Apart from the Planck satellite, the Wilkinson Microwave Anisotropy Probe (WMAP) was instrumental in establishing an accurate age of the universe, though other measurements must be folded in to gain an accurate number. CMB measurements are very good at constraining the matter content Ω Ω m , and curvature parameter Ω Ω k . It is not as sensitive to Ω Ω Λ Λ directly, partly because the cosmological constant becomes important only at low redshift. The most accurate determinations of the Hubble parameter H 0 are currently believed to come from measured brightnesses and redshifts of distant Type Ia supernovae. Combining these measurements leads to the generally accepted value for the age of the universe quoted above.