(Barred spiral galaxy, Eridanus constellation)
The following table contains the values of the constants and parameters commonly used in astrophysics and also more particularly in cosmology. Concerning the cosmological parameters, the ΛCDM model which is the basis of the standard model of the cosmology is used and the numerical values correspond to the best fit within a confidence interval of 68% (except explicit mention).
These values are gathered in the annual review of the Particle Data Group.
| Quantity | Symbol, equation | Value |
|---|---|---|
| Speed of light in a vacuum | c | 299 792 458 m·s-1 |
| Newtonian constant of gravitation | GN | 6,673 84(80)×10-11 m3·kg-1·s-2 |
| Astronomical unit (constant) | ua | 149 597 870 700 m |
| Tropical year (from equinox to equinox) | year | 149 597 870 700 m |
| Sidereal year (from fixed star to fixed star) | 31 558 149,8 s | |
| Average sidereal day | 23 h 56 min 04,090 53 s | |
| Jansky | Jy | 1×10-26 W·m-2·Hz-1 |
| Planck mass | √(ℏc/GN) | 12,209 0(9)×1018 GeV/c2 = 21,764 5(16)×10-9 kg |
| Planck length | √(ℏGN/c3) | 1,616 24(12)×10-35 m |
| Planck time | √(ℏGN/c5) | 5,39121×10-44 s |
| Planck temperature | TP = √(ℏc5/GNk2) | 1,41679×1032 K |
| Current Hubble constant | H0 | 100 h·km·s-1·Mpc-1 = h × (9,77813 Ga)−1 |
| Standardized Hubble constant | h | 0,73+0,04−0,03 |
| Hubble length | c/H0 | ≈ 120×1021 km |
| Parsec (1 UA / 1 arc sec) | pc | 30,856775814672×1012 km = 3,26… al |
| Light-year | yl | 0,306 6…pc = 9,461…×1012 km |
| Schwarzschild radius of the Sun | 2GNMS/c2 | 2,95325008 km |
| Sun mass | MS | 1,988 44(30)×1030 kg |
| Equatorial radius of the Sun | RS | 696 100 km |
| Brightness of the Sun | LS | 384,6±0,8×1024 W |
| Schwarzschild radius of Earth | 2GNME/c2 | 8,87005622 mm |
| Earth mass | ME | 5,972 3(9)×1024 kg |
| Earth’s average equatorial radius | RE | 6,378140×106 m |
| Speed of the Sun around the center of the Milky Way | Θo | 220(20) km·s-1 |
| Distance from the Sun to the galactic center | Ro | 8,0(5) kpc |
| Local density of the galactic disc | ρdisc | 3-12×10-24 g·cm-3 ~ 2-7 GeV/c2·cm-3 |
| Local density of the galactic halo | ρhalo | 2-13×10-25 g·cm-3 ~ 0,1-0,7 GeV/c2·cm-3 |
| Current CMB Temperature | T0 | 2,725±0,001 K |
| Current CMB dipole range | 3,346±0,017 mK | |
| Speed of the Sun in relation to the CMB | 369±2 km·s-1 in the direction of (l,b) = (263,86°±0,04°, 48,24°±0,010°) | |
| Speed of the local group compared to the CMB | vLG | 627±22 km·s-1 in the direction of (l,b) = (276°±3°, 30°±3°) |
| Boltzmann constant (or entropy density) | s/k | 2 889,2 (T/2,725)3·cm-3 |
| CMB photon density | nγ | 410,5±0,5 cm-3 |
| Scaling factor for the cosmological constant | c2/3H02 | 2,853×1051 h-2·m2 |
| Critical mass density of the Universe | ρc = 3H02/8πGN | 2,77536627×1011 h2·MS·Mpc-3 = 1,878 37(28)×10-29 h2·g·cm-3 = 1,053 69(16)×10-5 h2·(GeV/c2)·cm-3 |
| Density of matter without pressure in the universe | Ωm = ρm/ρc | 0,127+0,007−0,009h-2 ⇒ 0,24+0,03−0,04 |
| Density of baryons in the universe | Ωb = ρb/ρc | 0,0223+0,0007−0,0009h-2 ⇒ 0,042+0,003−0,005 |
| Density of dark matter in the universe | Ωdm = Ωm − Ωb | 0,105+0,007−0,010h-2 ⇒ 0,20+0,02−0,04 |
| Density of radiation in the universe | Ωγ = ργ/ρc | (2,471±0,004)h×10-5 h-2 ⇒ (4,6±0,5)×10-5 |
| Density of neutrinos in the universe | Ων | < 0,007 h-2 ⇒ < 0,014 (at a confidence level of 95%) |
| Dark energy density in the universe | ΩΛ | 0,76+0,04−0,06 |
| Total energy density in the universe | Ωtot = Ωm + Ωγ + Ων + ΩΛ | 1,003+0,013−0,017 |
| Baryons/photons ratio | η = nb/nγ | 4,7×10-10 < η < 6,5×10-10 (95 %) |
| Density of number of baryons | nb | 1,9×10-7 cm-3 < nb < 2,7×10-7 cm-3 |
| Parameter of equation of state for dark energy | w | -0,97+0,07−0,09 |
| Amplitude fluctuation at scale 8: h−1·Mpc | σ8 | 0,74+0,05−0,06 |
| Scalar spectral index of the adjustment of the power law to the observations | ns | 0,951+0,015−0,019 |
| Variation of the spectral index for k0 = 0,05 Mpc-1 | dns/d ln k | -0,055+0,029−0,035 |
| Relationship of tensor/scalar perturbations in the CMB for k0 = 0,05 Mpc-1 | r = T/S | < 0,55 (95 %) |
| Optical reionization depth | τ | 0,09±0,03 |
| Age of the universe | t0 | 13,7+0,1−0,2 Gy |
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