science & techESA/Hubble

Galactic treasure chest

the gist

Galaxy clusters are collections of thousands of galaxies held together by gravity, and they sit at the nodes of the cosmic web, the large-scale network of matter across the universe. Their huge mass bends spacetime, so they act as natural zoom lenses: light from more distant galaxies behind them is warped and magnified. This gravitational lensing lets astronomers see faint, very early galaxies that would otherwise be too dim to observe. The Hubble RELICS survey imaged 41 massive clusters to find the brightest distant galaxies for the James Webb Space Telescope to study.

so what

Lensing clusters are one of the best tools for studying the early universe and the distribution of dark matter. Using them as magnifiers lets telescopes reach galaxies that formed within the first few hundred million years after the Big Bang.

ESA/Hubble · CC BY 4.0

Image: ESA/Hubble & NASA, RELICS