In the center of this image, taken with the NASA/ESA Hubble Space Telescope,
is the galaxy cluster SDSS J1038+4849 — and it seems to be smiling.
You can make out its two orange eyes and white button nose. In the case of
this “happy face”, the two eyes are very bright galaxies and the misleading
smile lines are actually arcs caused by an effect known as strong gravitational
lensing.
Galaxy clusters are the most massive structures in the Universe and exert
such a powerful gravitational pull that they warp the spacetime around them and
act as cosmic lenses which can magnify, distort and bend the light behind them.
This phenomenon, crucial to many of Hubble’s discoveries, can be explained by
Einstein’s theory of general relativity.
In this special case of gravitational lensing, a ring — known as an Einstein
Ring — is produced from this bending of light, a consequence of the exact and
symmetrical alignment of the source, lens and observer and resulting in the
ring-like structure we see here.
Hubble has provided astronomers with the tools to probe these massive
galaxies and model their lensing effects, allowing us to peer further into the
early Universe than ever before. This object was studied by Hubble’s Wide Field
and Planetary Camera 2 (WFPC2) and Wide Field Camera 3 (WFC3) as part of a
survey of strong lenses.
A version of this image was entered into the Hubble’s Hidden Treasures image
processing competition by contestant Judy Schmidt.
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