imported>Ro Thorpe |
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| '''NGC 1976'''<ref>Hirshfeld, Alan, and Roger W. Sinnott, eds., Sky Catalogue 2000.0, Vol.2, Cambridge, Massachusetts: Sky Publishing Corp. and Cambridge University Press, 1985. (3098,238)</ref><ref>NGC 2000.0, The Complete New General Catalogue and Index Catalogue of Nebulae and Star Clusters by J.L.E. Dreyer Sinnott, R.W. (edited by) <Sky Publishing Corporation and Cambridge University Press (1988)></ref>, which is also called [[M 42]], [[Orion Nebula]] or [[Great Nebula in Orion]], is an [[emission nebula]] located in the constellation [[Orion]]. | | '''NGC 1976''', also known as '''M 42''', the '''Orion Nebula''' or the '''Great Nebula in Orion''', is an [[emission nebula]] located in the constellation [[Orion]]. |
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| {{Infobox NGCobject | | {{Infobox NGCobject |
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| | type = [[Emission nebula]] | | | type = [[Emission nebula]] |
| | epoch = 2000.0 | | | epoch = 2000.0 |
| | ra = 05<sup>h</sup>35.4<sup>m</sup> | | | ra = |
| | de = -05<sup>o</sup>27<sup>'</sup> | | | de = |
| | app_size = 66.0 | | | app_size = |
| | app_mag = 4.0 | | | app_mag = |
| | distance_ly = | | | distance_ly = |
| | const = Orion | | | const = Orion |
| | radius_ly = | | | radius_ly = |
| | redshift = | | | redshift = |
| | other = [[Great Nebula in Orion]], [[M 42]] | | | other = Great Nebula in Orion, M 42, Orion Nebula |
| | source = Hirshfeld, Alan, and Roger W. Sinnott, eds., Sky Catalogue 2000.0, Vol.2, Cambridge, Massachusetts: Sky Publishing Corp. and Cambridge University Press, 1985. (3098,238) | | | source = |
| | org_source = NGC 2000.0, The Complete New General Catalogue and Index Catalogue of Nebulae and Star Clusters by J.L.E. Dreyer Sinnott, R.W. (edited by) <Sky Publishing Corporation and Cambridge University Press (1988)> | | | org_source = |
| }} | | }} |
| === Appearance === | | === Appearance === |
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| === Location === | | === Location === |
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| It lies to the south of [[Orion]]'s Belt, visible to the naked eye. It includes [[The Trapezium]], the quadruple star [[Theta Orionis]] (θ Orionis). It is the closest region of star formation to Earth. | | It lies to the south of [[Orion]]'s Belt, visible to the naked eye. It includes the [[Trapezium]], the quadruple star [[Theta Orionis]] (θ Orionis). It is the closest region of star formation to Earth. |
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| === Scientific research === | | === Scientific research === |
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| * Our study<ref> Dupac et al., Cold Dust Condensations in Orion M42, ApJ, 553, 604 </ref>shows a large distribution of temperatures and spectral indexes in and around a dense and active molecular complex, the M42 Orion Nebula. The temperature varies from 12 to 70 K, and the spectral index from 1.1 to 2.2. The finding of two new cold clouds (clouds 3 and 4) confirms that the existence of cold condensations in such regions is not unusual. However, the extended cold clumps are located in the outskirts of the active star forming area. They may be the sites for future star formation.<br> The statistical analysis of the temperature and spectral index spatial distribution shows an evidence for an inverse correlation between these two parameters. This effect is not well explained yet, especially in the submillimeter spectral range for cold grains (<20 K). It has been shown to occur in the laboratory for warm grains by Mennella et al. (1998) and for cold grains in the millimeter by Agladze et al. (1996).<br>We estimated the column densities and masses of the observed regions by simply modeling the thermal emission of the grains from Désert et al. (1990) or Ossenkopf & Henning (1994). There is a good agreement between the 13CO column densities and those derived from our submillimeter measurement. This demonstrates the robustness of dust opacity values in the grain models. The submillimeter-wide band spectro-imaging is thus a natural way to derive masses in the interstellar medium.<br> Finally, we see a trend that the closer to the complex the cold clouds are, the more unstable they are. The history of star formation around OMC-1 shows that there have already been three to four successive bursts of star formation in this region with the embedded cluster responsible for the BN/KL object being the latest. The clouds that we observe close to the active region may thus be the seeds of the next generation of stars. This is, of course, quite speculative and should be sustained by more observations, particularly of the possible embedded protostars.
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| === References === | | === References === |
| {{reflist}} | | {{reflist}}[[Category:Suggestion Bot Tag]] |
