What are we actually seeing when we look at one of the Frontier Fields images? The gravitational lensing that produces the strange, almost artistic-looking effects in the images — the streaks and blobs of light among glowing galaxies – is visually striking, but little of it falls into typical expectations of what we see when we look into the universe.
Archival image of the Abell 2744 cluster taken with Hubble’s visible light ACS instrument.Credit: NASA, ESA, and R. Dupke (Eureka Scientific, Inc.), et al.
Let’s break it down by examining this image of galaxy cluster Abell 2744, also known as Pandora’s Cluster. Four separate galaxy clusters containing several hundred galaxies are colliding in this image, providing the vast amount of mass — both normal and, most importantly, dark matter — needed to create a gravitational lens. The galaxies’ mass warps space and brightens, distorts and magnifies the light of nearly 3,000 galaxies located much farther away, behind the cluster.
For simplicity’s sake we’ve highlighted a representative sample of objects in the image. The highlighting therefore doesn’t capture every single object — just a handful of good examples.
In this image, the white circles enclose stars in our own Milky ...