Helix Galaxy (NGC 2685)
The Helix Galaxy (NGC 2685) is an unusual lenticular galaxy in
the constellation Ursa Major that is a member
of the very rare class of polar ring
galaxy; it is also known as the Pancake Galaxy. Several
thin filamentary strands, consisting of knots of luminous star-forming regions
and hydrogen gas, with a diameter comparable to the main disk, form a helical
band perpendicular to the main disk and centered on the galactic nucleus.
These structures suggest that NGC 2685 once had a companion, perhaps like
one of the Milky Way's Magellanic
Clouds, that was captured into a polar orbit and had its stars eventually
merged with those of the larger system, leaving behind the companion's interstellar
medium. New generations of stars formed from this material to produce
the luminous ring seen today. It is possible that if the Magellanic Clouds
had been closer to the Milky Way, they too would have created a polar ring
around our galaxy. Perhaps a foreshadowing of this process can be found
in the so-called Magellanic Stream,
a string of hydrogen clouds trailing the Magellanic clouds and extending
thousands of light-years along their orbit of the Milky Way.
||5.0' × 1.5'
||R.A. 08h 55.6m, Dec. +58° 44'