Hoag's Object: A Strange
Ring Galaxy
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 effect of a central
bar that has since vanished.
The photo below taken by the Hubble
Space Telescope in July 2001
revealed unprecedented details of Hoag's Object. More recent observations in
radio waves indicate that Hoag's Object has not accreted a smaller galaxy in the
past billion years.
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.
Image Credit: Credit: R. Lucas (STScI/AURA), Hubble Heritage Team, NASA
