2MASS Picture of the Week Archive Captions

Atlas Image mosaic, covering 40´ × 40´ on the sky, of the War and Peace Nebula, aka NGC 6357. The nebula attained this colloquial name, due to its appearance in the mid-infrared, as seen by the Midcourse Space Experiment (MSX) scientists. They see the bright portion of the nebula, to the northwest, as looking like a dove, while the mid-IR filaments to the east seem to trace out a human skull. The "dove" is still seen in the 2MASS near-infrared image, but the "skull" is not nearly as apparent as in the MSX image. As can be seen in a much larger mosaic, NGC 6357 (to the north) and NGC 6334 (to the south) are located not far from each other, along the Galactic plane, just south and west of the Galactic center. (N.B.: The full NGC 6357 mosaic is 4.9 Mb in size.) Image mosaic by S. Van Dyk (IPAC). (Larger NGC 6334/6357 mosaic by E. Kopan & R. Hurt, IPAC.)


Atlas Image mosaic, covering 42´ × 42´ on the sky, of the Cat's Paw, or Bear Claw, Nebula, aka NGC 6334. Image mosaic by S. Van Dyk (IPAC).


Atlas Image, covering 4.5´ × 4.5´ on the sky, of the comet C/1997 J2 (Meunier-Dupouy). A large number of comets have been serendipitously imaged during the routine course of 2MASS. A list of comets in the Second Incremental Data Release can be found here. This comet, "une comète Française," discovered in 1997 May independently by Meunier and Dupouy (also by Jean Mueller, Palomar Observatory), has a relatively large perihelion distance (3.76 AU), and visually reached two maxima, both at about 10.5 visual magnitudes, in 1997 November and, again, in 1998 August, the second when it was at its smallest distance from Earth (2.49 AU). The 2MASS images were made on 1998 October 22, as the comet became more distant and fainter (about 12 visual magnitudes). The apparent coma diameter at that time was about one arcminute. Its spectrum, or component colors, most closely resembles the light it is reflecting, that is, the light of our Sun.


Atlas Image mosaic, covering 8.0´ × 8.0´ on the sky, of the globular cluster UKS 1 (aka UKS 1751-24.1). This cluster, in the Galactic bulge and near the Galactic center (l=5.1°, b=0.8°), is quite reddened and in a very crowded stellar field. Ortolani, Bica, & Barbuy (1997, A&AS, 126, 319) present optical photometry of the cluster and find that the extinction is nearly 11 visual magnitudes, that the distance to the cluster is 7.4 kpc (24,124 light years), and that the cluster may be metal-rich. Near-infrared photometry was previously obtained for the stars in the cluster, along with those for 19 other bulge clusters, by Minniti, Olszewski, & Rieke (1995, AJ, 110, 1686). Their main conclusion is that there is no apparent difference between the majority of the bulge stellar population and that of the most metal-rich bulge globular clusters. Click here for a 2MASS color-color diagram for UKS 1, and here for a color-magnitude diagram. With the caveat that the 2MASS pipeline photometry is not accurate in crowded regions, such as globular clusters, the photometry tends to suggest that, given the Ortolani et al. distance, for a 14 Gyr isochrone with solar metallicity, the extinction to the cluster is more at about 8.5 visual magnitudes. Image mosaic by S. Van Dyk (IPAC).


Atlas Image mosaic, covering 12.0´ × 12.0´ on the sky, of NGC 2626. The nebula, at a distance of about 1 kpc (3300 light years), is primarily reflecting the light from the bright blue (B1-type) 10th-magnitude star, CD -40°4432, which is embedded in it. (The star is seen toward the center of, and appears to be blended with another star in, the 2MASS image.) The infrared-bright jet-like nebula seen north of the blue star is the Herbig-Haro object HH 132, emanating from the bright infrared source IRAS 08337-4028. The bright star east and a bit north of CD -40°4432 is the pulsating variable star EM Velorum, a possible intermediate-mass Herbig Ae star. (The bright star at the top of the 2MASS image is IRAS 08338-4022.) Mueller & Graham (2000, PASP, 112, 1426), based on optical narrow-line imaging, have identified a number of H-bright sources in the field, which they associate with lower-mass, young K-type dwarfs, some of which may be T Tauri stars. IRAS 08337-4028 is most likely an embedded forming star, but the 2MASS image reveals a number of other young stellar objects as well, embedded in the dark cloud immediately north of NGC 2626 and elsewhere in the reflection nebula. Image mosaic by S. Van Dyk (IPAC).
































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