Explanation:
Astronomers turn detectives when trying to
figure out the cause of startling sights like
NGC 1316.
Their investigation indicates that
NGC 1316
is an enormous
elliptical galaxy
that started, about 100 million years ago, to devour a smaller
spiral galaxy neighbor,
NGC 1317, just above it.
Supporting evidence includes the dark
dust lanes
characteristic of a
spiral galaxy,
and faint swirls of stars and gas visible in this
wide and deep image.
What remains unexplained are the unusually small
globular star clusters,
seen as faint dots on
the image.
Most elliptical
galaxies have
more and brighter globular
clusters than
NGC 1316.
Yet the observed
globulars are too old to have been
created by the recent
spiral collision. One
hypothesis is that these
globulars
survive from an even earlier galaxy
that was subsumed into
NGC 1316.
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