NGC 1976

NGC 1976, also known as M 42, Orion Nebula or Great Nebula in Orion, is an emission nebula located in the constellation Orion.

NGC 1976
Observation data: 2000.0 epoch
Constellation	Orion
Right ascension	05h35.4m
Declination	-05o27'
Type	Emission nebula
Apparent dimensions	66.0
Apparent magnitude	4.0
Other designations	Great Nebula in Orion, M 42, Orion Nebula

Location

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.

Scientific research

• Our studyshows 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.
  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).
  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.
  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.