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. 1999 Apr 13;96(8):4224-7.
doi: 10.1073/pnas.96.8.4224.

Supernovae, an accelerating universe and the cosmological constant

R P Kirshner  1
Affiliations

Supernovae, an accelerating universe and the cosmological constant

R P Kirshner. Proc Natl Acad Sci U S A. .

Abstract

Observations of supernova explosions halfway back to the Big Bang give plausible evidence that the expansion of the universe has been accelerating since that epoch, approximately 8 billion years ago and suggest that energy associated with the vacuum itself may be responsible for the acceleration.

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Figures

Figure 1
Figure 1
SN 1994D, a nearby supernova imaged with the Hubble Space Telescope.
Figure 2
Figure 2
High redshift supernovae observed with the Hubble Space Telescope.
Figure 3
Figure 3
The Hubble diagram for SN Ia. The lines show the predictions for cosmologies with varying amounts of Ωm and ΩΛ. The observed points all lie above the line for a universe with zero Λ. The lower panel, with the slope caused by the inverse square law taken out, shows the difference between the predictions more clearly and shows why a model with ΩΛ > 0 is favored.
Figure 4
Figure 4
The Ωm, ΩΛ plane. Using the supernova data, a likelihood analysis shows the probability that any chosen pair of Ωm, ΩΛ values fits the observations. The allowed region is large and follows the direction of Ωm − ΩΛ = a constant. Ωm = 1 is far from the allowed region. Many pairs of geometrically flat solutions with Ωm + ΩΛ = 1 are possible. ΩΛ = 0 is not very probable in this analysis.
Figure 5
Figure 5
Ωm, ΩΛ plane for the combination of supernova constraints and measurements of the CMB.
See this image and copyright information in PMC

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