Dark energy, a mysterious invisible force believed to play a role in how the universe expands, may be growing stronger over time, according to a new study.

Dark energy, discovered 20 years ago by scientists measuring the distances to supernovas, or exploding stars, is described as an energy of empty space that never changes over space and time. Researchers believe it represents about 70 percent of the total universe.

The study published this week in the peer-reviewed British journal Nature Astronomyinstead measures the distances to quasars, bright celestial objects located in the center of galaxies.

Using data from NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM-Newton observatory, researchers found the expansion rate of the universe is different from the model using supernovas.

“We observed quasars back to just a billion years after the Big Bang, and found that the universe’s expansion rate up to the present day was faster than we expected,” Guido Risalti, a study co-author from the department of physics and astronomy at the University of Florence in Italy, said in a statement. “This could mean dark energy is getting stronger as the cosmos grows older.”

Elisabeta Lusso of Durham University in the United Kingdom said because this technique for assessing dark energy is new, researchers took extra steps to make sure it was a reliable way to measure. “We showed that results from our technique match up with those from supernova measurements over the last 9 billion years, giving us confidence that our results are reliable at even earlier times,” she said.

Researchers say they used quasars to measure because they have a much farther reach compared to supernovas.

Adam Riess, a professor of physics and astronomy at Johns Hopkins University, said while the discovery would be “a really big deal” if confirmed, quasars have not proven to be historically reliable.

“People have not really used them as precision measuring tools for the universe because they have a very large dynamic range,” said Riess. “We don’t have a lot of confidence when we see one, we know how luminous it ought to be.”

Robert Kirshner, a Clowes Research Professor of Science, Emeritus at Harvard University, said that while the results of the study could prove true, there is no other evidence to date showing dark energy has changed with time.

“The thing that’s attractive about (their work) is that quasars are brighter, so you can see them farther back,” said Kirshner. “But you do worry the quasars from the early universe are not quite the same as the ones nearby.”

from:    https://www.usatoday.com/story/tech/news/2019/01/31/dark-energy-mysterious-force-space-growing-stronger-study/2732772002/