Heart Nebula (IC 1805)

NGC 896, IC 1795, IC 1805
NGC 896, IC 1795, IC 1805: Heart Nebula in Cassiopeia; Celestron RASA 11" f/2.22; ZWO ASI6200 Pro; Tentlingen; © 2020 Peter Kocher [33]
NGC 896, IC 1795, IC 1805
NGC 896, IC 1795, IC 1805: Heart Nebula in Cassiopeia; TS Triplet APO 90, Reducer Photoline 0.79 (490mm / f5.44), SBIG ST-8300; 28L x 300 sec 1×1, 218R, 28G, 24B 2×2 300 sec; Bernese Highlands; © 2018 Bernhard Blank, Dragan Vogel [32]
IC 1805
IC 1805: Emission nebula in Cassiopeia; Takahashi FSQ-106 EDX f=530 mm; Moravian G2-8300; Vixen New Atlux; 16 x 20 Min. = 5 h 20 min. (-20°); Gurnigel; © 18. 10. 2014 Jonas Schenker [34]

History

On 3 November 1787, the German-British astronomer William Herschel discovered a «very faint nebula» which he cataloged as WH III 695 and described as: «extremely faint, pretty large, of irregular figure.» [464] John L. E. Dreyer included it in 1888 as NGC 896 in his «New General Catalogue of Nebulae and Clusters of Stars». [313]

In 1890 the American astronomer Edward Barnard photographed the same section of the sky and discovered a «foggy spot» a little northeast at the location noted for NGC 896, which John L. E. Dreyer unwittingly included in his second «Index Catalogue» as IC 1795 as a double entry for NGC 896. Presumably Herschel only saw the brightest western part of IC 1795. About one degree southeast of this nebula Barnard discovered another large nebula in which an open star cluster was embedded. This then became IC 1805. [196]

In 1915 British astronomer Philibert Jacques Melotte published a catalogue of Star Clusters shown on Franklin-Adams Chart Plates, a photographic star atlas prepared by John Franklin-Adams and published in 1914. The catalogue contains 245 clusters and IC 1805 is listed there as number 15, hence the designation Mel 15 (or Melotte 15). He gave a diameter of 15 arcminutes and noted: «A very loose cluster. Somewhat similar to NGC 1027, but stars not so numerous and generally brighter.» [158]

Heart- and Soul Nebula
Heart- and Soul Nebula: FOV 6° Section of the DSS2 [147]

In 1931 Swedish astronomer Per Collinder listed IC 1805 as cluster nr. 26 (Collinder 26) [455]

In 1946 Swedish astronomer Sven Cederblad published his «Studies of bright diffuse galactic nebulae with special regard to their spatial distribution» and included the nebulosity IC 1795 as Cederblad 6 and noted: «The nebula apparently consists of three parts: 6a = +61 411 with a fan-shaped appendix; 6b = A thirteenth mag. star with ditto; 6c = General background veil.» The nebula IC 1805 is there listed as Cederblad 7 and noted: «R. Nebulous cluster containing the BD stars: [...]. The spectra of these stars are stated to be "perhaps B0". There is a conspicuous condensation at [BD] +60 507.» [130]

In 1959 the American astronomer Stewart Sharpless included the nebula around cluster IC 1805 as Sh 2-190 in his famous «Catalogue of H-II Regions». His catalogue covers 313 H-II regions identified on the photo plates of the «Palomar Observatory Sky Survey» down to a declination of -27°. [310]

Physical Properties

All objects (NGC 896, IC 1795 and IC 1805) are connected to one another, large H-II area and form the «Heart Nebula», which is formed by the young O and B stars in the star cluster in IC 1805 (Collinder 26, Melotte 15) can be excited to glow. On Simbad a distance of 4.1 kpc (13'400 light years) is found for IC 1795. For IC 1805 one finds distances of 1.7 kpc to 6.1 kpc (around 5500 to 20'000 light years). The real distance is probably somewhere in between. [145]

Revised+Historic NGC/IC Version 22/9, © 2022 Dr. Wolfgang Steinicke [277]
Name RA Dec Type vMag Dim MD Dreyer Description Identification, Remarks
NGC 896 02 25 27.8 +62 01 10 EN 10 × 10 2.300 eF, pL, iF WH III 695; GC 531; IC 1795; LBN 645; CED 6; SG 1.04; Min 2-57; narrrow dark lane n-s, SNR ?
NGC 1027 02 42 36.0 +61 35 42 OCL (III2p) 6.7 15 0.772 Cl, L, sc st, one 10 m WH VIII 66; GC 578; IC 1824; OCL 357
IC 1795 02 25 27.8 +62 01 10 dup 10 × 10 2.300 Patch of neby NGC 896; LBN 645; CED 6; SG 1.04; Min 2-57; narrrow dark lane n-s, SNR ?
IC 1805 02 32 48.0 +61 27 42 OCL (III3pn) 6.5 20 1.886 Cl, co, eL neby extends f OCL 352; Mel 15; LBN 654
IC 1824 02 42 36.0 +61 35 42 dup 6.7 15 0.772 Cl, st F, perh. F neby p extends to it NGC 1027; OCL 357

Finder Chart

The Heart Nebula is located in the constellation Cassiopeia. In Central Europe it is circumpolar. The best time to observe, however, is July to January, when the constellation is highest at night. About 2.5 degrees further east is another nebula, the «Soul Nebula» (Sh 2-199 with cluster IC 1848). Both nebulae are often referred to together as the «Heart and Soul Nebula».

Finder Chart Heart Nebula (IC 1805)
Heart Nebula (IC 1805) in constellation Cassiopeia. Charts created using SkySafari 6 Pro and STScI Digitized Sky Survey. Limiting magnitudes: Constellation chart ~6.5 mag, DSS2 close-ups ~20 mag. [149, 160]

Objects Within a Radius of 10°

References

  • [32] Astrofotografie by Radek, Bernie and Dragan; sternwarte.ch
  • [33] Sternwarte Tentlingen MPC A16, Peter Kocher; astropeter.ch
  • [34] Astrofotographie von Jonas Schenker; extrasolar.ch
  • [130] «Studies of bright diffuse galactic nebulae with special regard to their spatial distribution.» Cederblad, S.; Lund Medd. Astron. Obs. Ser. II, Vol. 119, p. 1-166 (1946); Bibcode:1946MeLuS.119....1C
  • [145] SIMBAD astronomical database; simbad.u-strasbg.fr/simbad
  • [147] Aladin Lite; aladin.unistra.fr/AladinLite
  • [149] SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
  • [158] «A Catalogue of Star Clusters shown on Franklin-Adams Chart Plates» Melotte, P. J.; Memoirs of the Royal Astronomical Society, Vol. 60, p.175, 1915; Bibcode:1915MmRAS..60..175M
  • [160] The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
  • [196] Celestial Atlas by Curtney Seligman; cseligman.com/text/atlas.htm (2020-12-28)
  • [277] «Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; klima-luft.de/steinicke (2021-02-17)
  • [310] «A Catalogue of H II Regions» Stewart Sharpless, US Naval Observatory, 1959; DOI:10.1086/190049; Bibcode:1959ApJS....4..257S
  • [313] «A New General Catalogue of Nebulae and Clusters of Stars, being the Catalogue of the late Sir John F.W. Herschel, Bart., revised, corrected, and enlarged» Dreyer, J. L. E. (1888); Memoirs of the Royal Astronomical Society. 49: 1–237; Bibcode:1888MmRAS..49....1D
  • [455] «On Structural Properties of Open Galactic Clusters and their Spatial Distribution. Catalog of Open Galactic Clusters.» Collinder, Per; Annals of the Observatory of Lund, vol. 2, pp.B1-B46, 1931; Bibcode:1931AnLun...2....1C
  • [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