Washington, Feb 29 : Scientists at the Carnegie Institution, US, have discovered that interstellar space may be strewn with tiny whiskers of carbon, dimming the light of far-away objects, which may have implications for the "dark energy" hypothesis.
The "dark energy" hypothesis was 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 new study by the Carnegie Institution, the discovery of an unusual new form of carbon in minerals within meteorites has been reported, which dates from the formation of the solar system.
According to the study, 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," said Marc Fries from the Carnegie Institution's Geophysical Laboratory. "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," he added.
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.
"If graphite whiskers in space are absorbing supernovae's light, then this could affect measurements of the rate of the universe's expansion," said Andrew Steele, a part of the research team.