IC 447, Dreyer's Nebula

IC 446, IC 447, NGC 2245, NGC 2247
IC 446, IC 447, NGC 2245, NGC 2247: Molecular Cloud in Monoceros. Section from DSS [147]

History

On January 18, 1784 William Herschel noticed a «pretty bright milky [nebula] like a star with an electrical brush» while this part of the sky was drifting through the field of view of his 18.7 inch reflecting telescope. [463] He most likely referred to an electrical brush discharge or a Saint Elmo's fire — as it was about half a century before the invention of electrical motors. The nebula was cataloged as IV 3 which later became NGC 2245 in Dreyer's New General Catalogue. [196, 313]

The discovery of NGC 2247 is credited to the Irish astronomer R. J. Mitchell, an assistent of William Parsons, the 3rd Earl of Rosse. He discovered the nebula on February 14, 1857 using the giant 72 inch reflector «Leviathan» at Birr Castle. Dreyer gives the following description: «Nebulous star in extremely faint, extremely large nebulosity, north following IV 3 [NGC 2245]» [196, 313]

The American astronomer Edward Emerson Barnard exposed photographic plates of this region on October 11, 1888 using a 12 inch refractor and again on January 21 and 24, 1894 using the 6 inch Willard lens. He published his discovery in Astronomy and Astro-Physics on March 1894 describing: «I found a very large, weak, diffused nebulosity some half a degree south of the nebula NGC 2245. This was mixed up with several considerable stars. I also found a 10 mag nebulous star about half a degree north preceeding 2245.» [472] These discoveries were added 1895 by Dreyer as IC 446 and IC 447 by his Index Catalogue [314] For some reasons both nebula were also added 1910 in Dreyer's Second Index Catalogue as IC 2167 (= IC 446) and IC 2169 (= IC 447) with slightly different coordinates. [277, 315] In 1919 Barnard published a catalogue of 182 dark nebulae from which B 37, B 38 and B 39 are located within that area. [239]

The Canadian astronomer Sidney van den Bergh identified the reflection nebulae vdB 76, vdB 77, vdB 78 and vdB 79 on the photo plates of the Palomar Observatory Sky Survey (POSS) in his 1966 Study of Reflection Nebulae. [255]

IC 447 is also sometimes known as Dreyer's Nebula, although the reason for this naming is unclear. He published his famous New General Catalogue in the same year as Barnard discovered that nebula though.

Physical Properties

All these discovered bright and nebulae belong to a large molecular cloud, the Monoceros R1 (Mon R1) Complex which mean distance from Earth is around 716 pc. It is an active starforming region and hosts many young stars and Herbig-Haro objects, bright patches of nebulosity associated with newborn stars. [474, 475]

«Revised New General Catalogue and Index Catalogue», «Historically Corrected New General Catalogue», Dr. Wolfgang Steinicke, 2021 [277]
NameRADecTypeBmagVmagDimDreyer DescriptionIdentification
NGC 2245 06 32 41.2+10 09 24RN5.00 × 4.0pL, com, mbN sf alm *, * 7·8 nfLBN 904
NGC 2247 06 33 05.1+10 19 18RN6.00 × 6.0Neb * in eF, eL neby, nf IV 3LBN 901
IC 446 06 31 06.0+10 27 35RN+*5.00 × 4.0Neb * 10mIC 2167, LBN 898, CED 77
IC 447 06 31 04.0+09 52 00RN25.00 × 20.0vF, eeL, difIC 2169, LBN 903
IC 2167 06 31 06.0+10 27 35RN+*5.00 × 4.0* 9.5 in F, L nebIC 446, LBN 898, CED 77
IC 2169 06 31 04.0+09 52 00RN25.00 × 20.0F, L, dif, sev st 9-10 invIC 447, LBN 903

Finder Chart

The nebula complex is located in the constellation Monoceros, approximately 2.5° west of 15 Monocerotis. The best season for observation is from October until March.

Chart IC 447
Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

References

147Aladin Lite; aladin.u-strasbg.fr/AladinLite (2020-12-23)
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)
239«On the dark markings of the sky, with a catalogue of 182 such objects» Barnard, E. E.; Astrophysical Journal, 49, 1-24 (1919); DOI:10.1086/142439; Bibcode:1919ApJ....49....1B
255«A study of reflection nebulae» van den Bergh, S.; Astronomical Journal, Vol. 71, p. 990-998 (1966); DOI:10.1086/109995
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; klima-luft.de/steinicke (2021-02-17)
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
314«Index Catalogue of Nebulæ found in the years 1888 to 1894, with Notes and Corrections to the New General Catalogue» Dreyer, J. L. E.; Memoirs of the Royal Astronomical Society, Vol. 51, p.185; 1895; Bibcode:1895MmRAS..51..185D
315«Second Index Catalogue of Nebulae and Clusters of Stars; containing objects found in the years 1895 to 1907, with Notes and Corrections to the New General Catalogue and to the Index Catalogue for 1888–94» Dreyer, J. L. E. (1910); Memoirs of the Royal Astronomical Society. 59: 105–198; Bibcode:1910MmRAS..59..105D
463«Catalogue of one thousand new nebulae and clusters of stars» William Herschel, Philosophical Transactions of the Royal Society of London, 1 January 1786; DOI:10.1098/rstl.1786.0027
472«Photographic Nebulosities and Star Clusters Connected with the Milky Way» E. E. Barnard, Astronomy and Astro-Physics, Vol. XIII, No. 3, March 1894, pages 177-183; books.google.ch/books?id=AQHD6xPQYe4C&pg=PA177 (2022-01-19)
474«Star-forming Sites IC 446 and IC 447: An Outcome of End-dominated Collapse of Monoceros R1 Filament» N. K. Bhadari, L. K. Dewangan, L. E. Pirogov, and D. K. Ojha; The Astrophysical Journal, Volume 899, Number 2, 2020; DOI:10.3847/1538-4357/aba2c6
475«New Herbig–Haro objects and outflows in the Mon R1 association» T A Movsessian, T Yu Magakian, S N Dodonov; Monthly Notices of the Royal Astronomical Society, Volume 500, Issue 2, January 2021, Pages 2440–2450; DOI:10.1093/mnras/staa3302