2MASS Picture of the Week Archive Captions

Atlas Image mosaic, covering 8´ × 8´ on the sky of the nearest star to our Sun, Proxima Centauri, which is the nearest member of the Centauri triple star system. It is about 1.295 parsecs (4.22 light years) from us (its parallax is less than the 1 arcsec which defines the parsec distance unit). It is quite red in the optical. This is because it is of very late spectral type, i.e., mid-M type, and therefore has a cool surface temperature. (In the 2MASS image, the star looks relatively "warm.") Proxima Cen is about 12000 astronomical units from Cen, which itself is at a somewhat larger distance from us of 1.347 pc. Proxima Cen is modestly "active," as a so-called "flare star," characterized by variable emission lines in its spectrum. The flares arise from a surprisingly active corona, similar to that of the Sun's (Wood et al. 2001, ApJ, 547, L49).


Atlas Image mosaic, covering 15.5´ × 15.5´ on the sky of the very famous Eagle Nebula, Messier 16 (M16, NGC 6611, IC 4703), also known as the Star Queen Nebula. A previous very nice near-infrared image of the Nebula appears here. Contrast these with the beautiful optical images by David Malin and the well-known HST image of the "Pillars", seen just northeast of the 2MASS image center. The nebular emission from excited gas seen in the optical images is no longer as prominent in the 2MASS image. Instead, we mostly see the blue light from the many young, massive stars in this open cluster reflecting (scattering) off dust in the region. The stellar density is also much larger in the 2MASS image, since we are peering through much of the dust which obscures starlight in the optical. New stars are still forming in the "Pillars" and in other dusty filaments seen in both the optical and near-infrared. The Eagle is a complex region of recent and ongoing star formation at the edge of molecular gas clouds. Image mosaic by S. Van Dyk (IPAC).


Atlas Image mosaic, covering 20.5´ × 20.5´ on the sky of the infrared source IRAS 20306+3841. Within this source (seen to the southeast in the 2MASS image), in the region Cygnus X and radio complex W69, Bica & Dutra (2001, A&A, 376, 434) recently catalogued the partly resolved young cluster embedded in the molecular gas, using the 2MASS Second Incremental Data Release. Another embedded cluster appears to the northwest. See the 2MASS color-color and color-magnitude diagrams. Image mosaic by S. Van Dyk (IPAC).


Atlas Image mosaic, covering 22´ × 16.5´ on the sky of NGC 6992, part of the Veil Nebula. NGC 6992 is a small part to the east of the much larger Veil, or Cygnus Loop, which is a middle-aged shell-type remnant of a supernova explosion which occurred in the Milky Way about 14,000 years ago (Levenson et al. 1998, ApJS, 118, 541). The ghostly, faint blue filaments seen in this 2MASS image may be due to shock-excited line emission from forbidden singly-ionized iron, which emits primarily in the J and H bands, as seen in the near-infrared for the remnant 3C391 (Reach et al. 2002, ApJ, 564, 302). The Veil measures about 3.8° × 2.7° across and is about 770 pc (2510 light years; Levenson et al.) from us. Uyaniker et al. (2002, A&A, 389, L61), from a recent multiwavelength study, suggest that the Cygnus Loop is not a single supernova remnant, but actually two interacting with each other. They also find evidence for a stellar remnant, possibly a neutron star, in the southern component of the remnant pair, implying that at least for the southern component, it was a star at least 10 times more massive than the Sun which exploded. Image mosaic by S. Van Dyk (IPAC).


Atlas Image mosaic, covering 6´ × 6´ on the sky of the globular cluster Messier 70 (M70). M70 is also known as NGC 6681. It is at a distance of about 9200 pc (30000 light years) from us, and it is about 2100 pc from the Galactic center. It is of intermediate metallicity, and Salaris & Weiss (2002, A&A, 388, 492) recently placed its age at about 11.7 Gyr. (The purple "haze" just south of the cluster's center is a known persistence artifact.)
































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