Mass of the observable universe
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The mass of the observable universe can be estimated using estimations for its density and size. Estimates of its density are obtained by studying fluctuations in cosmic microwave background radiation, superclusters, and Big Bang nucleosynthesis. These yield a density estimate of 
. Estimates of the size of the observable universe vary, but a size estimate of 
light years yields a mass estimate of 
.[1]
Another way to calculate the mass of the observable universe is to assume a mean solar mass and to multiply that by an estimate of the number of stars in the observable universe. The estimate of the number of stars in the universe is in turn derived from the volume of the observable universe (
) and a stellar density calculated from observations by the Hubble Space Telescope (
) yielding an estimate of the number of stars in the observable universe of 
. Assuming the mass of Sol (
) as the mean solar mass (on the basis that the large population of dwarf stars balances out the population of stars whose mass is greater than Sol) and rounding the estimate of the number of stars up to 1022stars yields a mass of the observable universe as 
.[2]
Hoyle calculates the mass of an observable steady-state universe using the formula 4 / 3πρ(c / H)3, or c3 / 2GH.[3]
[edit] References
- ^ Jagadheep D. Pandian (June 2002). What is the mass of the Universe?. Curious About Astronomy.
- ^ . "On the expansion of the universe" (PDF). NASA Glenn Research Centre.
- ^ Helge Kragh (1999-02-22). Cosmology and Controversy: The Historical Development of Two Theories of the Universe. Princeton University Press, 212. ISBN 0-691-00546-X.
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