New research involving "exploding stars" suggests the universe is not expanding as quickly as we thought it was.
Scientists found type Ia supernovae, or exploding stars, vary in brightness, as opposed to being rigidly uniform as was previously believed, the University of Arizona reported.
"We found that the differences are not random, but lead to separating Ia supernovae into two groups, where the group that is in the minority near us are in the majority at large distances - and thus when the universe was younger," said UA astronomer Peter A. Milne. "There are different populations out there, and they have not been recognized. The big assumption has been that as you go from near to far, type Ia supernovae are the same. That doesn't appear to be the case."
The finding provides insight into the widely accepted view that the universe is expanding at an accelerating rate, and is being pulled apart by dark energy. The supernovae that are dimmer are believed to have moved farther away from Earth that they should have if the universe expanded at the same rate. This suggests the rate at which stars are moving away from each other is increasing, meaning something must be pushing them apart.
"The idea behind this reasoning is that type Ia supernovae happen to be the same brightness -- they all end up pretty similar when they explode. Once people knew why, they started using them as mileposts for the far side of the universe," Milne said. "The faraway supernovae should be like the ones nearby because they look like them, but because they're fainter than expected, it led people to conclude they're farther away than expected, and this in turn has led to the conclusion that the universe is expanding faster than it did in the past."
The findings were published in a recent edition of the journal Astrophysical Journal.
