The Universe is a big place... and it's getting bigger every day.
The Universe originated approximately 13.7 billion
years ago as a hot, nearly uniform gas, and has been expanding ever since. It was always
assumed that expansion was slowing, with the tug of gravity
applying the brakes. But shortly before the
end of the 20th century astronomers got a big surprise: the Universe
was not slowing down, it was speeding up. We live in an accelerating Universe.
Very little is known about this accelerated expansion, and even less
about its cause. The SuperNova Acceleration Probe, or SNAP,
is designed to shed light on this mystery. SNAP will use precise measurements of exploding stars
called supernovae, as well as the subtle distortion of the light from
distant galaxies, to measure the expansion history of the Universe.
The details of this history may reveal the origin of the cosmic acceleration. SNAP will
investigate over one thousand square degrees of sky — more than
5000 times the size of the full Moon! — with a 500 megapixel camera.
SNAP is being proposed for the Joint Dark Energy Mission
(JDEM), which is a cooperative venture between
U.S. Department of Energy.
SNAP could be ready to launch by 2013.