NGC 6445
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| Emission nebula | |
|---|---|
| Planetary nebula | |
 NGC 6445 by PanSTARRS | |
| Observation data: J2000 epoch | |
| Right ascension | 17h 49m 15s[1] |
| Declination | −20° 00′ 35″ [1] |
| Distance | 4.5 Kly (1.38 Kpc)[2] ly |
| Apparent magnitude (V) | 11.2[3] |
| Apparent dimensions (V) | 0.53′ × 0.53′[1] |
| Constellation | Sagittarius |
| Designations | PK 008+03 1, Little Gem Nebula,[1] Box Nebula[4][5] |
NGC 6445, also known as the Little Gem Nebula or Box Nebula, is a planetary nebula in the constellation Sagittarius. It was discovered by William Herschel on May 28, 1786.[6] The distance of NGC 6445 is estimated to be slightly more than 1,000 parsecs based on the parallax measured by Gaia, which was measured at 0.9740±0.3151 mas.[7]
NGC 6445 has been classified as a bipolar planetary nebula.[8][9] Its He/H and N/O abundance ratios are consistent with the Type I definition.[10] In optical images, NGC 6445 features a bright, central ring-shaped morphology and open bipolar lobes;[11] the outer envelope emission of NGC 6445 is [NII]-dominant.[12] Wide-field optical images obtained by the Nordic Optical Telescope (NOT) Andalucía Faint Object Spectrograph and Camera (ALFOSC) show that NGC 6445 has an irregularly shaped central region with a size of ~40"×50", where the [OIII] emission dominates, while the [NII] emission is much more extended and defines an overall bipolar morphology.[13] At distance, NGC 6445 is 4 light years across and is among the largest known.[14]
