Hubble Space Telescope: History and Discoveries
that Changed Our View of the Universe   or   index.html

  By determining the rate at which the universe is expanding,
  Hubble may have helped solve the mystery of how old the
  universe is, but it unexpectedly turned up an even more
  profound one -- the fact that the rate of the universe's
  expansion is not slowing down or even constant, but is
  inexplicably accelerating. The culprit behind this, dubbed
  dark energy, is now thought to make up about 70 percent of
  the combined mass-energy in the entire universe, and it
  remains an utter enigma. Solving this mystery could
  revolutionize physics as we know it.

Science Friday | Exploring An Ever-Expanding Universe (30 min)

The Nobel Prize in Physics 2011

  The Nobel Prize in Physics 2011 was divided, one half
  awarded to Saul Perlmutter, the other half jointly to Brian
  P. Schmidt and Adam G. Riess "for the discovery of the
  accelerating expansion of the Universe through observations
  of distant supernovae".

Press Release | Written in the stars

  What will be the final destiny of the Universe? Probably it
  will end in ice, if we are to believe this year's Nobel
  Laureates in Physics. They have studied several dozen
  exploding stars, called supernovae, and discovered that the
  Universe is expanding at an ever-accelerating rate. The
  discovery came as a complete surprise even to the Laureates

  In 1998, cosmology was shaken at its foundations as two
  research teams presented their findings. Headed by Saul
  Perlmutter, one of the teams had set to work in 1988. Brian
  Schmidt headed another team, launched at the end of 1994,
  where Adam Riess was to play a crucial role.

  The research teams raced to map the Universe by locating the
  most distant supernovae. More sophisticated telescopes on
  the ground and in space, as well as more powerful computers
  and new digital imaging sensors (CCD, Nobel Prize in Physics
  in 2009), opened the possibility in the 1990s to add more
  pieces to the cosmological puzzle.

  The teams used a particular kind of supernova, called type
  Ia supernova. It is an explosion of an old compact star that
  is as heavy as the Sun but as small as the Earth. A single
  such supernova can emit as much light as a whole galaxy. All
  in all, the two research teams found over 50 distant
  supernovae whose light was weaker than expected - this was a
  sign that the expansion of the Universe was accelerating.
  The potential pitfalls had been numerous, and the scientists
  found reassurance in the fact that both groups had reached
  the same astonishing conclusion.

  For almost a century, the Universe has been known to be
  expanding as a consequence of the Big Bang about 14 billion
  years ago. However, the discovery that this expansion is
  accelerating is astounding. If the expansion will continue
  to speed up the Universe will end in ice.

  The acceleration is thought to be driven by dark energy, but
  what that dark energy is remains an enigma - perhaps the
  greatest in physics today. What is known is that dark energy
  constitutes about three quarters of the Universe. Therefore
  the findings of the 2011 Nobel Laureates in Physics have
  helped to unveil a Universe that to a large extent is
  unknown to science. And everything is possible again.

Why the Runaway Universe Discovery Won the Nobel Prize in
Physics (4+ min)

Why the universe probably is "flat" (15 min)

  Lawrence Krauss makes the case for a flat universe, where
  the total amount of mass-energy in the universe is and
  always has been zero.


A Universe From Nothing' by Lawrence Krauss, AAI 2009 (1+ hr)


Dark Energy

  In physical cosmology and astronomy, dark energy is a
  hypothetical form of energy which permeates all of space and
  tends to accelerate the expansion of the universe. Dark
  energy is the most accepted hypothesis to explain the
  observations since the 1990s indicating that the universe is
  expanding at an accelerating rate.

NASA's Hubble rules out one alternative to dark energy

  Astronomers using NASA's Hubble Space Telescope have ruled
  out an alternate theory on the nature of dark energy after
  recalculating the expansion rate of the universe to
  unprecedented accuracy.

Hubble Confirms Dark Energy's Clout

  By the way, this work was made possible by a little-known
  but astounding effort undertaken with the Hubble Space
  Telescope called the Cosmic Evolution Survey, or COSMOS.
  From October 2003 to November 2005, HST's Advanced Camera
  for Surveys acquired 38-minute-long exposures of 575
  overlapping fields, collectively covering a patch of Sextans
  a full 1.3 square.

  COSMOS took 1,000 hours of Hubble time to acquire -- making
  it even more ambitious than observatory's famous, but much
  narrower, "deep fields." At full resolution, the final image
  is 100,800 pixels on a side -- imagine a page in Sky &
  Telescope 28 feet on a side and you'll get the picture (so
  to speak).

Astronomy Picture of the Day Archive