The final results from the Dark Energy Survey (DES) have provided exciting new clues about the mysterious ‘dark energy’ that is driving the accelerating expansion of the universe. Analysis of thousands of supernovae observed by the DES over 6 years has found no evidence that dark energy is getting diluted over time, as some theories had predicted. This suggests our universe may continue expanding steadily forever rather than ending in a ‘Big Rip’.
Steady Acceleration Versus a ‘Big Rip’ Fate
The DES examined over 5,000 type Ia supernovae – stellar explosions useful as ‘standard candles’ to measure cosmic distances. Combining this data with observations of the early universe from the Cosmic Microwave Background, the collaboration traced how quickly the expansion of the universe has accelerated over the last 10 billion years due to dark energy.
Some speculative theories suggested dark energy might become diluted or switch signs as the universe expands, causing a slower acceleration down the line. More dramatically, others proposed it may strengthen over time, eventually overcoming gravity and violently ripping apart galaxies, stars and even space-time itself in a ‘Big Rip’. But the new analysis found no significant change in dark energy over time, pointing instead to a steady acceleration that could continue indefinitely.
“The data favors a very simple model for dark energy where the energy density is constant over space and time,” says DES spokesperson Prof. Rich Kron from the University of Chicago. “This tells us the universe is likely to continue expanding forever, rather than ending in a Big Rip.” The findings will be published in 18 papers across several astronomy journals.
Challenges Remaining Big Bang and Inflation Models
The DES results also shed light on the very origins of the universe itself. Measurements of early density fluctuations that seeded modern cosmic structures match well with predictions from the theory of ‘inflation’ – a period of extremely rapid expansion in the first tiny fraction of a second after the Big Bang.
However, the team found a 2% mismatch between the predicted and observed density, which, although sounding small, significantly exceeds expectations. “It’s forcing us to go back to the early universe and understand the physics operating at that time,” says Kron. Reconciling this discrepancy may require tweaking theories around cosmic inflation or revising estimates of neutrino masses – hinting at new fundamental physics.
“Crowning Achievement” After 6 Years Observing Night Skies
The Dark Energy Survey was an international collaboration of 400 scientists using the Victor M. Blanco telescope in Chile over 6 years up to 2019. The telescope’s 570-megapixel Dark Energy Camera captured light from over 300 million galaxies, allowing scientists to trace cosmic expansion across a huge chunk of the observable universe.
“The DES has been an enormously successful dark energy experiment,” says Fermilab scientist and co-spokesperson Prof. Jim Annis. “The superb observations taken during six years of operation have allowed scientists from around the world to carry out studies ranging from discovering new dwarf satellite galaxies orbiting our Milky Way galaxy to making precision measurements of the universe’s first generation of galaxies.”
With the survey now complete, researchers are currently combing through the remaining trove of DES images, which contain clues about dark matter, galaxy formation, and the discovery of objects like exploding stars, supermassive black holes, distant galaxies and near-Earth asteroids.
“The team is currently working hard, analyzing the remaining data so that it can release catalogs of distant galaxies and gravitationally lensed galaxies to the astronomical community,” says Annis. “But the COSMO sample of supernovae marks the end of data collection for the original survey and the crowning achievement of six years’ work to capture the beauty of the night sky.”
Legacy Survey To Pick Up Where DES Left Off
The productive 6 years of sky observations by the Dark Energy Survey have now concluded, but an even more ambitious cosmic survey is slated to pick up where DES left off. The Legacy Survey of Space and Time (LSST) based in Chile will commence full operations later this year using an enormous 3.2-gigapixel camera that can capture the entire southern night sky twice per week.
“LSST will enable an enormous range of phenomenal cosmic surveys, dwarfing all current projects, including DES, by an order of magnitude or more,” says LSST Director Prof. Steve Kahn. “It aims to unravel mysteries from mapping tiny Kuiper Belt objects to the discovery and monitoring of rapidly exploding supernovae and gamma ray bursts.” Over a 10-year period, LSST is expected to gather 50 trillion bytes of data leading to new insights about dark energy, dark matter, near-earth asteroids, exoplanets and more, cementing humanity’s place as a truly spacefaring species.
- Analysis of 5000 supernovae in the Dark Energy Survey found no evidence that cosmic acceleration is slowing over time
- This suggests a steady expansion likely to continue indefinitely rather than a ‘Big Rip’
- But a small mismatch with early universe models may require revising physics around inflation
- The 6-year survey using a 570-megapixel camera was highly successful, with more discoveries still to come
- An even larger 10-year Legacy Survey of Space and Time now prepares to pick up the baton
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