Planetary nebula in the constellation Sagittarius
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]
^ a b c d "NGC 6445" . SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 28 December 2018 .
^ Stanghellini, Letizia; Shaw, Richard A.; Villaver, Eva (10 December 2008). "The Magellanic Cloud Calibration of the Galactic Planetary Nebula Distance Scale" . The Astrophysical Journal . 689 (1): 194–202. arXiv :0807.1129 . Bibcode :2008ApJ...689..194S . doi :10.1086/592395 . S2CID 119257242 .
^ "Revised NGC Data for NGC 6445" . spider.seds.org .
^ Michael E. Bakich (June 11, 2015). "Open cluster IC 4665, the Box Nebula (NGC 6445), and globular cluster" . Astronomy.com . Retrieved 27 December 2018 .
^ "Best of AOP: NGC 6445: The Box Nebula" . www.noao.edu . National Optical Astronomy Observatory . Archived from the original on 28 December 2018. Retrieved 27 December 2018 .
^ Seligman, Courtney. "NGC 6445 (= P-K 008+03.1 = "PGC 3517785"), the Little Gem Nebula" . Celestial Atlas . Retrieved 19 November 2018 .
^ Kimeswenger, S.; Barría, D. (14 August 2018). "Planetary nebula distances in Gaia DR2" . Astronomy & Astrophysics . 616 : L2. arXiv :1807.06368 . Bibcode :2018A&A...616L...2K . doi :10.1051/0004-6361/201833647 . S2CID 58893001 .