The cluster of galaxies Abell 315

This wide-field, deep image reveals thousands of galaxies crowding an area on the sky roughly as large as the full Moon. These galaxies span a vast range of distances from us. Some are relatively close, as it is possible to distinguish their spiral arms or elliptical halos, especially in the upper part of the image. The more distant, instead, appear just like faint blobs — their light has travelled through the Universe for eight billion years or more before reaching Earth. Beginning in the centre of the image and extending below and to the left, a concentration of about a hundred yellowish galaxies identifies a massive galaxy cluster, designated Abell 315, about two billion light-years away from us. To complement the enormous range of cosmic distances and sizes surveyed by this image, a handful of objects much smaller than galaxies and galaxy clusters and much closer to Earth are dotted throughout the field: besides several stars, many asteroids are also visible as blue, green or red trails.

This image has been taken with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. It is a composite of several exposures acquired using three different broadband filters, for a total of almost one hour in the B filter and about one and a half hour in the V and R filters. The field of view is 34 x 33 arcminutes.