Explanation:
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 the gravitational affect of a
central bar that has
since vanished.
The abovephoto 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 the Snake
(Serpens).
Coincidentally, visible in the gap
(at about one o'clock) is yet another
ring galaxy that likely lies
far in the distance.
