2MASS Picture of the Week Archive Captions

NGC 2024, also known as the Flame Nebula, is located at a distance of 400-500 pc and is part of the Orion Molecular Cloud Complex (Orion B). See Meyer & Lada (1999, The Orion Complex Revisited, ASP Conference Series, in press) and references therein for an overview of the region. To the south of the NGC 2024 region lies NGC 2023 (a well-studied photo-dissociation region) and the Horsehead Nebula (cf. David Malin's optical image). At near-infrared wavelengths, a dense stellar cluster is revealed in the dark lane separating the two halves of the flame. The age of the cluster is thought to be <1 Myr and the distribution of stellar masses appears to be consistent with that characterizing the solar neighborhood. Between 40-70% of the stars in this cluster are surrounded by circumstellar accretion disks, commonly associated with young stellar objects. Such disks may be sites of planet formation and could give rise to solar systems not unlike our own. Image mosaic by E. Kopan & R. Hurt (IPAC). Caption provided by M. Meyer (Steward Obs, U of A). Featured as an Astronomy Picture of the Day!

Find a "movie" of the optical versus 2MASS view of the Horsehead Nebula, near NGC 2024, here.


The Wolf-Rayet galaxy NGC 4214.



The globular star cluster Messier 13.



The bipolar planetary nebula NGC 2346.



The nearly edge-on Sb galaxy NGC 891, with its conspicuous dust lane, is often compared to the Milky Way Galaxy, due to its suspected resemblance. Thus, studying this galaxy provides insights on the nature of our own Galaxy. Imaging this galaxy in the near-IR allows us to look deeper through the extinction caused by the dust and also better map the light and mass distribution of the galaxy, since the light from spiral galaxies in the near-IR is dominated by lower-mass stars, which comprise most of a galaxy's visible mass. This galaxy was previously imaged in the near-IR by Aoki et al. (1991, PASJ, 43, 755) and Xilouris et al. (1998, A&A, 331, 894). Aoki et al. found that the patchy reddish color of the galaxy's disk is not only due to the dust lanes, but also to the light from late-type supergiants, with a z scale height of ~350 pc (assuming a distance of 9.8 kpc). From modelling of the optical and near-IR light, Xilouris et al. find an overall scale height for the stars of ~400 pc and a scale height for the dust of ~260 pc; the scale length for stars in the disk is 5.1 kpc, while for the dust, it is 7.5 kpc. Xilouris et al. conclude that if seen face-on, NGC 891 would be optically thin, and that from its estimated dust mass and extinction law, this galaxy is indeed very much like our own Milky Way.
Image mosaic by E. Kopan (IPAC).
































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