Abell 370 Parallel
This is a Hubble Space Telescope view of a random patch of sky that reveals how the universe looks at large: a "wallpaper" of innumerable galaxies spread across space and time. They offer a wide assortment of majestic star cities that vary in age, shape, and stellar populations. It’s a narrow view down a corridor that stretches back in time for billions of years.
The wide range of rich colors comes from the fact that this snapshot is assembled from images taken in visible light as well as near-infrared light. The reddest objects in the image are presumably the farthest galaxies, whose light has been stretched into the red part of the spectrum by the expansion of space. The yellow objects are massive football-shaped elliptical galaxies that contain older stellar populations. The blue galaxies are disk-shaped pinwheels of ongoing star formation. The entire field is peppered with much smaller, fragmentary, blue galaxies – the "building blocks" ancestors of majestic spiral galaxies like our Milky Way.
This so-called "parallel field" was taken while Hubble was looking at the primary target, a massive foreground galaxy cluster, while another camera simultaneously viewed the adjacent, seemingly sparse patch of sky.
Such parallel fields increase the efficiency of Hubble for deep sky surveys, and yield new insights into the evolution of galaxies over billions of years.