Article Posted on : - Oct 05, 2012

WASHINGTON (PTI): NASA has made the most precise measurement yet of the Hubble constant, the rate at which our universe is expanding.

The Hubble constant is named after the astronomer Edwin P Hubble, who astonished the world in the 1920s by confirming our universe has been expanding since it exploded into being 13.7 billion years ago.

In the late 1990s, astronomers discovered the expansion is accelerating, or speeding up over time. Determining the expansion rate is critical for understanding the age and size of the universe, NASA said.

NASA's Spitzer Telescope took advantage of long-wavelength infrared light to make its new measurement.

It improves by a factor of 3 on a similar, seminal study from the Hubble telescope and brings the uncertainty down to 3 per cent, a giant leap in accuracy for cosmological measurements.

The newly refined value for the Hubble constant is 74.3 + 2.1 kilometers per second per megaparsec.

A megaparsec is roughly 3 million light-years.

"Spitzer is yet again doing science beyond what it was designed to do," said project scientist Michael Werner at NASA's Jet Propulsion Laboratory in Pasadena, California.

Werner has worked on the mission since its early concept phase more than 30 years ago.

"First, Spitzer surprised us with its pioneering ability to study exoplanet atmospheres," said Werner, "and now, in the mission's later years, it has become a valuable cosmology tool," said Werner.

Dark energy is thought to be winning a battle against gravity, pulling the fabric of the universe apart, researchers said in a statement.

"This is a huge puzzle," said study lead author Wendy Freedman of the Observatories of the Carnegie Institution for Science in Pasadena.

"It's exciting that we were able to use Spitzer to tackle fundamental problems in cosmology: the precise rate at which the universe is expanding at the current time, as well as measuring the amount of dark energy in the universe from another angle," he said.

Freedman led the ground-breaking Hubble Space Telescope study that earlier had measured the Hubble constant.