Astronomical Constants

Constant

Value

Astronomical unit (au)	149,597,870 km
Speed of light in a vacuum (c)	299,792.458 km/sec
Solar parallax	8.794148 arc seconds
Mass of the sun	1.9891 × 1030 kg
Mass of the earth	5.9742 × 1024 kg
Mass of the moon	7.3483 × 1022 kg
Light-year (ly)	9.4605 × 1012 km = 0.30660 pc
Parsec (pc)	30.857 × 1012 km = 3.26161 ly
Obliquity of the eliptic (2000)	23 ° 26 ' 21.448 '
General precession (2000)	50.290966 arc seconds/year
Constant of nutation (2000)	9.2025 arc seconds
Constant of aberration (2000)	20.49552 arc seconds