Globular Clusters of the Milky Way

All 201 known globular clusters of the Milky Way

The list follows William Harris's catalog of Milky Way globular clusters with distances from Holger Baumgardt and Eugene Vasiliev (2021), plus clusters found since, many of them hidden behind dust near the galactic center. Sort any column, or type a name or constellation. The buttons above the map filter by distance. Clusters with their own page on Go Astronomy link to it.

The globular clusters center on a point about 23,600 light-years away in Sagittarius: the center of the Milky Way

101 of the 201 clusters are in just three constellations, Sagittarius, Scorpius and Ophiuchus. Put each cluster in three dimensions from its direction and distance, and the average position of all 199 lies 23,600 light-years from us toward Sagittarius. The clusters orbit the center of the galaxy, so their center is the galaxy's center; the modern measured distance is about 26,700 light-years.

Harlow Shapley made this argument in 1918 with the clusters he could measure, and it moved the Sun from the middle of the galaxy to its outskirts. His distance was too large, about 50,000 light-years, because dust dims the clusters and he did not correct for it.

46 globular clusters hold pulsars, and some are the cores of captured galaxies

Stars are packed so tightly in a globular cluster's core that they meet and pair up. Neutron stars spun up by a companion become millisecond pulsars, and clusters hold far more of them per star than the rest of the galaxy. Clusters with known pulsars include Omega Centauri (NGC 5139), 47 Tucanae (NGC 104), Messier 22 (Sagittarius Cluster), NGC 6752 (Great Peacock Globular), Messier 4, Messier 5, NGC 6397 (Caldwell 86), Messier 13 (Hercules Cluster), Messier 3, Messier 15 (Pegasus Cluster).

Black holes have been reported in 47 Tucanae (NGC 104), Messier 15 (Pegasus Cluster), Messier 4, NGC 3201 (Caldwell 79), NGC 6397 (Caldwell 86), Omega Centauri (NGC 5139).

Some clusters were not born in the Milky Way. They are the dense centers of small galaxies that the Milky Way pulled apart:

• FSR 1758: core of the Sequoia Dwarf Galaxy
• Messier 54: core of the Sagittarius Dwarf Galaxy
• NGC 1851: core of the Canis Major Dwarf Galaxy
• NGC 2808: core of the Sausage Dwarf Galaxy
• Omega Centauri (NGC 5139): thought to be the core of a captured dwarf galaxy

Others are notable for what is inside them:

• Messier 15 (Pegasus Cluster): a planetary nebula among its stars
• Messier 22 (Sagittarius Cluster): a planetary nebula among its stars
• Messier 4: a planet, in orbit around a pulsar and white dwarf pair
• Messier 62 (Flickering Globular): a planet, in orbit around a pulsar and white dwarf pair
• NGC 6441 (Silver Nugget Cluster): a planetary nebula among its stars
• Palomar 6: a planetary nebula among its stars

112 globular clusters are brighter than magnitude 10

The brightest are visible in binoculars as fuzzy stars; a 6-inch telescope begins to resolve the edges of M13 and M22 into stars, and an 8-inch or larger shows many of them as balls of stars. Most of the rest are faint, small and far away. The twenty brightest:

1. Omega Centauri NGC 5139, in Centaurus, magnitude 3.7, 17,700 light-years
2. 47 Tucanae NGC 104, in Tucana, magnitude 4.0, 14,700 light-years
3. Messier 22 Sagittarius Cluster, in Sagittarius, magnitude 5.1, 10,800 light-years
4. NGC 6752 Great Peacock Globular, in Pavo, magnitude 5.4, 13,400 light-years
5. Messier 4, in Scorpius, magnitude 5.6, 6,030 light-years
6. Messier 5, in Serpens, magnitude 5.7, 24,400 light-years
7. NGC 6397 Caldwell 86, in Ara, magnitude 5.7, 8,090 light-years
8. Messier 13 Hercules Cluster, in Hercules, magnitude 5.8, 24,200 light-years
9. Messier 3, in Canes Venatici, magnitude 6.2, 33,200 light-years
10. Messier 15 Pegasus Cluster, in Pegasus, magnitude 6.2, 34,900 light-years
11. NGC 2808, in Carina, magnitude 6.2, 32,800 light-years
12. NGC 6541 Caldwell 78, in Corona Australis, magnitude 6.3, 24,800 light-years
13. Messier 55 Summer Rose, in Sagittarius, magnitude 6.3, 17,400 light-years
14. NGC 362 Caldwell 104, in Tucana, magnitude 6.4, 28,800 light-years
15. Messier 92, in Hercules, magnitude 6.4, 27,700 light-years
16. Messier 62 Flickering Globular, in Ophiuchus, magnitude 6.5, 20,900 light-years
17. Messier 2, in Aquarius, magnitude 6.5, 38,100 light-years
18. Messier 10, in Ophiuchus, magnitude 6.6, 16,500 light-years
19. Messier 12 Gumball Cluster, in Ophiuchus, magnitude 6.7, 16,700 light-years
20. NGC 6388, in Scorpius, magnitude 6.7, 36,400 light-years

Because they gather toward the galactic center, the best are in the summer sky from the northern hemisphere, and highest from the southern hemisphere. How many rise at least 20° above the horizon from each latitude:

The nearest globular cluster is 6,030 light-years away, the farthest 480,000

Each dot is one cluster, on a scale where each step is ten times farther. Most lie within 50,000 light-years, in the inner halo around the galactic center; a few orbit far out in the halo, beyond the Magellanic Clouds.

William Herschel named them globular clusters in 1789

Abraham Ihle found the first, M22, in 1665. Charles Messier listed 29 in his catalog, though his small telescopes showed most as round nebulae. William Herschel's larger reflectors resolved them into stars, and in 1789 he called them globular clusters. Shapley's work in 1918 used them to find the center of the galaxy. They are among the oldest objects known, 10 to 13 billion years old, nearly as old as the universe.