Messier 26

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Messier 26, also known as NGC 6694, is an open cluster of stars in the southern constellation of Scutum. It was discovered by Charles Messier in 1764.Template:Efn This 8th magnitude cluster is a challenge to find in ideal skies with typical binoculars, where it can be, with any modern minimum Template:Convert aperture device. It is south-southwest of the open cluster Messier 11 and is Template:Val across.<ref name=Thompson2007/> About 25 stars are visible in a telescope with a Template:Convert aperture.<ref name=Burnham1978/>

M26 spans a linear size of 22<ref name=Kharchenko2009/> light years across with a tidal radius of Template:Convert,<ref name=Piskunov2008/> and is at a distance of 5,160<ref name=kharchenko2005/> light years from the Earth. The brightest star is of magnitude 11<ref name=Burnham1978/> and the age of this cluster has been calculated to be 85.3<ref name=Wu2009/> million years. It includes one known spectroscopic binary system.<ref name=Mermilliod2007/>

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".<ref name=Cuffey1940/> In 2015, Michael Merrifield of the University of Nottingham said that there is, as yet, no clear explanation for the phenomenon.<ref name=Merrifield2015/>