Cluster of galaxies

A Gravitational Lens...

This photo taken with the Hubble Space Telescope shows a cluster of galaxies. Each of the bright rounded objects contains billions of stars. The huge concentrated mass of the cluster warps space around it, bending the light that comes through from galaxies lying far beyond the cluster. Each of the streaks and arcs in the photo is a smeared-out image of one of those distant galaxies.

Measuring the streaks and applying Einstein's equations, physicists can calculate the distribution of matter in this cluster of galaxies. Astronomers are also using the cluster itself as a sort of telescope. This powerful "gravitational lens" gathers light from galaxies so remote that we could not see them by other means. Some of the light you see here originated when the universe was barely a quarter of its present age.

You can EXIT to NASA's page about this picture
or EXIT to a guide to Einstein's general relativity (NCSA).
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Courtesy NASA.
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