One-percent measure of the universe constrains dark energy

One-percent measure of the universe constrains dark energy

A universe might not be flat if dark energy was distributed unevenly throughout it, warping the curvature of spacetime.

Dark energy is an enigmatic force that humans can’t see, but that scientists believe is responsible for the universe expanding at an accelerating rate. Now, thanks to an ultraprecise new galaxy map, astronomers may be able to shed some light on the curious energy that makes up so much of the universe’s mass.

A research team working with the Baryon Oscillation Spectroscopic Survey (BOSS) has figured out the distances to galaxies more than 6 billion light-years away to within 1 percent accuracy, a feat never before accomplished in the science. They reported their findings on Jan. 8 at the American Astronomical Society.

“There are not many things in our daily lives that we know to 1-percent accuracy,” said David Schlegel, a physicist at Lawrence Berkeley National Laboratory and the principal investigator of BOSS. “I now know the size of the universe better than I know the size of my house.”

Scientists worked with BOSS to map out all 1.2 million galaxies they had. In doing so, the team found that the new measurements support the concept of the “cosmological constant” which Albert Einstein first proposed. The concept states that dark energy has remained constant throughout the universe’s history.

“We don’t yet understand what dark energy is, but we can measure its properties,” said Daniel Eisenstein, a Harvard University astronomer working with the survey. “Then, we compare those values to what we expect them to be, given our current understanding of the universe. The better our measurements, the more we can learn.

According to the research team, the new results are the best way to determine the curvature of space. The universe looks “flat;” its shape denotes which straight lines are parallel and the triangle’s angles add up to 180 degrees.

“One of the reasons we care is that a flat universe has implications for whether the universe is infinite,” Schlegel said. “That means — while we can’t say with certainty that it will never come to an end — it’s likely the universe extends forever in space and will go on forever in time. Our results are consistent with an infinite universe.”

BOSS astronomers make their observations by using a spectrograph on the Sloan Foundation’s 2.5-meter telescope at Apache Point Observatory in New Mexico.

“On a clear night when everything goes perfectly, we can add more than 8,000 galaxies and quasars to the map,” said Kaike Pan, who leads the team that works with the spectrograph.

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