To be published in "Supernovae & Gamma Ray Bursts",
K. Weiler, Ed., Springer, Lecture Notes in Physics.
For a PDF version of the article, click
here.
astro-ph/0303428.
For a Postscript version of the article, click
here.
Abstract. Over the past decade, supernovae have emerged as some
of the most
powerful tools for measuring extragalactic distances. A well developed
physical understanding of type II supernovae allow them to be used to
measure distances independent of the extragalactic distance scale. Type
Ia supernovae are empirical tools whose precision and intrinsic
brightness make them sensitive probes of the cosmological
expansion. Both types of supernovae are consistent with a Hubble
Constant within ~ 10% of H0 = 70 km s-1
Mpc-1. Two teams have used
type Ia supernovae to trace the expansion of the Universe to a
look-back time more than 60% of the age of the Universe. These
observations show an accelerating Universe which is currently best
explained by a cosmological constant or other form of dark energy with
an equation of state near w = p /
= - 1. While
there are many possible remaining systematic effects, none appears large
enough to challenge these current results. Future experiments are planned to
better characterize the equation of state of the dark energy leading to
the observed acceleration by observing hundreds or even thousands of
objects. These experiments will need to carefully control systematic
errors to ensure future conclusions are not dominated by effects
unrelated to cosmology.
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