Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

January 11, 1998
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Abell 2218: A Galaxy Cluster Lens
Credit: W. Couch (University of New South Wales), R. Ellis (Cambridge University), NASA

Explanation: Gravity can bend light. Almost all of the bright objects in this Hubble Space Telescope image are galaxies in the cluster known as Abell 2218. The cluster is so massive and so compact that its gravity bends and focuses the light from galaxies that lie behind it. As a result, multiple images of these background galaxies are distorted into faint stretched out arcs - a simple lensing effect analogous to viewing distant street lamps through a glass of wine. The Abell 2218 cluster itself is about 3 billion light-years away in the northern constellation Draco.

Tomorrow's picture: The Keyhole Nebula

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
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