|NGC 660 lies near the center of
swimming in the boundaries of the constellation
Over 20 million light-years away, its peculiar appearance marks it as
a polar ring galaxy.
A rare galaxy type, polar ring galaxies have a substantial population
of stars, gas, and dust
orbiting in rings nearly perpendicular
to the plane of the galactic disk.
configuration could have been caused by the chance capture
of material from a passing galaxy by the disk galaxy, with the captured
debris strung out in a rotating ring.
ring component can be used
to explore the shape of the galaxy's otherwise unseen
halo by calculating the
dark matter's gravitational
influence on the rotation of the ring and disk.
Broader than the disk, NGC 660's ring spans about 40,000 light-years.