NGC 188 -- Open Cluster in Cepheus
A Skeletal Wrist and Fingers
Everything about NGC 188 seems off. It is the furthest north of any NGC object (only four
degrees from Polaris) and it is an Open Cluster. That just isn’t right! Open Clusters are in
a galaxy’s spiral arms where star formation “normally occurs” not isolated in star poor regions
like that found in the far northern region of Cepheus. And NGC 188 is old, very old for an
Open Cluster. At 6 billion years of age most Open Clusters have long since been pulled apart
by irregularities in their gravitational makeup.
NGC 188 is often referred to as the Polarissim Cluster because of its proximity to the north
celestial pole (it is the northern most star cluster in the night sky). None of its stars are bright
-- but there are lots of them. In my 110mm refractor the brighter members are barely visible,
while the light of the vast majority of them blend together to create an irregular shaped glow
that to me appears like ethereal appendages or fingers.
Much of the mystery surrounding NGC 188 can be explained if it did not actually form in our
galaxy. Recent information suggests that when small galaxies are torn apart by much larger
galaxies that their remnants often form large filaments extending into space forming
starry/gaseous arcs around or away from the host galaxy. It is now thought that NGC 188 is
part of the Monoceros Stream (also called the Monoceros Ring) which was an ancient dwarf
galaxy that was devoured by the Milky Way Galaxy (see Kanipe & Webb’s Annals of the
Deep Sky, Volume 5, page 250, for additional details).
Stephen O’Meara, once wrote that NGC 188 appeared to him as a “skeletal wrist and
fingers”. If it is true that this strange misplaced star cluster is a tiny remnant of a once living
galaxy that was long ago torn apart by our Milky Way, then his analogy/description is a good