2MASS Picture of the Week Archive Captions

The high-mass star formation region K3-50. The red nebular region directly above the brightest star in this three-color composite image, which covers 14.6´ × 13.4´ on the sky, is the high mass star formation complex known as K3-50. The cluster is located in the constellation Cygnus at a distance of about 8700 pc (28000 light years). The region is quite young. While the Sun is presently about 5 billion years old, this cluster is only around 10 to 100 thousand years old. Stars are generally considered massive if they are 10 times the mass of the Sun or larger. In the case of this complex good evidence exists that at least three of the stars are larger than 60 times the mass of the Sun (Howard et al. 1996, ApJ, 460, 744). In addition to these stars, at least four other massive stars are present in this region. High mass stars typically form in complex clusters, and this region is no exception. K3-50 is comprised of at least five different regions of high mass star formation. The southernmost region is visible at optical wavelengths and is one of the more evolved regions in the complex. Progressing northward, the regions of star formation are located deeper in the parent molecular cloud. Most of the nebular emission seen here is only detectable by observing in near-infrared, or even longer, wavelengths.
Image mosaic by S. Van Dyk (IPAC). Caption provided by E. Howard (UMass).


Is it the Black Hole of Calcutta? No, it's a dark, obscuring cloud of dust near the Galactic Plane (the cloud is at RA=17h35m46.84s Dec=-25d33m10.8s, J2000; in galactic coordinates, l=1.62, b=+3.77; this image covers 8.2´ × 12.5´ on the sky). The cloud is the entry ``1-457'' in the catalog by Feitzinger & Stuwe (1984, A&AS, 58, 365) of dark nebulae. Based on the (J-H, H-Ks) color-color diagram, we estimate that the extinction toward the center of the cloud is AV>20 mag.


This mosaic image of our dwarf irregular satellite neighbor, the Large Magellanic Cloud (LMC), covers 6.9° × 6.1° on the sky. (It has been binned from 1´´ pixels to 5´´ pixels.) The LMC is at a distance from us of 50 kpc (or 163,000 light years). The nebulosity and bright recent star formation seen so prominently in the optical are much diminished in the near-infrared. Only 30 Doradus (the Tarantula Nebula) is still relatively recognizable in this image. The galaxy's bar region, however, is quite prominent, as seen by 2MASS, as it is dominated by intermediate-age red giants. Also detected in the galaxy are bright red and blue supergiants, and a large number of asymptotic giant branch (AGB) stars. In particular, 2MASS is sensitive to the large quantity of dust-obscured red AGB stars and carbon stars, which are spatially distributed throughout the galaxy.
Image mosaic by E. Kopan (IPAC).


The molecular cloud and embedded star cluster Monoceros R2. The 2MASS image of a stellar cluster in the Mon R2 chain of reflection nebulae. At a distance of 830 pc (2700 light years), the Mon R2 cluster is one of the closest massive star-forming regions to the Sun that remains embedded in a molecular cloud. The cluster contains at least a few hundred pre-main sequence stars within a 0.4-pc diameter region, and likely has formed within the past few million years (Carpenter et al. 1997, AJ, 114, 198). The two blue patches of luminosity on either side of the Mon R2 cluster are illuminated by early B-type stars, and are part of a chain of about 30 such reflection nebulae that define the Mon R2 association (Herbst & Racine 1976, AJ, 81, 840). (The full field in the image covers 20.8' × 12.5'.)
Image mosaic by E. Kopan (IPAC).


The Galactic Center. This 2.2° × 3.9° image mosaic shows the Galactic Plane (the Plane of the Milky Way). The Galactic Center is the very luminous Ks-bright (reddish) source south of the image center. (The image is centered at RA=17h46m22.0s Dec=-27d58m20s [J2000].) This mosaic contains more than 1 million stars. Visible, even in the near-infrared, are the obscuring dust lanes that fill the Plane between us and the Galactic Center, located about 8.1 kpc (26400 light-years) away. However, with 2MASS, we are able to see farther through this dust than can be accomplished at visible wavelengths.
Image mosaic by E. Kopan (IPAC).
































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