Messier 43

Right Ascension	05 : 35.6 (h:m)
Declination	-05 : 16 (deg:m)
Distance	1.35 (kly)
Visual Brightness	9.0 (mag)
Apparent Dimension	20x15 (arc min)

Discovered before 1731 by Jean-Jacques Dortous de Mairan.

Messier 43 (M43, NGC 1982) is the companion of the Great Orion Nebula, M42. It is separated from the great nebula by an impressive, turbulent dark lane, and is lying 7 arcmin north of the Trapezium Cluster.

M43 was first reported by de Mairan in 1731 as a "brilliance surrounding a star" which he thought was "very similar to the atmosphere of our Sun, if it were dense enough and extensive enough to be visible in telescopes at a similar distance" (De Mairan 1733). Charles Messier included in his fine drawing of the Orion Nebula, and assigned it an extra catalog number, M43, on March 4, 1769. Moreover, William Herschel took it into his list with the number H III.1, although normally he careful avoided to assign his numbers to Messier Objects. In his 1811 paper, Herschel states to have observed it as early as March 4, 1774, and cataloged it on November 3, 1783. M43 shows up on the first deep photograph of the Orion Nebula, taken on March 14, 1882 by Henry Draper.

The diffuse nebula M43 surrounds the irregular young "nebula variable" NU Orionis (HD 37061, attn: "N" "U" Orionis, not "Nu Orionis", i.e. the variable star 2-letter designation, not the Greek letter). This star was determined to be of visual magnitude 6.5-7.6; its spectral type was once given as B IV, but was determined to be B 0.5 V by Schild and Chaffee (1971). Apparently, M43 is excited to shine by this star, which is quite cool for a central star of an H II region, and accounts for the comparatively low luminosity, or flux, of M43 at all wavelengths. Its distance roughly the same as that of the Great Nebula, about 1,350 light-years. At this distance, its diameter of 20 arc minutes corresponds to about 7.5 light-years.

M43 contains its own, separate small cluster of stars which have formed in this part of the Orion Nebula.

The dark features along its eastern border are well visible in telescopes starting at about 8 inch. The nebula itself is a fine view even in a 4-inch. Alister Ling, in his semi-recent review of observing the Orion nebula with filters, mentions the Comma shape of this nebula (Ling 1995).

Our image was obtained by David Malin with the 3.9-meter Anglo-Australian Telescope. More information on this image is available.

NGC Online data for M43

References

• De Mairan, 1733. Traite physique et historique de l'Aurore Boréale. Par M. de Mairan. Suite des Mémoires de l'Académie Royale des Sciences, Année M.DCCXXXI [Physical and historical treatise of the Aurora Borealis. By M. De Mairan. Series of the Memoirs of the Royal Academy of Sciences, for the year 1731]. Royal Printing Office, Paris, 1733. Second edition, 1754. A translation of his descriptions of nebulae, on pages 259-263 of this work, is available online.
• Alister Ling, 1995. Astronomy (December 1995)
• Schild and Chaffee, 1971. Energy Distributions and Spectra of Orion B Stars. Astrophysical Journal, Vol. 169, No. 3, pp. 529-536 (Nov 1971) [ADS: 1971ApJ...169..529S]

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Hartmut Frommert
Christine Kronberg
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Last Modification: October 8, 2018