Proper noun
Trumpler
A surname.
M46 is classified as a Shapley class f and a Trumpler class III 2 m cluster. Source: Internet
Under the Trumpler scheme, the Pleiades are classified as I3rn (strongly concentrated and richly populated with nebulosity present), while the nearby Hyades are classified as II3m (more dispersed, and with fewer members). Source: Internet
Open clusters are often classified according to a scheme developed by Robert Trumpler in 1930. Source: Internet