A non-typical galaxy of the type known as a ring galaxy, the appearance
of Hoag’s Object has interested amateur astronomers as much as its
uncommon structure has fascinated professionals. Is this one galaxy or
two? This question came to light in 1950 when astronomer Art Hoag
chanced upon this unusual extragalactic object. On the outside is a ring
dominated by bright blue stars, while near the center lies a ball of
much redder stars that are likely much older. Between the two is a gap
that appears almost completely dark. How Hoag’s Object formed remains
unknown, although similar objects have now been identified and
collectively labeled as a form of ring galaxy. Genesis hypotheses
include a galaxy collision billions of years ago and perturbative
gravitational interactions involving an unusually shaped core. The above
photo taken by the Hubble Space Telescope in July 2001 reveals
unprecedented details of Hoag’s Object and may yield a better
understanding. Hoag’s Object spans about 100,000 light years and lies
about 600 million light years away toward the constellation of Serpens.
Coincidentally, visible in the gap is yet another ring galaxy that
likely lies far in the distance.
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