status:
  • Body constant.
  • IAU 2009 adopted constant.
  • Adopted CBE 2009 August 10.
References:
  1. Anderson, J.D., Colombo, G., Esposito, P.B., Lau, E.L., and Trager, G.B., 1987, "The Mass Gravity Field and Ephemeris of Mercury," Icarus, 71, pp. 337-349.
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Ratio of the mass of the Sun to Uranus MS/MU = 2.290 298 x 104 MS/MU
Uncertainty: 3 x 10−2
Change:
  • 2015 July NSFA WG recommends that this value be replaced by a more modern value.
Status:
  • Body constant.
  • IAU 2009 adopted constant.
  • Adopted CBE 2009 August 10.
Notes:
  1. Includes the sum of the masses of the body and its satellites.
References:
  1. Jacobson, R.A., Campbell, J.K., and Taylor, A.H., 1992, "The Masses of Uranus and its Major Satellites from Voyager Tracking Data and Earth-based Uranian Satellite Data," Astron. J., 103(6), pp. 2068-2078.
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Ratio of the mass of the Sun to (134340) Pluto MS/MP = 1.365 66 x 108 MS/MP
Uncertainty: 2.8 x 104
Change:
  • 2015 July NSFA WG recommends that this value be replaced by a more modern value.
Status:
  • Body constant.
  • IAU 2009 adopted constant.
  • Adopted CBE 2009 August 10.
Notes:
  1. Includes the sum of the masses of the body and its satellites.
  2. Equivalently MP/MS = 7.322 47 x 10−9 ± 0.001 50 x 10−9.
References:
  1. Tholen, D.J., Buie, M.W., and Grundy, W., 2008, "Masses of Nix and Hydra," Astron. J., 135(3), pp. 777-784.
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Ratio of the mass of (4) Vesta to the Sun MVesta/MS = 1.35 x 10−10 MVesta/MS
Uncertainty: 3 x 10−12
Change:
  • 2015 July NSFA WG recommends that this value be replaced by a more modern value.
Status:
  • Body constant.
  • IAU 2009 adopted constant.
  • Adopted CBE 2009 August 10.
References:
  1. Pitjeva, E.V. and Standish, E.M., 2009, "Proposals for the masses of the three largest asteroids, the Moon-Earth mass ratio and the astronomical unit," Celest. Mech. Dyn. Astr., 103, pp. 365-372, doi: 10.1007/s10569-009-9203-8.
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