Science

Universe’s Expansion Might Be Occurring Faster Than Previously Thought

Universe's Expansion
Image Credit: NASA, ESA, A. Riess (STScI/JHU) and Palomar Digitized Sky Survey

NASA researchers believe the universe is expanding more quickly than previous estimates. According to a new study published in The Astrophysical Journal, scientists have recalculated estimates for the the universe’s expansion rate.

When the researchers revised their estimate for the universe’s expansion rate, the newly-calculated rate was 10% faster than the previously-predicted trajectory following the so-called “Big Bang.”

“This mismatch has been growing and has now reached a point that is really impossible to dismiss as a fluke,” lead author and Johns Hopkins professor Adam Riess said in a statement.

Researchers used the Hubble Space Telescope to study 70 Cepheid variable stars in the Large Magellanic Cloud (LMC), which is considered to be one of the Milky Way’s satellite galaxies. They dim and brighten at predictive rates, allowing scientists to easily calculate distances.

The team also used observations captured by the Araucaria Project, which involves researchers in the United States, Europe and Chile. Researchers participating in the project measured distances to the LMC by studying the the dimming which occurs when one star passes in front of a neighbor star. Researchers used this method to better understand the Cepheids’ intrinsic brightness.

Using these methods, researchers said they estimated the universe’s expansion rate as of today, a value which is called the Hubble constant, after American astronomer Edwin Hubble. They calculated the new number at 46 miles per second per megaparsec (3.26 million light years are contained within one megaparsec). Researchers also attributed an uncertainty rate of 1.9% to this number, which is the lowest uncertainty value that has ever been estimated using the previously-described method. It surpassed the previous numbers of 10% in 2001 and 5% in 2009.

The expansion rate researchers expected was 41.9 miles per second per megaparsec, although the rate was based on the observations captured by Europe’s Planck satellite.

“This is not just two experiments disagreeing. We are measuring something fundamentally different,” Riess said. “One is a measurement of how fast the universe is expanding today, as we see it. The other is a prediction based on the physics of the early universe and on measurements of how fast it ought to be expanding. If these values don’t agree, there becomes a very strong likelihood that we’re missing something in the cosmological model that connects the two eras.”

The study is currently available free on the preprint website arXiv.org.