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The Universe is expanding faster than expected, providing that astronomers may have some new physics in their theories of how the cosmos works, a new study reports.
The revised expansion rate is about 10% faster than that predicted by the observations of the universe big Bang, according to the new research. The study also significantly reduces the probability that this disparity is coincidental, from 1 in 3,000 to just 1 in 100,000.
Adam Riess, lead research author of physics and astronomy at The Johns Hopkins University in Baltimore, said in a statement.
"This is not what we expected," said Riess, who won the Nobel Prize for Physics in 2011 (along with Brian Schmidt and Saul Perlmutter) for showing, in the late 1990s, that the universe's expansion is accelerating. It's unclear what's driving this surprising acceleration, but many astronomers invoke a mysterious, repulsive force called dark energy.
Related: The Universe: Big Bang to Now in 10 Easy Steps
This illustration shows the three basic steps astronomers use to calculate how fast the universe expands over time, a value called the constant Hubble. All the steps involve building a strong "cosmic distance ladder," by starting with measuring accurate distances to nearby galaxies and then moving to galaxies farther and farther away. This ladder is a series of measurements of different types of astronomical objects with an intrinsic brightness that researchers can use to calculate distances.
(Image: NASA, ESA, and A. Feild (STScI))
In the new study, Riess and his colleagues used Hubble Space Telescope to study 70 Cepheid variable stars in the Large Magellanic Cloud (LMC), one of the Milky Way's satellite galaxies. Cepheid variables and predictable rates and are therefore "standard candles" that allow astronomers to calculate distances.
Superschrift, superschrift, ausschrift, auspices, für kommunikation, für kommittenschrift, Riess, Schmidt and Perlmutter's Studies of Type 1a supernovae led to their Nobel-winning discovery.
Riess and his team also made observations made by the Araucaria Project, a collaboration involving researchers in the United States, Europe and Chile, who studied various LMC binary star systems, noting the dimming that occurred when one star passed in front of its neighbor. This work provides additional distance measurements, helping the study team to improve their understanding of Cepheids' intrinsic brightness.
The researchers used all of this information to calculate the universe's present-day expansion rate, a value known as the Hubble constant, after American astronomer Edwin Hubble. The new number is about 46.0 miles (74.03 kilometers) per second per megaparsec; one megaparsec is roughly 3.26 million light-years.
The uncertainty is just 1.9%, the researchers said. That 's the lowest added value of this approach – down from 10% in 2001 and 5% in 2009.
The "expected" expansion rate, by contrast, is about 41.9 miles (67.4 km) per second per megaparsec. This projection rate is based on observations that Europe's Planck satellite made of the cosmic microwave background – the light left over the Big Bang that created the universe 13.82 billion years ago.
"This is not just two experiments disagreeing." We are measuring something fundamentally different, "Riess said.
"One is a measurement of how fast the world 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 should be expanding," he added. "If these values do not agree, it becomes a likelihood that we are missing something in the cosmological model that connects the two eras."
The new study was published today (April 25) in The Astrophysical Journal. You can read it for free at the online preprint site arXiv.org.
Mike Wall's book on the search for alien life, "Out There"(Grand Central Publishing, 2018; Karl Tate), is out now. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom gold Facebook.
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