A cluster of galaxies fills the frame. A purple glow around the largest concentrations of galaxies indicates the distribution of dark matter.

Mass map of Abell 1689

Abell 1689 is an immense cluster of galaxies located 2.2 billion light-years away. Astronomers map the cluster's dark matter by plotting the arcs produced by light from background galaxies that are warped by the foreground cluster's gravitational field.

Credits: NASA, ESA, E. Jullo (Jet Propulsion Laboratory), P. Natarajan (Yale University), and J.-P. Kneib (Laboratoire d'Astrophysique de Marseille, CNRS, France); Acknowledgment: H. Ford and N. Benetiz (Johns Hopkins University), and T. Broadhurst (Tel Aviv University)
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TakenAugust 19, 2010
Image CreditNASA, ESA, E. Jullo (Jet Propulsion Laboratory), P. Natarajan (Yale University), and J.-P. Kneib (Laboratoire d'Astrophysique de Marseille, CNRS, France); Acknowledgment: H. Ford and N. Benetiz (Johns Hopkins University), and T. Broadhurst (Tel Aviv University)
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