The Trumpler Classification

The Trumpler Type

The Trumpler classification system of open clusters was invented by R.J. Trumpler. The classification is based on three parameters:

I.

II.

III.

IV.

Detached clusters with strong central concentration.

Detached clusters with little central concentration.

Detached clusters with no noticeable concentration.

Not well detached from surrounding star field.

1.

2.

3.

Most of the cluster stars are nearly the same apparent brightness.

Moderate range in brightness.

Cluster is composed of bright and faint stars.

p.

m.

r.

Poor (less than 50 stars).

Medium rich (50-100 stars).

Rich (more than 100 stars).

Image Data

The above image shows twelve open clusters, sorted by the degree of concentration (horizontally) and sorted by the richness of stars (vertically). The range of brightness of all shown clusters is 2 or 3.

Source: WEBDA (Lynga catalogue)

The following links give detailed information about the cluster images.