Alpha Persei Moving Cluster (Melotte 20) in Perseus
Alpha Persei Moving Cluster
The brightest star in the constellation of Perseus is Morphia which translates to the
“Elbow Nearest the Many Little Ones”. It is the bright star at the center of my drawing.
The elbow, of course, belongs to the Greek hero Perseus who killed Medusa and saved
Andromeda from the hideous Sea Monster.
Surrounding Morphia is an Open Cluster of approximately 50 type “O” and “B” stars.
These are very luminous and somewhat short-lived stars. This association of stars
around Morphia are likely the “Many Little Ones” referred to in its name. They are now
referred to as the “Alpha Perseid Moving Cluster” and are best seen with the unaided
eye away from city lights or through binoculars. Even from the suburbs this cluster shows
an impressive number of stars in a pair of binoculars and is well worth a look.
Through a telescope the field-of-view is too narrow and the 5-degree-sized cluster (10x
the size of the full moon) esthetically diminishes – and therefore is again, best enjoyed in
binoculars. Even in my fast 85mm refractor, where I can obtain a 4.7-degree field-of-view
the cluster losses much of its beauty. To complete this sketch, I made three separate
drawings at the scope and combined them into the final rendition to approximate the view
as seen through a large pair of binoculars from the suburbs.
These 50 or so bright stars are referred to as a Moving Cluster because all its members
are moving together at a rate of 10 miles per second. But you need not rush in finding the
cluster because at that speed it will still take around 90,000 years for the cluster to move a
single degree in the sky.