Little Gem (NGC 6445) + Globular Cluster NGC 6440
Object Description
NGC 6445, also called Little Gem, is a bipolar planetary nebula and was discovered on May 28, 1786 by Wilhelm Herschel and cataloged as II 586. He described it as «pretty bright, small, of an irregular figure» [464] Distances range from 1.38 kpc [153] to 2.5 kpc [141]. Surrounding the nebula is a fine halo, whose filaments are visible far out on H-II images. [152]
| Designations | PN G008.0+03.9: NGC 6445, PK 8+03.1, ARO 67, He 2- 290, Sa 2-248, ESO 589-09, VV 118, VV' 260 |
| Right Ascension (J2000.0) | 17h 49m 16s |
| Declination (J2000.0) | -20° 00' 35" |
| Dimensions | 33." (optical), > 34." (radio) |
| Distance | 2.5 kpc |
| Radial Velocity | +16.2 km/s ± 0.5 km/s |
| Expansion Velocity | 38.0 km/s (O-III) |
| C-Star Designations | AG82 266, CSI -20 -17462, HD 161944 |
| C-Star Magnitude | 19.04 mag (B filter), 19.00 mag (V filter) |
| C-Star Spectral Type | Contin. |
| Discoverer | PICKERING 1882 |
Globular Cluster NGC 6440
NGC 6440 was discovered by Wilhelm Herschel in the same night and cataloged as I 150. He described it as «considerably bright, round, very gradually much brighter in the middle, about 1.5' diameter». [464] According to Simbad, it is moving towards us at 69 km/s. A distance measurement is not given. [145]
Auffindtipp
The open star cluster M 23 in the Sagittarius constellation leads directly to the planetary nebula NGC 6445. The southern globular star cluster NGC 6440 also serves as a further search aid. The sought-after planetary nebula is located directly west of a mag 7.5 star.
Visual Observation
350 mm aperture: A fine circle surrounds the planetary nebula NGC 6445. The cap-shaped bright spots in the north and south of the nebula are striking. The nebula smolders delicately in its inner region. It is advantageous to use a relatively high magnification, greater than 200x, so that the shape of the planetary nebula is also fully revealed. [192]