2. Astrophysical constants 1 2. ASTROPHYSICAL CONSTANTSANDPARAMETERS

values give the one-standard deviation uncertainties in the last digit(s). Physical constants are from Ref. 1. While every effort has been made to obtain the most accurate current values of the listed quantities, the table does not represent a critical review or adjustment of the constants, and is not intended as a primary reference. The values and uncertainties for the cosmological parameters depend on the exact data sets, priors, and basis parameters used in the fit. Many of the parameters reported in this table are derived parameters or have non-Gaussian likelihoods. Their error bars may be highly correlated with other parameters and care must be taken when extrapolating to higher significance levels. In most cases we report the best fit of a spatially-flat ΛCDM cosmology with a power-law initial spectrum to WMAP3 data alone [2]. For more information see Ref. 3 and the original papers. Quantity Symbol, equation Value Reference, footnote speed of light c 299 792 458 m s−1 defined[4] Newtonian gravitational constant GN 6.6742(10) × 10−11 m3 kg−1 s−2 [1, 5] astronomical unit (mean Earth-Sun distance) AU 149 597 870 660(20) m [6, 7] tropical year (equinox to equinox) (2005.0) yr 31 556 925.2 s [6] sidereal year (fixed star to fixed star) (2005.0) 31 558 149.8 s [6] mean sidereal day (2005.0) 23h 56m 04.s090 53 [6