The Large Magellanic Cloud is brimming with open clusters

The Large Magellanic Cloud is exceptionally rich in open clusters, and a large number of catalogues have been published since James Dunlop, observing the southern skies from the Brisbane observatory at Paramatta, New South Wales, Australia during the years 1823-1827, published A Catalogue of Nebulae and Star Clusters in the Southern Hemisphere observed in New South Wales. The most complete catalogue is that of Bica et al. (2008), which records a mammoth 3,086 star clusters, excluding associations. (The authors suggested that the catalogue is still not complete and a large number of poor clusters are yet to be identified!)

It certainly gives us a fabulous collection to observe – over 600 are included! And there are open clusters for everyone… from those that are gorgeous, and bright and with resolved stars, all the way through the entire observing gamut to those that are exceedingly small and faint, and offer a very satisying challenge to locate and observe.

Among the clusters are a large number of binary clusters, which appear common the LMC, although they are extremely rare in our own galaxy. They are listed in a separate database. The compact clusters (clusters so tight that they masquerade as stars but in fact contain multiple components) are also listed separately.

NGC Open Clusters

James Dunlop, observing the southern skies from the Brisbane observatory at Paramatta, New South Wales, Australia during the years 1823-1827 discovered 30 open clusters in the Large Magellanic Cloud. John Herschel, observing from the Cape Of Good Hope during the years 1834–1838, discovered an additional 213 clusters (as well as observing those recorded by Dunlop).

IC Open Clusters

DeLisle Stewart (1870–1941) was an American astronomer. In 1896 he became a staff member of Harvard College Observatory, and from 1898 to 1901 he worked at that observatory’s station at Arequipa, Peru.

Pietro Baracchi discoveries with the Great Melbourne Telescope (1883-1893)

Pietro Baracchi (1851-1926) was an Italian-born astronomer who worked at Melbourne Observatory and he was the principal observer from September 1883 until 1893. His discoveries went unnoticed until 2018, when Steve Gottlieb ploughed through Baracchi’s observing logs. He discovered that Baracchi had made no less than 57 discoveries that are not in the NGC, of which 9 were Large Magellanic Cloud discoveries! As Steve noted, “It’s really a shame that neither he nor the director of the observatory (Robert Ellery) published these discoveries in one of the journals of the day, or at least passed them on to Dreyer to include in the NGC. That might have changed the general perception of abject failure of the telescope.”

1960: Paul Hodge

Acronym: H60b

In 1960, Paul Hodge published a catalogue of 35 clusters of the Large Magellanic Cloud that can be considered genuine globular clusters on the basis of their uncalibrated colour-magnitude diagrams. Of these, Hodge 11 has turned out to be the gorgeous bone fide ancient globular cluster (over 12 billion years old); the others have subsequently turned out to be open clusters.

Harlow Shapley and Eric Lindsay, 1963

Acronym: SL

In 1963, Harlow Shapley and Eric Lindsay published a catalogue consisting of 898 LMC clusters, based on searches of ADH Schmidt plates. The listed objects lie between RA 4h24m and 6h34m, and Dec. -63° and -75°. Their catalogue covers the whole range of morphologies, from the large bright aggregations now known as stellar associations, through the dense swarms of stars we recognize as globular clusters, to the smaller gatherings which are the counterparts of our galactic clusters (open clusters). Many of their clusters were subsequently discovered to be background galaxies as distinguishing between small clusters and background galaxies was a limitation of their plate material. Surprisingly, many of their clusters are considerably brighter and larger than many of the small, faint NGC objects in the Cloud.