The Universe is a big place... and it's getting bigger every day.
Our current model of the Universe, called the Big Bang Model,
is that the Universe originated approximately 13.7 billion
years ago and has been expanding ever since. It was always
assumed that expansion was slowing, with the gravity of the
Universe itself 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, the expansion ever accelerating.
Very little is known about this accelerated expansion, and less
is known about its cause. The SuperNova Acceleration Probe, or SNAP,
will fill the wide gaps in our knowledge. It will study exploding stars
called supernovae, as well as the gentle smearing of the light from
distant galaxies due to gravity —
called weak gravitational lensing — and put limits on what may or may
not be the force driving the outward pull on the Universe. 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.