Selected Astronomical Constants, 2018

This is the ASCII version of pages K6K7 of The Astronomical Almanac 2018. The following nomenclature is used in this file:
(a) greek letters, as in TeX, are spelt out, e.g., alpha,
(b) the symbols ^ and _ are used (as in TeX) to indicate superscripts and subscripts, respectively,
(c) the symbols *, / and +/ denote multiplication, division, and plusminus uncertainty bounds, respectively, and
(d) numerical exponents are given with the Fortran D format.
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 The IAU 2009 System of Astronomical Constants (1) as published in the Report of the IAU Working Ground on Numerical Standards 
 for Fundamental Astronomy (NSFA, 2011), and updated by resolution B2 of the IAU XXVIII General Assembly (2012), (2) planetary 
 equatorial radii, taken from the report of the IAU WG on Cartographic Coordinates and Rotational Elements: 2009 (2011), and 
 lastly (3) other useful constants. For each quantity the list tabulates its description, symbol and value, and to the right, 
 as appropriate, its uncertainty in units that the quantity is given in. Further information is given at the end of this file. 
 

  Description of Quantity  Symbol = Value  Unit  Uncertainty 
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1  IAU 2009/2012 System of Astronomical Constants# 
 
1.1Natural Defining Constant:    
  Speed of light  c = 299792458  m/s  
 
1.2Auxiliary Defining Constants:    
  Astronomical unit (unit distance)##  au =A = 149597870700  m  
  1d(TT)/d(TCG)  L_G = 6.969290134D10   
  1d(TDB)/d(TCB)  L_B = 1.550519768D08   
  TDBTCB at T_0 = 2443144.5003725 (TCB)  TDB_0 = 6.55D05  s  
  Earth rotation angle (ERA) at J2000.0 UT1  theta_0 = 0.7790572732640  revolutions  
  Rate of advance of ERA  d(theta)/dUT1 = 1.00273781191135448  revs/UT1day  
 
1.3Natural Measurable Constant:    
  Constant of gravitation  G = 6.67428D11  m^3/kg/s^2  +/ 6.7D15 
 
1.4Other Constants:    
  Average value of 1d(TCG)/d(TCB)  L_C = 1.48082686741D08   +/ 2D17 
 
1.5Body Constants:    
  Solar mass parameter##  GMS = 1.32712442099D20  m^3/s^2 (TCB)  +/ 1D10 
   = 1.32712440041D20  m^3/s^2 (TDB)  +/ 1D10 
  Equatorial radius for Earth  a_E = a_e = 6378136.6  m (TT)  +/ 0.1 
  Dynamical formfactor for the Earth  J_2 = 0.0010826359   +/ 1D10 
  Longterm variation in J_2  \dot{J_2} = 3.0D09  per cy  +/ 6D10 
  Geocentric gravitational constant  GME = 3.986004418D14  m^3/s^2 (TCB)  +/ 8D05 
   = 3.986004415D14  m^3/s^2 (TT)  +/ 8D05 
   = 3.986004356D14  m^3/s^2 (TDB)  +/ 8D05 
  Potential of the geoid  W_0 = 6.26368560D07  m^2/s^2  +/ 0.5 
  Nominal mean angular vel.of Earth rotation omega = 7.292115D05  rad/s (TT)  
  Mass Ratio: Moon to Earth  M_M / M_E = 1.23000371D02   +/ 4D10 
 
  Ratio of the Mass of the Sun to the Mass of the Body*   
  Mass Ratio: Sun to Mercury###  M_S / M_Me = 6.0236D06   +/ 3D02 
  Mass Ratio: Sun to Venus  M_S / M_Ve = 4.08523719D05   +/ 8D03 
  Mass Ratio: Sun to Mars  M_S / M_Ma = 3.09870359D06   +/ 2D02 
  Mass Ratio: Sun to Jupiter  M_S / M_J = 1.047348644D03   +/ 1.7D05 
  Mass Ratio: Sun to Saturn  M_S / M_Sa = 3.4979018D03   +/ 1D04 
  Mass Ratio: Sun to Uranus###  M_S / M_U = 2.290298D04   +/ 3D02 
  Mass Ratio: Sun to Neptune  M_S / M_N = 1.941226D04   +/ 3D02 
  Mass Ratio: Sun to (134340) Pluto###  M_S / M_P = 1.36566D08   +/ 2.8D04 
  Mass Ratio: Sun to (136199) Eris  M_S / M_Eris = 1.191D08   +/ 1.4D06 
     
  *All values of the masses from Mars to Eris are the sum of the masses of the celestial bodies and its satellites. 
 
  Ratio of the Mass of the Body to the Mass of the Sun   
  Mass Ratio: (1) Ceres to Sun  M_Ceres /M_S = 4.72D10   +/ 3D12 
  Mass Ratio: (2) Pallas to Sun  M_Pallas /M_S = 1.03D10   +/ 3D12 
  Mass Ratio: (4) Vesta to Sun###  M_Vesta /M_S = 1.35D10   +/ 3D12 
 
1.6Initial Values at J2000.0:    
  Mean obliquity of the ecliptic, epsilon_0  epsilon_J2000.0 = 23 26 21.406  o ' "  
   = 84381.406  "  +/ 0.001 
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2 Constants from IAU WG on Cartographic Coordinates and Rotational Elements: 2009 
 
  Equatorial radii:    
  Mercury  = 2439.7  km  +/ 1.0 
  Venus  = 6051.8  km  +/ 1.0 
  Earth  = 6378.1366  km  +/ 0.0001 
  Mars  = 3396.19  km  +/ 0.1 
  Jupiter  = 71492  km  +/ 4 
  Saturn  = 60268  km  +/ 4 
  Uranus  = 25559  km  +/ 4 
  Neptune  = 24764  km  +/ 15 
  (134340) Pluto  = 1195  km  +/ 5 
  Moon (mean)  = 1737.4  km  +/ 1 
  Sun  = 696000  km  
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3 Other Constants 
 
  Lighttime for unit distance##  tau_A = A/c = 499.00478384  s  
   1/tau_A = 173.144632674  au/d  
     
  Mass Ratio: Earth to Moon  M_E/M_M = 1/mu = 81.300568   +/ 3D06 
  Mass Ratio: Sun to Earth  GMS/GME = 332946.0487   +/ 7D04 
  Mass of the Sun  M_S = S = GMS/G = 1.9884D30  kg  +/ 2D26 
  Mass of the Earth  M_E = E = GME/G = 5.9722D24  kg  +/ 6D20 
  Mass Ratio: Sun to Earth + Moon  (S/E)/(1 + mu) = 328900.5596   +/ 7D04 
     
  Earth, reciprocal of flattening IERS 2010  1/f = 298.25642   +/ 1D05 
     
  Rates of precession at J2000.0 (IAU 2006)    
  General precession in longitude  p_A = 5028.796195  "/Julian century (TDB)  
  Rate of change in obliquity  d(epsilon)/dT = 46.836769  "/Julian century (TDB)  
  Precession of the equator in longitude  d(psi)/dT = 5038.481507  "/Julian century (TDB)  
  Precession of the equator in obliquity  d(omega)/dT = 0.025754  "/Julian century (TDB)  
     
  Constant of nutation at epoch J2000.0  N = 9.2052331  "  
  Solar parallax, pi_odot  sin^1(a_e/A) = 8.794143  "  
  Constant of aberration at epoch J2000.0  kappa = 20.49551  "  
     
  Masses of the larger natural satellites:    
  Mass satellite/mass of the planet    
  Jupiter: Io  = 4.704D05   
  Europa  = 2.528D05   
  Ganymede  = 7.805D05   
  Callisto  = 5.667D05   
  Saturn: Titan  = 2.366D04   
  Uranus: Titania  = 4.06D05   
  Oberon  = 3.47D05   
  Neptune: Triton  = 2.089D04   
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 The IAU Working Group on Numerical Standards for Fundamental Astronomy maintains a website, http://maia.usno.navy.mil/NSFA, 
 which contains an agreed list of `Current Best Estimates' together with detailed information about the constants, and 
 relevant references. See footnotes below for more details. 
 
 This almanac, in certain circumstances, may not use constants from this list. The reasons and those constants used will be 
 given at the end of Section L Notes and References. 
 
 The units meter (m), kilogram (kg), and SI second (s) are the units of length, mass and time in the International System of 
 Units (SI). 
 
 The astronomical unit of time is a time interval of one day (D) of 86400 seconds. An interval of 36525 days is one Julian 
 century. Some constants that involve time, either directly or indirectly need to be compatible with the underlying 
 timescales. In order to specify this (TDB) or (TCB) or (TT), as appropriate, is included after the unit to indicate that the 
 value of the constant is compatible with the specified timescale, for example, TDBcompatible. 
 
 #The IAU 2009 System of Astronomical Constants classifies the constants into the groups shown. This may be redefined and 
 users should check the NSFA website for updates. 
 
 ##The astronomical unit of length (au) in metres is redefined as a conventional unit of length (resolution B2, IAU XXVIII GA 
 2012) in agreement with the value adopted by IAU 2009 Resolution B2; it is to be used with all time scales such as TCB, TDB, 
 TCG, TT, etc. Also the heliocentric gravitational constant GMS is renamed the solar mass parameter. Further details are 
 given in Section L Notes and References. 

 ###These values are those of the IAU 2009 System of Astronomical Constants. In May 2015 new best estimates were agreed (see 
 the NSFA website at http://maia.usno.navy.mil/NSFA/NSFA_cbe.html).  
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 2016 May 31 
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