NASA’s Hubble Space Telescope team of scientists from NASA have discovered that the universe is expanding 5 percent to 9 percent faster than previously thought.
“This surprising finding may be an important clue to understanding those mysterious parts of the universe that make up 95 percent of everything and don’t emit light, such as dark energy, dark matter, and dark radiation,” said Nobel Laureate Adam Riess of the Space Telescope Science Institute and the Johns Hopkins University, based in Baltimore, Maryland.
The team led by Riess used refined techniques to make an accurate calculation of the universe’s current expansion rate. It has reduced the uncertainty rate to only 2.4%. They found that Type Ia supernovae, a commonly used cosmic yardstick, are exploding with huge brightness that is enough to be seen from relatively longer distances.
They were able to measure about 2,400 Cepheid stars in 19 galaxies and compared the findings with Type Ia supernovae’s galaxies. Using the two values, they calculated how fast the universe expands with time or the Hubble constant.
The Hubble constant value is 73.2 km/sec per megaparsec. (A megaparsec equals 3.26 million light-years.) The new value means the distance between cosmic objects will double in another 9.8 billion years.
This refined calibration presents a puzzle, however, because it does not quite match the expansion rate predicted for the universe from its trajectory seen shortly after the Big Bang, said Reiss.
There are a few possible explanations for the universe’s excessive speed. One possibility is that dark energy, already known to be accelerating the universe, may be shoving galaxies away from each other with even greater.
Another idea is that the cosmos contained a new subatomic particle in its early history that traveled close to the speed of light, called “dark radiation” and leading to additional dark radiation that could be leading to today’s expansion rate from its post-big bang trajectory.
And finally, the speedier universe may be telling astronomers that Einstein’s theory of gravity is incomplete.
“We know so little about the dark parts of the universe, it’s important to measure how they push and pull on space over cosmic history,” said Lucas Macri of Texas A&M University in College Station, one of the team members.
The results will appear in an upcoming issue of The Astrophysical Journal.