Messier 30

Lore & Background

Messier 30 was discovered by the French astronomer Charles Messier in 1764, who described it as a circular nebula without a star. In the New General Catalogue, compiled during the 1880s, it was described as a 'remarkable globular, bright, large, slightly oval.' It can be easily viewed with a pair of 10×50 binoculars, forming a patch of hazy light some 4 arcminutes wide that is slightly elongated along the east–west axis. With a larger instrument, individual stars can be resolved and the cluster will cover an angle of up to 12 arcminutes across, graduating into a compressed core about one arcminute wide that has further star density within.

The cluster has passed through a dynamic process called core collapse and now has a concentration of mass at its core of about a million times the Sun's mass per cubic parsec. This makes it one of the highest density regions in the Milky Way galaxy. Stars in such close proximity will experience a high rate of interactions that can create binary star systems, as well as a type of star called a blue straggler that is formed by mass transfer. A process of mass segregation may have caused the central region to gain a greater proportion of higher mass stars, creating a color gradient with increasing blueness toward the middle of the cluster.

Reader's Guide

Messier 30 is significant as a globular cluster that has undergone core collapse, resulting in an extraordinarily dense core—about a million solar masses per cubic parsec—making it one of the highest density regions in the Milky Way. Its retrograde orbit through the inner galactic halo suggests it was acquired from a satellite galaxy rather than forming within the Milky Way. The cluster's high stellar density leads to frequent interactions, producing binary star systems and blue straggler stars via mass transfer. Mass segregation may have concentrated higher-mass stars toward the center, creating a color gradient. It is longest observable (opposed to the Sun) in the first half of August. Its estimated age of roughly 12.9 billion years and mass of about 160,000 solar masses place it among the older and moderately massive globular clusters. The cluster is centered 27,100 light-years from Earth and is about 93 light-years across.

Did You Know?

• Messier 30 is also known as the Jellyfish Cluster.
• The cluster follows a retrograde orbit through the inner galactic halo, suggesting it was acquired from a satellite galaxy.
• Its core has a density of about a million times the Sun's mass per cubic parsec, one of the highest in the Milky Way.