(Section Not Complete)
Open cluster with associated nebula
(This is M16---the Eagle Nebula)
Pleiades open cluster
Open and globular clusters in the Messier catalog
Here is an
open cluster M50, which is 3000 light years from Earth and is about 20
light years across. Open clusters such as this one have some common
In images of open clusters such as this one, not all stars in
the field of view are members of the cluster; some are stars between us and the
cluster and some are stars beyond the cluster. One way to distinguish
members of the cluster from stars that just happen to lie in the
is by measuring their proper motion on the celestial sphere.
The stars in the cluster must all have approximately
the same proper motion or the
cluster would have dissipated over time, but stars not associated with the
cluster would be expected to have more random motions.
Open clusters are preferentially found in the plane of the
galaxy (thus they are also called galactic clusters); in contrast, the
globular clusters are concentrated in the halo of the galaxy and can be very
far out of the plane.
- Open clusters tend to be more
irregular in shape than the highly symmetric globular clusters.
- Open clusters typically contain of
order 100 stars, as compared with as many as hundreds of thousands in globular
Here is a synopsis
of what the colors of stars in the cluster M50 can tell us about astrophysics.
Here is a set of links to images of
In the center of 30
"lies a huge cluster of the largest, hottest, most massive stars
known. R136 is composed of thousands of hot blue stars, some about 50 times
more massive than our
Sun. Although the
ages of stars in R136 cause it to be best described as an open cluster, R136's
density will likely make it a low
mass globular cluster in a few billion years."