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Published online by Cambridge University Press: 05 November 2011
Preliminary remark. The numbers that are given in this appendix should not be considered as reference values. Although the present authors have tried to provide numbers that are as close as possible to what is estimated to be the best values, they do not guarantee either that they are the best possible, or that all are mutually consistent. In several cases, authorities that publish values of astronomical constants do not agree, and the choice of one or the other is necessarily subjective. Furthermore, as time goes on, better values will become available. For these reasons, we do not associate uncertainties to values, and one should consider these lists as providing orders of magnitude of the parameters and not as a basis for accurate and dependable calculations.
IAU system of astronomical constants, best estimates
SI units
The units meter (m), kilogram (kg), and second (s) are the units of length, mass and time in the International System of Units (SI).
Astronomical units
The astronomical unit of time is a time interval of one day (D) of 86 400 seconds. An interval of 36 525 days is one Julian century.
The astronomical unit of mass is the mass of the Sun (S).
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