Astronomers have put together one of the most comprehensive maps of all the matter in the universe. The huge undertaking hints at a slightly smoother universe than we thought, suggesting that something might be missing from our models.
The widely accepted theory is that the Big Bang kicked off everything by sending matter flying out in all directions into the expanding universe. As you might expect, it didn’t all spread out evenly but had an element of randomness to it, so certain regions had more matter than others. Over time, denser regions began to form clouds of dust and gas, which went on to condense into stars, galaxies and everything else.
By studying the distribution of matter in the cosmos today, scientists can get a better understanding of the forces that shape the universe. That includes such mysteries as dark energy, which is believed to be driving the expansion of the universe to accelerate over time.
Now scientists have made one of the most precise maps of the universe’s matter to date. Doing so involved collecting huge amounts of data from two different telescope surveys and cross-checking them against each other, which helps reduce the likelihood of any errors in one dataset interfering with the results.
The first is the Dark Energy Survey, a project that spent six years scanning the sky in near-ultraviolet, visible and near-infrared light from its high-altitude perch in Chile. The second is the South Pole Telescope, which studies the cosmic microwave background (CMB) – the afterglow of the Big Bang.
To map out the matter, the scientists focused on a phenomenon called gravitational lensing. Essentially, objects with huge masses will actually warp spacetime itself to the point that the path of light will be bent as it passes by. Measuring the extent of this bending can allow scientists to calculate how much mass, and therefore matter, is present in a particular region.
The analysis mostly lined up with what’s currently the most widely accepted model of the universe, known as the lambda cold dark matter (ΛCDM) model. However, it might not have been a perfect fit – the study suggests that matter clumps together a little less than we thought, which could open the door for a whole new model to explain things better.
“It seems like there are slightly less fluctuations in the current universe than we would predict assuming our standard cosmological model anchored to the early universe,” said Eric Baxter, an author of the studies.
This isn’t the first crack to appear in our so-called standard model of cosmology. ΛCDM requires the existence of a mysterious substance called dark matter, which can only be observed through its gravitational influence on regular matter. However, as sure as astronomers are that it exists, decades of experiments have failed to directly detect it.
There’s also a problem called the Hubble tension. Basically, observing the cosmos in one way results in a specific value for what’s called the Hubble constant – but the ΛCDM model, backed up by other methods of observation, results in a completely different value. Stranger still, both are increasingly more certain, and yet there’s no overlap, suggesting the possibility of new physics.
That said, the researchers on the new project acknowledge that their observations of the less clumpy nature of matter haven’t yet reached the level of statistical significance needed to be certain. Future work could help confirm this.
Either way, this new map of the universe’s matter will provide a good foundation for future study.
The research was published in three papers in the journal Physical Review D.
Source: University of Chicago
