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Astrodynamic Parameters

This page contains selected parameters commonly used in astrodynamic computations. References are listed below.

Parameter Symbol Value Reference
day d 86400 s
Julian year y 365.25 d 1. (see below)
Julian century Cy 36525 d 1. (see below)
speed of light in vacuum c 299792458 m/s 2018 CODATA recommended values
astronomical unit au 149597870700 m IAU 2012 Resolution B1
mean sidereal day 86164.09054 s [ 23:56:04.09054 ] 1. (see below)
sidereal year (quasar ref. frame) 365.25636 d
Newtonian constant of gravitation G 6.67430 (± 0.00015) x 10-11 kg-1 m3 s-2 2018 CODATA recommended values
general precession in longitude 5028.83 (± 0.04) arcsec/Cy
obliquity of ecliptic (J2000) ε 84381.412 (± 0.005) arcsec 2. (see below)
obliquity of ecliptic (J2000) [IAU 1976] ε 84381.448 arcsec 3. (see below)
light time for 1 au ΤA au/c = 499.004783836 s
heliocentric gravitational constant GMsun 1.32712440018 x 1020 (± 8 x 109) m3 s-2

Planetary Masses

These data are from the JPL planetary ephemeris DE440 (ref. 4, below).

Planet GM (km3 s-2)
Mercury 22031.868551
Venus 324858.592000
Earth 398600.435507
Moon 4902.800118
Mars system 42828.375816
Jupiter system 126712764.100000
Saturn system 37940584.841800
Uranus system 5794556.400000
Neptune system 6836527.100580
Pluto system 975.500000

Notes

References

  1. Seidelmann, P. K. (Ed.), 1992, “Explanatory supplement to the Astronomical Almanac”, University Science Books

  2. Standish, E.M., 1995, “Report of the IAU WGAS Sub-Group on Numerical Standards”, in Highlights of Astronomy (I. Appenzeller, ed.), Table 1, Kluwer Academic Publishers, Dordrecht.

  3. Lederke, T, 1980, “The IAU (1976) System of Astronomical Constants”, Astronomische Gesellschaft…, 48:59:65.

  4. Park, R.S., et al., 2021, “The JPL Planetary and Lunar Ephemerides DE440 and DE441”, Astronomical Journal, 161:105.