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constants - list of useful constants


Here we tabulate some convenience values we often use in astronomy. Only a few are available in programs that use nemoinp(1NEMO)


3.1415926    pi, math [nemoinp: pi]
2.7182818    e, math
57.295780    Degrees per radian (180/pi)
206264.81    Arcseconds per Radian (3600*180/pi)
2.35482        STOF = 2*sqrt(2*ln(2)) - the FWHM/sigma of a gaussian 
2.50663        sqrt(2*pi) - flux (gauss1d) = sqrt(2*pi)  * peak * sigma
1.13309        BOF (beam oversampling factor) = 1.13309 * (FWHM/PIXEL)^2  = pi/(4*ln(2))
1.4826        rms = 1.4826*MAD (Median Absolution Deviation)
3.26163        pc/ly 
6.6743e-11    G, grav constant in MKS units [nemoinp: G]
299792.458    c, speed of light, in km/s [nemoinp: c]
3.155693e7    yr, seconds in a year (or 32 Ms)
149597870.700    AU, in km, as per IAU 2009 resolution B2 (or 150 Gm = giga-meter)
3.08567758e13    pc, defined as 648000/pi*AU, as per IAU 2015 resolution B2,
in km (=30 Peta-meters)
1.989e30    Solar Mass, in kg (or 2000 Qg = quetta-gram)
5.974e24    Earth Mass, in kg (or 6 Rg = ronna-gram)
6378.1        Earth Radius, in km
1420.405751786    HI spectral line, in MHz
115.2712018    CO(1-0) spectral line, in GHZ
29.786        average earth orbital speed around sun, km/s
0.4638        earth rotation speed at equator, km/s


Galactic constants such as distance to the galactic center (8.5 kpc) or orbital speed of LSR (220 km/s) , are still subject to change. See also mkgalorbit(1NEMO) .

See Also

ccdstat(1NEMO) , ccdsmooth(1NEMO) , mkgalorbit(1NEMO) , units(1NEMO) , units(5NEMO) , data(5NEMO)


Peter Teuben


inc/cgs.h    constants in CGS units
inc/mks.h    constants in MKS units
inc/stdinc.h    PI
data         NEMO standard repository area for data files.

Update History

21-aug-2020    created      PJT

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