Messier 26, also known as NGC 6694, is an open cluster of stars in the southern constellation of Scutum.

[a] This 8th magnitude cluster is a challenge to find in ideal skies with typical binoculars, where it can be, with any modern minimum 3-inch (76 mm) aperture device.

The brightest star is of magnitude 11[6] and the age of this cluster has been calculated to be 85.3[1] million years.

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".

[9] In 2015, Michael Merrifield of the University of Nottingham said that there is, as yet, no clear explanation for the phenomenon.