2MASS Picture of the Week Archive Captions

Atlas Image mosaic, covering 15.0´ × 15.0´ on the sky, showing the infrared sources RAFGL 5180 and 5182 (IRAS 06058+2138 and 06061+2151, respectively). These are both embedded dense clusters of massive young stars in the Gemini OB1 molecular cloud complex (Carpenter, Snell, & Schloerb 1995, ApJ, 450, 201), near the HII region Sharpless 247. These data are part of the Spring 1999 data release. Image mosaic by S. Van Dyk (IPAC).


Atlas Image, covering 5.4´ × 5.4´ on the sky, showing the Eskimo Nebula (NGC 2392). This is a planetary nebula, showing a double ring structure. Planetary nebulae are formed as low-mass stars, like the Sun, reach the end of their lives and lose their outer envelopes to the interstellar medium. From an analysis of the nebula's kinematics, O'Dell, Weiner, & Chu (1990, ApJ, 362, 226) proposed a model where the observer is looking into a bipolar stellar wind flow from the hot central star (seen in the image brightly at the nebula's center). The star first lost mass during the extended red giant envelope stage from the equator of the precursor star, forming the outer disk, or ring, ~5300 yr ago; the inner disk, or ring, with an age of ~1000 yr, represents a more recent, strong, ongoing wind. The central star will eventually evolve to a white dwarf, as the nebular gas dissipates. Latter et al. (1995, ApJS, 100, 159) previously imaged the Eskimo in the near-infrared; in the case of this nebula, the near-IR emission is dominated by reradiated light from the central star by nebular dust likely formed during the precursor star's asymptotic giant branch phase. These data are part of the Spring 1999 data release.


Atlas Image, covering 4.4´ × 6.2´ on the sky, showing the Solar System asteroid 2 Pallas, one of the most studied and the second brightest of these minor planets. These data are part of the Spring 1999 data release, which will contain a number of other detections of known asteroids. Identification of the objects takes place as part of the 2MASS pipeline processing. This image appears in the 2MASS Image Gallery of Solar System objects. Near-infrared photometry of asteroids can tell much about the Sun-reflecting surface composition, for example, the amount and nature of any organic solids or ices coating the asteroid's rocky interior. The properties of this regolith affect the albedo, or reflectivity, of the asteroid. Using thermal emission models for asteroids, for instance, a number of parameters, including diameter and thermal history, can be derived. The observed colors and inferred compositions of asteroids can place constraints on the thermal environment in the early Solar System, providing clues to the formation of the major planets, including the Earth.


An image mosaic, covering 14.2´ × 14.2´ on the sky, of the star formation complex and young stellar outflow Cepheus A, at 725 pc (2400 light years) distant. The infrared bright core of the radio source Cepheus A, to the northwest in the mosaic, contains a number of highly obscured young, massive stars and molecular gas. A complex molecular outflow extends from the core. The core itself is obscured by more than 100 magnitudes of optical extinction! Reflection nebulae, bright Herbig-Haro objects, bow shocks, and jets are also seen in the complex (Hartigan et al. 1996, AJ, 111, 1278). The bright nebula to the southeast in the mosaic is IRAS 22551+6139, also a probable young stellar object. These data are part of the Spring 1999 data release. Image mosaic by R. Cutri (IPAC).


This image of the nearby barred spiral galaxy Maffei 2, covering 12.0´ × 14.4´ on the sky, appears in the 2MASS Image Gallery of extragalactic objects. Maffei 2 is located near the Galactic Plane, at galactic longitude l=136.50 and latitude b=-0.33, and suffers from ~5 magnitudes of visual extinction. As such, it wasn't recognized as a galaxy until it was initially detected in the near-infrared as an anomalous source by Maffei (1968. PASP, 80, 618) and its morphological type was identified by Spinrad et al. (1971, ApJ, 163, L25). Maffei 2, at a distance of about 5 Mpc (16.3 million light years), and its nearby elliptical companion, Maffei 1 (see the Image Gallery), highlight the importance of the near infrared, and, specifically, 2MASS, as a window on galaxies behind the Milky Way disk in the so-called "Zone of Avoidance", where they are hidden due to Galactic dust. Although its gas kinematics are consistent with those of other barred galaxies, Maffei 2 in the infrared, radio continuum and H I emission appears markedly disturbed. The structural asymmetries, as well as the nuclear starburst, are possibly driven by an ongoing merger with a small satellite companion galaxy (Hurt, Turner, & Ho 1996, ApJ, 466, 135). These data are part of the Spring 1999 data release. Image mosaic by R. Cutri (IPAC).
































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