Skip to comments.Astronomy Picture of the Day 1-09-03
Posted on 01/09/2003 3:48:17 AM PST by petuniasevan
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.
2003 January 8
Explanation: Two billion light-years away, galaxy cluster Abell 1689 is one of the most massive objects in the Universe. In this view from the Hubble Space Telescope's Advanced Camera for Surveys, Abell 1689 is seen to warp space as predicted by Einstein's theory of gravity -- bending light from individual galaxies which lie behind the cluster to produce multiple, curved images. The power of this enormous gravitational lens depends on its mass, but the visible matter, in the form of the cluster's yellowish galaxies, only accounts for about one percent of the mass needed to make the observed bluish arcing images of background galaxies. In fact, most of the gravitational mass required to warp space enough explain this cosmic scale lensing is in the form of still mysterious dark matter. As the dominant source of the cluster's gravity, the dark matter's unseen presence is mapped out by the lensed arcs and distorted background galaxy images.
Lensing at Abell 2218
Spiral galaxy lensing a quasar into 4 images. The galaxy is NOT near the quasar.
How Einstein would have loved seeing this.
Gravitational lenses are interesting and their existence a fairly recent addition to our knowledge; but, over on the other thread the National Radio observatory has used the phenomenon to measure the speed of gravity. Catch that?
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