Polar Ring Galaxy NGC
660
From NASA’s Astronomy Picture of the Day
NGC 660 is featured in this cosmic snapshot, a sharp
composite of broad and narrow band filter image data from the Gemini North
telescope on Mauna Kea.
Over 20 million
light-years away and swimming within the boundaries of the constellation Pisces,
NGC 660's 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.
The bizarre-looking configuration could
have been caused by the chance capture of material from a passing galaxy by a
disk galaxy, with the captured debris eventually strung out in a rotating ring.
The violent
gravitational interaction would account for the myriad pinkish star forming
regions scattered along NGC 660's ring.
The
polar ring component can also be used to explore the shape of the
galaxy's otherwise unseen dark matter 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 over 50,000 light-years.
