NGC 6717, Palomar 9

RA:

18:55:06.04

Dec:

-22:42:05.3

Distance from Sun:

23.1 kly

Distance from Galactic Center:

7.8 kly

Apparent Diameter:

9.9 arc min

Brightness:

9.28 mag vis

Radial Velocity:

+22.8 +/- 3.4 km/s

Diameter:

ly

Abs. Mag:

-5.66 Mag vis

William Herschel discovered this cluster and cataloged it as H III.143. He described it as a very faint round nebula and apparently thought it was a cluster with nebulosity. It was first recognized as globular cluster by Per Collinder in 1931. When compiling his catalog of newly discovered globular clusters, George Abell (1955) included this object, apparently unaware of its identity, as it was not previously classified as a globular cluster. Its identification with NGC 6717 was probably done in 1958 by Alter.

It is of historical interest that a stellar lump in this cluster was cataloged separately as IC 4802 on the grounds of its observation by Bigourdan around 1900 (Bigourdan 434).

The image in this page is a photograph by Martin Germano with his 14.5" f/5 Newtonian stopped to f/6 (12"). It was exposed 45 minutes on hypered Tech Pan 2415. The bright star in this image is 35 Sgr at about 5th magnitude.

Links:

• The Palomar Globulars, by Barbara Wilson, Doug Snyder and Jim Shields
• Catalog of Variable Stars in NGC 6717 (Pal 9) (Christine Clement)

• George O. Abell, 1955. Globular Clusters and Planetary Nebulae Discovered on the National Geographic Society-Palomar Observatory Sky Survey. Publications of the Astronomical Society of the Pacific, Vol. 67, No. 397, p. 258 (August 1955) [ADS: 1955PASP...67..258A]