Messier 9 or M9 (also designated NGC 6333) is a globular cluster in the constellation Ophiuchus. It has an apparent visual magnitude of 7.7 and its angular diameter is 9.3 arc-minutes. M9 lies at an estimated distance of 26,700 light years. The Equinox 2000 coordinates are RA= 17h 19.2m, Dec= -18° 31´ which makes M9 best seen during the summer. The Messier Summer Star Chart shows the position of all Messier objects visible during that season.
The image above shows the uncropped view of M9 through the Takahashi E-180 Astrograph (North is up). A 3x enlargement of this image appears to the right.
This globular cluster was discovered by Messier in 1764. According to Recio-Blanco et al.(2005), the distance of M9 is 46,090 light years and its diameter is 150 light years. This would make its physical diameter about 90 light years and its distance from the Galactic Center about 5,500 light years. However, other references (e.g., Jones (1991)) place the cluster at half that distance or 25,800 light years. The estimated mass of M9 is 300,000 solar masses and it contains 16 variable stars.
Messier's Description of M9
May 28, 1764
`Nebula, without star, in the right leg of Ophiuchus; it is round and its light is faint. Reviewed on March 22, 1781. (Diam. 3')'
- Object: M9
- Other Names: NGC 6333
- Object Type: globular cluster
- Object Data: Apparent Magnitude = 7.7, Angular Size = 9.3 arc-minutes
- Object Position (Equinox 2000): RA= 17h 19.2m, Dec= -18° 31´, Constellation = Ophiuchus
- Date/Time: 2011 Apr 11 at 11:13 UTC
- Location: Bifrost Astronomical Observatory, Portal, AZ
- Mount: Astro-Physics 1200GTO
- Telescope: Takahashi Epsilon 180 Hyperbolic Astrograph
- Camera: Canon EOS 550D (Rebel T2i) (modified with a Baader UV/IR filter)
- Field of View: 1.70° x 2.56° at 1.7 arc-sec/pixel (web version: 10.0 arc-sec/pixel)
- Exposure: 2 x 300s, f/2.8, ISO 800
- File Name: M9-01w.jpg
- Processing (Adobe Camera Raw): Graduated Filter, Vignetting Correction, Noise Reduction, White Balance, Curves
- Processing (Photoshop CS5): Average Images, Curves, Noise Reduction
- Original Image Size: 3454 × 5179 pixels (17.9 MP); 11.5" x 17.3" @ 300 dpi
- Rights: Copyright 2011 by Fred Espenak. All Rights Reserved. See: Image Licensing.