Little Gem (NGC 6445) + Globular Cluster NGC 6440

Object Description

NGC 6445
NGC 6445: Section of PanSTARRS1 DR1 color [147]

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]

«Strasbourg-ESO Catalogue of Galactic Planetary Nebulae» Acker et al., 1992 [141]
DesignationsPN 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 DesignationsAG82 266, CSI -20 -17462, HD 161944
C-Star Magnitude19.04 mag (B filter), 19.00 mag (V filter)
C-Star Spectral TypeContin.
DiscovererPICKERING 1882

Globular Cluster NGC 6440

NGC 6440
NGC 6440: Section of PanSTARRS1 DR1 color [147]

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]

«Revised New General Catalogue and Index Catalogue» Dr. Wolfgang Steinicke, 2021 [277]
DesignationNGC 6440
TypeGCL (V)
Right Ascension17h 48m 52.6s
Declination-20° 21' 32"
Diameter4.40 arcmin
Visual magnitude9.3 mag
Dreyer DescriptionpB, pL, R, bM
IdentificationGCL 77, ESO 589-SC8

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.

Chart NGC 6440, NGC 6445
Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

Visual Observation

NGC 6445
NGC 6445: Pencil drawing; 14" PWO-Dobson f/4.6, TV-Nagler-Zoom 6 mm, 267x, 0.19°; Honegg 1460 m; © 30. 7. 2003, 00:15 Eduard von Bergen

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]

14" PWO-Dobson, F:4.6 / TV-Nagler-Zoom 6mm, 266x, 0.19°,
Eduard von Bergen

References

141Strasbourg-ESO Catalogue of Galactic Planetary Nebulae; A. Acker, F. Ochsenbein, B. Stenholm, R. Tylenda, J. Marcout, C. Schohn; European Southern Observatory; ISBN 3-923524-41-2 (1992); cdsarc.unistra.fr/viz-bin/cat/V/84 (2021-02-18)
145SIMBAD astronomical database; simbad.u-strasbg.fr/simbad
147Aladin Lite; aladin.u-strasbg.fr/AladinLite (2020-12-23)
149SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
152«Extended Structures of Planetary Nebulae Detected in H2 Emission»; Xuan Fang, Yong Zhang, Sun Kwok, Chih-Hao Hsia, Wayne Chau, Gerardo Ramos-Larios, Martin A. Guerrero; arXiv:1804.08840; DOI:10.3847/1538-4357/aac01e
153«The Magellanic Cloud Calibration of the Galactic Planetary Nebula Distance Scale» Letizia Stanghellini, Richard A. Shaw, and Eva Villaver; The Astrophysical Journal, Volume 689, Number 1, 2008; DOI:10.1086/592395
160The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
192Deep-Sky Guide; fernrohr.ch/1d_deep-sky-guide.html (2020-12-25)
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; klima-luft.de/steinicke (2021-02-17)
464«Catalogue of a second thousand of new nebulae and clusters of stars; with a few introductory remarks on the construction of the heavens» William Herschel, Philosophical Transactions of the Royal Society of London, 1 January 1789; DOI:10.1098/rstl.1789.0021