GLOBULAR CLUSTERS ARE impressively dense, spherical collections of stars typically found in the halos of spiral galaxies. We inherit the term from William Herschel’s paper ‘On the Construction of the Heavens,’ published in 1785 in the Philosophical Transactions of the Royal Society of London, in which he described a group of objects that “form themselves into a cluster of stars of almost a globular figure”.
Of the roughly 190 globular clusters associated with our galaxy, about 40% are found in some of the richest parts of the winter Milky Way. In 1918, the American astronomer Harlow Shapley mapped the distribution of globular clusters to determine the Sun’s position within the galaxy. He correctly deduced the location of the galactic centre — pinpointing it in Sagittarius — based on the high concentration of globular clusters found in that direction. He also demonstrated that our Sun isn’t located at the galaxy’s core as star surveys implied at the time, but instead is in the disk some 27,000 light-years from the centre. This was a significant milestone in our understanding of the cosmos.
It’s no surprise, then, that more than half the globular clusters listed in the Messier catalogue lie in Sagittarius, Ophiuchus and Scorpius. Many of the 16 Messier globulars are well-known telescopic favourites. The New General Catalogue of Nebulae and Clusters of Stars records a similar proportion of globulars in the same area of the sky. In this celestial tour, we’ll explore some of the more interesting globular clusters in the winter Milky Way that didn’t make Messier’s list.
