Messier 26

Lore & Background

Messier 26 was discovered by Charles Messier in 1764. It is an 8th magnitude open cluster in the southern constellation of Scutum, located south-southwest of the open cluster Messier 11. The cluster spans a linear size of 22 light years across with a tidal radius of 25 light-years, and is at a distance of 5,160 light years from Earth. Its brightest star is of magnitude 11, and the cluster's age has been calculated to be 85.3 million years. It includes one known spectroscopic binary system.

An interesting feature of M26 is a region of low star density near the nucleus. A hypothesis was that it was caused by an obscuring cloud of interstellar matter between us and the cluster, but a paper by James Cuffey suggested that this is not possible and that it really is a 'shell of low stellar space density.' In 2015, Michael Merrifield of the University of Nottingham said that there is, as yet, no clear explanation for the phenomenon.

Reader's Guide

Messier 26 is notable for its challenging visibility and a peculiar structural feature. The cluster is difficult to spot with typical binoculars even under ideal skies, requiring at least a 3-inch (76 mm) aperture device. In a telescope with a 150–200 mm (6–8 in) aperture, about 25 stars are visible. Its most intriguing characteristic is a region of low star density near its nucleus, which has prompted scientific debate. A hypothesis that this void is caused by an obscuring cloud of interstellar matter was contradicted by a paper from James Cuffey, who argued it is a genuine shell of low stellar space density. As of 2015, Michael Merrifield of the University of Nottingham stated that no clear explanation for the phenomenon exists. This unresolved mystery makes M26 a subject of ongoing interest in the study of open clusters.

Did You Know?

• The cluster has a region of low star density near its nucleus, with no clear explanation as of 2015.
• The cluster's age is calculated to be 85.3 million years.