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Illustration shows the three steps astronomers used to measure the universe's expansion rate to an unprecedented accuracy. (Credit: NASA, ESA, A. Feild (STScI), and A. Riess (STScI/JHU))
Illustration shows the three steps astronomers used to measure the universe’s expansion rate to an unprecedented accuracy. (Credit: NASA, ESA, A. Feild (STScI), and A. Riess (STScI/JHU))

New research from NASA’s Hubble Space Telescope team suggests that the universe is expanding significantly faster than astronomers originally thought. The latest measurements indicate an expansion rate five to nine percent faster than expected.

Nobel Laureate Adam Riess, who led the study, began searching for a more accurate calculation of the universe’s expansion rate in 2005.

NASA’s astronomers compared the observed brightness of about 2,400 Cepheid stars and 300 Type la supernovae. They then compared those distances with the expansion of space, measured by light from receding galaxies. They measured the new expansion rate with unprecedented accuracy, reducing uncertainty to just 2.4 percent, according to NASA.

The new calibration doesn’t match the original expansion rate that astronomers predicted from the outset of the Big Bang,

“If we know the initial amounts of stuff in the universe, such as dark energy and dark matter, and we have the physics correct, then you can go from a measurement at the time shortly after the big bang and use that understanding to predict how fast the universe should be expanding today,” Riess said in a NASA press release. “However, if this discrepancy holds up, it appears we may not have the right understanding, and it changes how big the Hubble constant should be today.”

It’s unclear why the universe is expanding so much faster than expected. NASA says it may be caused by dark energy pushing galaxies apart with greater or growing force. Another theory suggests that the invisible matter that comprises most of the galaxy (a.k.a. dark matter) has unknown properties. The space agency also hypothesizes that a subatomic particle known as “dark radiation” may be responsible. A fourth troubling possibility: Einstein’s theory of gravity is incomplete.

Astronomers continue to use the Hubble Telescope to observe the universe’s expansion rate, aiming to reduce uncertainty to 1 percent.

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