Dirty Space and Supernovae (Forwarded)

News Office
Carnegie Institution of Washington
Washington, DC

Contact:
Andrew Steele, 202-478-8974

February 28, 2008

Dirty Space and Supernovae

Washington, DC -- Interstellar space may be strewn with tiny whiskers of
carbon, dimming the light of far-away objects. This discovery by scientists
at the Carnegie Institution may have implications for the "dark energy"
hypothesis, proposed a decade ago in part to explain the unexpected dimness
of certain stellar explosions called Type1a supernovae.

Type1a supernovae are among the brightest objects in the universe.
Astronomers use them as "standard candles" to gauge cosmological distances:
brighter-appearing supernovae are closer, dimmer ones are farther away. In
the late 1990s some astronomers noticed that some seemed too dim -- too far
away -- to be explained by conventional theories of the universe's
expansion. This led to the hypothesis that the expansion was accelerating,
pushed along by an unknown form of energy -- dark energy.

In the current study, published online February 28 in Science Express,
Andrew Steele and Marc Fries of the Carnegie Institution's Geophysical
Laboratory report the discovery of an unusual new form of carbon in minerals
within meteorites dating from the formation of the solar system. These
"graphite whiskers" were likely produced from carbon-rich gas at high
temperatures and were found within features called calcium-aluminum
inclusions, which at around 4.5 billion years old are the oldest known
solids in our solar system.

"During this time when the sun was young, the solar wind was very strong,"
says Fries. "So graphite whiskers formed near the sun could have been blown
into interstellar space. The same thing may have happened around other young
stars as well."

Graphite whiskers might also be produced and dispersed into space by
supernovae explosions.

A thin interstellar haze of graphite whiskers spewed from stars and
supernovae would affect how different wavelengths of light pass through
space. It has been postulated that wavelengths in the near infrared would be
particularly affected. It is the dimming of light from Type 1a supernovae at
these wavelengths that first led researchers to think that the universe's
expansion was accelerating and that therefore a hitherto unknown force "dark
energy"must exist. However, since the 1970s it has been postulated that
graphite or other whisker-like materials could explain the observations. The
presence of graphite whiskers in space has never been confirmed until this
study.

With the discovery of graphite whiskers in the meteorite, researchers can
test their properties against the cosmological models and astronomical
observations.

"If graphite whiskers in space are absorbing supernovae's light," says
Steele, "then this could affect measurements of the rate of the universe's
expansion. While we cannot comment further on the effects of whiskers on the
dark energy hypothesis it is important to study the characteristics of this
form of carbon carefully so we can understand its impact on dark energy
models. We'll then feed this data forward to the upcoming NASA and ESA
(European Space Agency) missions that will look for the effects of dark
energy."