Researchers at Nagoya University and the University of Tokyo used the Subaru Telescope’s Hyper Suprime-Cam Survey to identify 1.5 million galaxies whose light has traveled for twelve billion years. Light travels at a set speed – about 300,000 km/s – and when we look at distant objects, we actually get to look back in time. Prior to this survey, galaxy research stopped with galaxies about eight billion years back; farther galaxies were just too faint to see.

The Subaru Telescope’s survey, however, got some help from galaxy clusters.

When a large mass is between us and a distant light source, that mass’s gravity can bend light just like a magnifying glass. This magnification allows us to see things we otherwise can’t.

And it isn’t just optical light that gets magnified. When we look carefully at the most distant light we can see – the cosmic microwave background radiation – we can see distorted places that are reshaped by the gravity of distant galaxies.

And… and… in this study, researchers used galaxy clusters to measure the light from galaxies from twelve billion years ago, and then they looked at the cosmic microwave background to see how those galaxies’ masses also distorted things.

Basically, thanks to a whole lot of gravity bending a whole lot of light, this team was able to measure how much light is coming from how much mass and then calculate how much dark matter is hanging out unseen.

This is amazing work. And it is amazing work that yields an unexpected result.

This team, led by Hironao Miyatake, found that the early universe wasn’t as clumped as expected.

We know the universe started out as a mostly smooth distribution of gas, and the tiniest fluctuations eventually turned into the galaxy clusters and voids we see in our modern universe. We have models that describe how we thought that would happen over time, and while the models mostly match, they don’t entirely match. If this research result stands up to further tests, this could help us fix those models.

This study, published in Physical Review Letters, only looked at one-third of the Subaru Hyper Suprime-Cam Survey. Future research will look at the rest of that survey, and we’ll bring it to you here when we learn more.

More Information

ICRR press release

“First Identification of a CMB Lensing Signal Produced by 1.5 Million Galaxies at z∼4: Constraints on Matter Density Fluctuations at High Redshift,” Hironao Miyatake et al., 2022 August 1, Physical Review Letters