This new image from the NASA/ESA Hubble Space Telescope is one of the best ever views of the massive galaxy cluster Abell 370. The image (hi-res version) is part of the Hubble Frontier Fields, a three-year, 840-orbit program, begun in 2013, that teams Hubble with NASA’s other space observatories to probe the early Universe by studying six different galaxy clusters.
With the final observation of the distant galaxy cluster Abell 370 — approximately 6 billion light-years away — the Frontier Fields program came to an end. Abell 370 is one of the very first galaxy clusters in which astronomers observed the phenomenon of gravitational lensing, the warping of spacetime by the cluster’s gravitational field that distorts the light from galaxies lying far behind it. This manifests as arcs and streaks in the picture, which are the stretched images of background galaxies. Image credit: NASA / ESA / Hubble / HST Frontier Fields.
Abell 370 is a cluster of hundreds of galaxies, located approximately 6 billion light-years away in the constellation Cetus.
Already in the mid-1980s higher-resolution images of the cluster showed that the giant luminous arc in the lower left of the image was not a curious structure within the cluster, but rather an astrophysical phenomenon: the gravitationally lensed image of a galaxy twice as far away as the cluster itself.
Hubble helped show that this arc is composed of two distorted images of an ordinary spiral galaxy that just happens to lie behind the cluster.
Abell 370’s gravitational influence warps the shape of spacetime around it, causing the light of background galaxies to spread out along multiple paths and appear both distorted and magnified. The effect can be seen as a series of streaks and arcs curving around the center of the image.
This image of Abell 370 was captured as part of the Frontier Fields program.
Six clusters of galaxies — Abell 370, Abell S1063, MACS J0416.1-2403, MACS J0717.5+3745, MACS J1149.5+2223, and Abell 2744 — were imaged in exquisite detail.
An earlier image of Abell 370 — using less observation time and therefore not recording such faint detail — was published in 2009.
During the cluster observations, Hubble also looked at six ‘parallel fields,’ regions near the galaxy clusters which were imaged with the same exposure times as the clusters themselves.
Each cluster and parallel field were imaged in infrared light by Hubble’s Wide Field Camera 3 (WFC3), and in visible light by its Advanced Camera for Surveys (ACS).
The Frontier Fields program produced the deepest observations ever made of galaxy clusters and the magnified galaxies behind them.
These observations are helping astronomers understand how stars and galaxies emerged out of the dark ages of the Universe, when space was dark, opaque, and filled with hydrogen.
Studying massive galaxy clusters like Abell 370 also helps with measuring the distribution of normal matter and dark matter within such clusters.
By studying its lensing properties, astronomers have determined that Abell 370 contains two large, separate clumps of dark matter, contributing to the evidence that this massive galaxy cluster is actually the result of two smaller clusters merging together.
Now that the observations for the Frontier Fields program are complete, astronomers can use the full dataset to explore the clusters, their gravitational lensing effects and the magnified galaxies from the early Universe in full detail.
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This article is based on a press-release from the National Aeronautics and Space Administration.
