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A Python package that provides astronomical constants.


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A Python package that provides astronomical constants. The code is being developed by Marc van der Sluys of the department of Astrophysics at the Radboud University Nijmegen, the Institute of Nuclear and High-Energy Physics (Nikhef), and the Institute for Gravitational and Subatomic Physics (GRASP) at Utrecht University, all in The Netherlands. The AstroConst package can be used under the conditions of the EUPL 1.2 licence.

Note that the package is currently is its alpha stage, and things may still change as I start using this.


This package can be installed using pip install astroconst. This should automatically install the dependency package numpy, if it has't been installed already. If you are installing by hand, ensure that this package is installed as well.

Example use

SI units should be used everywhere - no ergs, dyn or cm (sorry!). Values include mathematical constants (like π), angle-conversion factors (from/to radians, degrees, hours, arcseconds, ...), calendar stuff (names of weekdays and months, JDs, lengths of days, months and years), solar-system objects (Sun, Moon, planet names diameters, orbital separations, etc. - note that Moon = planet #0), and some basic physical constants ((Stefan-)Bolzmann, Planck, speed of light, etc.).

The submodule aa contains constants published by the Astronomical Almanac, converted to Python.

"""Example Python script using the AstroConst package."""

import astroconst as ac

print(ac.c)     # 299792458 (speed of light, quick access)
print(ac.aa.c)  # Access constants from Astronomical Almanac

print(ac.jd2000)  # 2451545
print(ac.m_sun)  # 1.9891e+30 (kg)
print(ac.sol_const)  # 1361.5 (W/m2)

print(ac.year_jul)  # 31557600.0 (s)
print(ac.year_jul/  # 365.25 (days)
print(ac.month_syn/  # 29.530588853 (days)

print('The diameter of '+ac.plname_en[5]+' is '+str(ac.pl_d[5]/' km')
# The diameter of Jupiter is 142984 km

print('a_'+ac.plname_en[0]+' = '+str(ac.pl_a[0]/' km')
# a_Moon = 384400.0 km (Moon = planet #0)

print(ac.dow_en_abr[0])  # Sun
print(ac.months_en[3])  # March

AstroConst pages

Author and licence


Copyright (c) 2022 Marc van der Sluys


A Python package that provides astronomical constants.