Largest-Ever Supernova Catalog Provides Further Evidence Dark Energy Is Weakening

Scientists using the largest-ever catalog of Type 1a supernovas -- cosmic explosions from white dwarf 'vampire stars' -- have uncovered further evidence that dark energy may not be constant. While the findings are still preliminary, they suggest the mysterious force driving the universe's expansion could be weakening, which 'would have ramifications for our understanding of how the cosmos will end,' reports Space.com. From the report: By comparing Type 1a supernovas at different distances and seeing how their light has been redshifted by the expansion of the universe, the value for the rate of expansion of the universe (the Hubble constant) can be obtained. Then, that can be used to understand the impact of dark energy on the cosmos at different times. This story is fitting because it was the study of 50 Type 1a supernovas that first tipped astronomers off to the existence of dark energy in the first place back in 1998. Since then, astronomers have observed a further 2,000 Type 1a supernovas with different telescopes. This new project corrects any differences between those observations caused by different astronomical instruments, such as how the filters of telescopes drift over time, to curate the largest standardized Type 1a supernova dataset ever. It's named Union3.

Union3 contains 2,087 supernovas from 24 different datasets spanning 7 billion years of cosmic time. It builds upon the 557 supernovas catalogued in an original dataset called Union2. Analysis of Union3 does indeed seem to corroborate the results of DESI -- that dark energy is weakening over time -- but the results aren't yet conclusive. What is impressive about Union3, however, is that it presents two separate routes of investigation that both point toward non-constant dark energy. 'I don't think anyone is jumping up and down getting overly excited yet, but that's because we scientists are suppressing any premature elation since we know that this could go away once we get even better data,' Saul Perlmutter, study team member and a researcher at Berkeley Lab, said in a statement. 'On the other hand, people are certainly sitting up in their chairs now that two separate techniques are showing moderate disagreement with the simple Lambda CDM model.'

And when it comes to dark energy in general, Perlmutter says the scientific community will pay attention. After all, he shared the 2011 Nobel Prize in Physics for discovering this strange force. 'It's exciting that we're finally starting to reach levels of precision where things become interesting and you can begin to differentiate between the different theories of dark energy,' Perlmutter said.

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