When did these big galaxies first begin to dance? Really only four of the
five of Stephan’s Quintet are locked in a cosmic
tango of repeated close encounters taking place some 300 million light-years away. The odd galaxy out is easy
to spot in this recently reprocessed image by the Hubble
Space Telescope — the interacting galaxies, NGC 7319, 7318B, 7318A, and
7317 (left to right), have a more dominant yellowish cast. They also tend to
have distorted loops and tails,
grown under the influence of disruptive
gravitational tides. The mostly bluish galaxy, large NGC 7320 on the
lower left, is in the foreground at about 40 million light-years distant, and
so is not part of theinteracting group. Data and modeling indicate
that NGC 7318B is a relatively new intruder. A recently-discovered halo of old red stars
surrounding Stephan’s Quintet indicate that at least
some of these galaxies started tangling over a billion years. Stephan’s
Quintet is visible with a moderate sized-telescope toward the
constellation of Winged Horse (Pegasus).
Image Credit: NASA, ESA, Hubble; Processing: Daniel
Nobre
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