Some Useful Constants for Astronomy
| Physical Constants |
| Name |
Value |
| speed of light (c) |
2.9979 × 108 m/s |
| gravitational constant (G) |
6.674 × 10−11 m3/(kg s2) |
| Planck’s constant (h) |
6.626 × 10−34 J-s |
| mass of a hydrogen atom (MH) |
1.673 × 10−27 kg |
| mass of an electron (Me) |
9.109 × 10−31 kg |
| Rydberg constant ( [latex]{R}_{\infty }[/latex] ) |
1.0974 × 107 m−1
|
| Stefan-Boltzmann constant (σ) |
5.670 × 10−8 J/(s·m2 deg4)1
|
| Wien’s law constant (λmaxT) |
2.898 × 10−3 m K |
| electron volt (energy) (eV) |
1.602 × 10−19 J |
| energy equivalent of 1 ton TNT |
4.2 × 109 J |
| Astronomical Constants |
| Name |
Value |
| astronomical unit (AU) |
1.496 × 1011 m |
| Light-year (ly) |
9.461 × 1015 m |
| parsec (pc) |
3.086 × 1016 m = 3.262 light-years |
| sidereal year (y) |
3.156 × 107 s |
| mass of Earth (MEarth) |
5.974 × 1024 kg |
| equatorial radius of Earth (REarth) |
6.378 × 106 m |
| obliquity of ecliptic |
23.4° 26’ |
| surface gravity of Earth (g) |
9.807 m/s2
|
| escape velocity of Earth (vEarth) |
1.119 × 104 m/s |
| mass of Sun (MSun) |
1.989 × 1030 kg |
| equatorial radius of Sun (RSun) |
6.960 × 108 m |
| luminosity of Sun (LSun) |
3.85 × 1026 W |
| solar constant (flux of energy received at Earth) (S) |
1.368 × 103 W/m2
|
| Hubble constant (H0) |
approximately 20 km/s per million light-years, or approximately 70 km/s per megaparsec |
Footnotes
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1 deg stands for degrees Celsius or kelvins