New Hubble measures confirm the universe is growing faster than expected

New measurements from NASA's Hubble Space Telescope confirm that the Universe is growing about 9% faster than expected, according to its trajectory observed shortly after the big bang, according to astronomers.

The new measures, published on 25 April in the Letters from the Astrophysical Journalreduce the chance that the disparity is an accident of 1 in 3,000 to only 1 in 100,000 and suggest that new physics may be needed to better understand the cosmos.

"This mismatch has grown and reached a point that is really impossible to consider as a stroke of luck.This is not what we expected," says Adam Riess , Distinguished Professor of Physics and Astronomy at Johns Hopkins University of Bloomberg. the project manager.

In this study, Riess and his team SH0ES (Supernovae, H0, for the state equation) analyzed the light of 70 stars of our neighboring galaxy, the Great Magellanic Cloud, with a new method allowing to quickly capture images of these stars. The stars, called cepheid variables, illuminate and darken at a predictable rate used to measure nearby intergalactic distances.

The usual method of measuring stars takes a lot of time; Hubble can observe only one star for every 90-minute orbit around the Earth. Using their new method called DASH (Drift And Shift), researchers use Hubble as a "viewfinder" camera to watch groups of Cepheids, allowing the team to observe a dozen Cepheids in the same lapse of time normally take to observe a single.

With this new data, Riess and his team were able to strengthen the basics of the cosmic distance scale, used to determine distances in the universe, and to calculate the Hubble constant, a value of the speed at which the cosmos expands in time.

The team combined its Hubble measurements with another set of observations made by the Araucaria project, a collaboration between astronomers from institutions in Chile, the United States and Europe. This group made distance measurements up to the great magellanic cloud by observing the decrease in light as a star passes in front of its partner, which eclipses binary star systems.

The combined measurements allowed the SH0ES team to refine the true brightness of the Cepheids. With this more accurate result, the team could then "tighten bolts" from the rest of the distance scale that uses explosive stars called supernovae to extend deeper into space.

As the team's measurements became more accurate, their calculation of Hubble's constant remained at odds with the expected value of observations of the expansion of the first universe by the Planck satellite of the European Space Agency based on the conditions observed by Planck 380 000 years after the Big Bang.

"It's not just two experiences that disagree," said Riess. "We measure something fundamentally different, one is a measure of the speed at which the universe is developing today, as we see it.The other is a prediction based on the physics of the first universe and measures of the speed at which it should develop If these values ​​do not match, it becomes very likely that we are missing something in the cosmological model that connects the two epochs. "

Although Riess does not know exactly why the difference exists, he and the SH0ES team will continue to tweak the Hubble constant to reduce uncertainty to 1%. These latest measures have reduced the uncertainty of the rate of expansion from 10% in 2001 to 5% in 2009 and 1.9% in this study.