Barnards Galaxy (NGC 6822)

NGC 6822
NGC 6822: Image taken with the 2.2 meter MPG/ESO telescope of the ESO Observatory on La Silla in Chile [275]

History

This irregular dwarf galaxy was discovered on 17 August 1884 by American astronomer Edward Emerson Barnard using the 6 inch Cook refractor at Vanderbilt Observatory in Nashville, Tennessee. Barnard's galaxy was recorded as NGC 6822 by Dreyer in his «New General Catalogue of Nebulae and Clusters of Stars», published in 1888. Due to a series of confusions with later observations by Herbert Howe and Max Wolf, who used larger telescopes and did not see the galaxy as a whole, the same object was included in Dreyer's later «Index Catalogue» with the designations IC 1380 for a single H-II region (Hubble-X) and IC 4895 for the whole group of H-II regions in the galaxy.

Hubble-X (IC 1308)
Hubble-X (IC 1308): Image taken with Hubble Space Telescope. © ESA/Hubble & NASA [276]

Physical Properties

Like our Milky Way and the Andromeda galaxy, NGC 6822 belongs to the Local Group. At a distance of about 1.6 million light-years, it is closer than the Andromeda galaxy, but measures just 8000 light-years in diameter. Numerous H-II regions heated by young hot stars are evidence of active star formation. The stellar population is comparable to that of the Magellanic Clouds. The image in Fig. 1 was taken with four different filters (B, V, R, and Hα) and measures 34' x 35'. [4, 196, 274, 275]

Fig. 2 shows a Hubble Space Telescope image of the H-II region of the active star-forming region Hubble-X (IC 1308). This glowing cloud of gas is about 110 light-years across and hosts several thousand newly formed stars at its center. Hubble-X is many times larger and brighter than the Orion Nebula, which is about the size of the small, poorly resolved nebula below. The designation Hubble-X refers to Edwin's 1923 study of the H-II regions in this dwarf galaxy and is a Roman ten. [276]

Revised+Historic NGC/IC, Version 22/9, © Dr. Wolfgang Steinicke [277]
NameRADecTypebMagvMagDimDreyer DescriptionIdentification, Remarks
NGC 682219 44 56.6-14 48 23Gx (IBm)9.38.715.4 × 14.2vF, L, E, difIC 4895, MCG -2-50-6, DDO 209, IRAS 19421-1455, Barnard's galaxy
IC 130819 45 05.2-14 43 17GxyP14.00.6eF, eS, lE, gbM, 6822 p 12sLBN 83, part of N 6822
IC 489519 44 56.6-14 48 23dup9.38.715.4 × 14.2Group of neb, 25' diamNGC 6822, MCG -2-50-6, DDO 209, IRAS 19421-1455, Barnard's galaxy

Finder Chart

Neighboring dwarf galaxy NGC 6822 is in the constellation Sagittarius, actually closer to Capricornus. It is slightly west of midpoint between α12 Capricorni and υ Sagittarii. It is best seen from June to August. The apparent size of the dwarf galaxy and the low surface brightness assume a dark southern sky.

Chart Barnards Galaxy (NGC 6822)
Barnards Galaxy (NGC 6822) in constellation Sagittarius. Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

More Objects Nearby (±15°)

References

4«Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System» by Robert Burnham; Dover Publications, Inc.; Voume I: ISBN 0-486-23567-X; Volume II: ISBN 0-486-23568-8; Volume III: ISBN 0-486-23673-0
149SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
160The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
196Celestial Atlas by Curtney Seligman; cseligman.com/text/atlas.htm (2020-12-28)
274NGC 6822 von Wolfgang Steinicke; klima-luft.de/steinicke/Artikel/NGC6822.pdf (2021-02-17)
275Barnard's Galaxy; eso.org/public/images/eso0938a (2021-02-17)
276Hubble X: A glowing gas cloud in the star-forming region of galaxy NGC 6822; hubblesite.org/contents/media/images/2001/01/1012-Image.html (2021-02-17)
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; klima-luft.de/steinicke (2021-02-17)