Messier 107

Lore & Background

Messier 107 was discovered by Pierre Méchain in April 1782, then independently by William Herschel in 1793. Herschel's son, John, in his 1864 General Catalogue, described it as a 'globular cluster of stars, large, very rich, very much compressed, round, well resolved, clearly consisting of stars.' It was not until 1947 that Helen Sawyer Hogg added it and three other objects found by Méchain to the modern Catalogue, the latter having contributed several of the suggested observation objects which Messier had verified and added.

The cluster is close to the galactic plane and about 20,900 light-years from Earth and 9,800 ly (3,000 pc) from the Galactic Center. Its orbit is partly as far out as the galactic halo, as is between 9,200–12,400 ly (2,820–3,790 pc) from the Galactic Center, the lower figure, the 'perigalactic distance' sees it enter and leave the galactic bar. There are 22 known RR Lyrae variable stars in this cluster and a probable SX Phoenicis variable.

The cluster is to be found 2.5° south and slightly west of the star Zeta Ophiuchi.

Reader's Guide

Messier 107 is notable as the last object in the Messier Catalogue, a fact that underscores its late addition to the modern list. Its discovery history involves Pierre Méchain in April 1782 and an independent observation by William Herschel in 1793, with John Herschel later describing it in his 1864 General Catalogue. The cluster was not included in the modern Messier Catalogue until 1947, when Helen Sawyer Hogg added it along with three other Méchain objects. This cluster is a very loose globular cluster, located close to the galactic plane, and its orbit takes it partly into the galactic halo, with a perigalactic distance that brings it into the galactic bar. It contains 22 known RR Lyrae variable stars and a probable SX Phoenicis variable, making it of interest for studies of variable stars and galactic structure.

Did You Know?

• Messier 107 is the last object in the Messier Catalogue.
• It was discovered by Pierre Méchain in April 1782 and independently by William Herschel in 1793.
• It was added to the modern Messier Catalogue by Helen Sawyer Hogg in 1947.