2MASS Picture of the Week Archive Captions

Atlas Image mosaic, covering 5.0´ × 5.0´ on the sky, of the planetary nebula NGC 3132, known to amateur astronomers as the "Eight-Burst" or "Southern Ring" Nebula. The nebula was spectacularly imaged in the optical in a number of bands by the Hubble Space Telescope. The large wind-blown cavity in the nebula is also obvious in the near-infrared 2MASS image, as is much of the filamentary structure and extended emission. In the near-infrared most of the emission from NGC 3132 appears in the Ks (2.17 µm) band, giving the planetary nebula the reddish color in the image. Planetary nebulae are formed as low-mass stars, like our Sun, reach the end of their lives and lose their outer envelopes to the interstellar medium. The bright source within the nebula is the hot central star, originally the core of the dying star, which will eventually become a white dwarf and cool off over billions of years. Image mosaic by S. Van Dyk (IPAC).


Atlas Image, covering 7.0´ × 7.0´ on the sky, of the giant elliptical galaxy Messier 60 (M60), aka NGC 4649, Arp 116, VV 206. This galaxy is a member of the Virgo Cluster of galaxies. Like its fellow Virgo member, the giant elliptical M87, M60 shows (very weak) jets and radio lobes, indicative of an active nucleus and the possible presence of a central supermassive black hole of about 1 billion solar masses (di Matteo & Fabian 1997, MNRAS, 286, L50). The smaller galaxy to the northeast of NGC 4649 in the 2MASS image is the spiral galaxy NGC 4647. The small purplish spot just to the north of NGC 4649 is a known persistence artifact, left temporarily on the 2MASS detectors by the bright nuclear region of the elliptical galaxy.


Atlas Image Mosaic, covering 8.0´ × 12.0´ on the sky, of the open star cluster Messier 103 (NGC 581). Sanner et al. (1999, A&A, 349, 448) find, from optical photometry of stars in M103, that the cluster is at a distance of about 2900 pc (9450 light years), behind a bit more than a magnitude of visual extinction, and formed about 16 million years ago. Their analysis indicates that the so-called initial mass function for the cluster may be somewhat steeper generally than other open star clusters. The purplish "stars" trailing northward from the brightest stars in the 2MASS image are known persistence artifacts; diffraction spike artifacts are also seen around these bright stars. Click here to obtain a 2MASS color-color diagram for M103; the cyan line is the dwarf stellar track, the red line is the giant track (Bessell & Brett 1988, PASP, 100, 1134). Click here to obtain the color-magnitude diagram; the theoretical isochrone (in green) agrees with the optically-derived distance, extinction, and age for the cluster. Image mosaic by S. Van Dyk (IPAC).


Atlas Image Mosaic, covering 50.0´ × 50.0´ on the sky, of the heart of the Virgo Cluster of galaxies. This famous galaxy cluster, seen toward the constellation Virgo and covering in total more than 7° on the sky, is the closest large cluster to us, at a distance of about 17 Mpc (55 million light years). Together with other nearby groups and clusters, the Local Group of galaxies, of which the Milky Way is a member, form a much larger organizational unit, the Local Supercluster of galaxies. The cluster was first discovered by Charles Messier in the late 18th century; hence, many of its component galaxies are Messier objects. To the center right of this near-infrared mosaic are the two giant elliptical galaxies, Messier 86, or M86, and M84. Other smaller spiral galaxies are also seen in this image. Not included in this image of the cluster heart is the giant elliptical, M87, to the southeast, with its famous gaseous jet, emanating from a central supermassive black hole in the galaxy. Image mosaic by T. Jarrett (IPAC). (N.B.: The full mosaic is 6.0 Mb in size!)


Atlas Image Mosaic, covering 7.0´ × 7.0´ on the sky, of the star cluster NGC 7129. Star formation is still occurring in this young cluster. The bright reddish embedded star northeast of the image center is the Herbig Ae/Be star LkH 234, which is a source of molecular outflows. Farther to the northeast is the Herbig-Haro object HH 105. The various other knots and filaments are also indicative of outflow from the cluster stars (Eisloffel 2000, A&A, 354, 236). A long snake-like bright filament can be seen running along the southeast of the cluster. Emission from this filament, seen particularly at 2.12 µm (in the Ks band), appears to be due to flourescence, excited by LkH 234 (Noriega-Crespo et al. 2001, in preparation). A curious-looking possible outflow object can also be seen to the south of the star cluster. Image mosaic by S. Van Dyk (IPAC).































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