The following table was taken from Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Preliminary Maps and Basic Results, C.L. Bennett et al. (2003), submitted to the Astrophysical Journal; available at http://lambda.gsfc.nasa.gov/
Description | Symbol | Value | + uncertainty | - uncertainty |
Total density |
![]() |
1.02 | 0.02 | 0.02 |
Equation of state of quintessence | w | < - 0.78 | 95% CL | -- |
Dark energy density |
![]() ![]() |
0.73 | 0.04 | 0.04 |
Baryon density |
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0.0224 | 0.0009 | 0.0009 |
Baryon density |
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0.044 | 0.004 | 0.004 |
Baryon density (cm-3) | nb | 2.5 × 10-7 | 0.1 × 10-7 | 0.1 × 10-7 |
Matter density |
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0.135 | 0.008 | 0.009 |
Matter density |
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0.27 | 0.04 | 0.04 |
Light neutrino density |
![]() ![]() |
< 0.0076 | 95% CL | -- |
CMB temperature (K) a | Tcmb | 2.725 | 0.002 | 0.002 |
CMB photon density (cm-3) b | n![]() |
410.4 | 0.9 | 0.9 |
Baryon-to-photon ratio |
![]() |
6.1 × 10-10 | 0.3 × 10-10 | 0.2 × 10-10 |
Baryon-to-matter ratio |
![]() ![]() |
0.17 | 0.01 | 0.01 |
Fluctuation amplitude in 8h-1 Mpc spheres |
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0.84 | 0.04 | 0.04 |
Low-z cluster abundance scaling |
![]() ![]() |
0.44 | 0.04 | 0.05 |
Power spectrum normalization (at k0 = 0.05 Mpc-1) c | A | 0.833 | 0.086 | 0.083 |
Scalar spectral index (at k0 = 0.05 Mpc-1) c | ns | 0.93 | 0.03 | 0.03 |
Running index slope (at k0 = 0.05 Mpc-1) c | dns / d lnk | -0.031 | 0.016 | 0.018 |
Tensor-to-scalar ratio (at k0 = 0.002 Mpc-1) | r | < 0.71 | 95% CL | -- |
Redshift of decoupling | zdec | 1089 | 1 | 1 |
Thickness of decoupling (FWHM) | ![]() |
195 | 2 | 2 |
Hubble constant | h | 0.71 | 0.04 | 0.03 |
Age of universe (Gyr) | t0 | 13.7 | 0.2 | 0.2 |
Age at decoupling (kyr) | tdec | 379 | 8 | 7 |
Age at reionization (Myr, 95% CL)) | tr | 180 | 220 | 80 |
Decoupling time interval (kyr) | ![]() |
118 | 3 | 2 |
Redshift of matter-energy equality | zeq | 3233 | 194 | 210 |
Reionization optical depth | ![]() |
0.17 | 0.04 | 0.04 |
Redshift of reionization (95% CL) | zr | 20 | 10 | 9 |
Sound horizon at decoupling (°) |
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0.598 | 0.002 | 0.002 |
Angular diameter distance to decoupling (Gpc) | dA | 14.0 | 0.2 | 0.3 |
Acoustic scale d |
![]() |
301 | 1 | 1 |
Sound horizon at decoupling (Mpc) d | rs | 147 | 2 | 2 |
a from COBE (Mather et al., 1999) | ||||
b derived from COBE (Mather et al., 1999) | ||||
c
leff ![]() |
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d
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