Title:[0276] Faint Nebulosity near Orion and Horsehead Nebula Caption:This wide-angle picture of the Orion region has been made to reveal the extensive network of very faint filaments that are traceable over most of the constellation. These faint features are optical evidence of a substantial dark cloud of molecular gas and dust, which dominate at radio wavelengths. Where hot stars are closely associated with the molecular cloud, a nebula appears. By far the brightest of these is the Orion Nebula, M42. This spectacular object is so bright that its light is reflected from filaments of the dark cloud some distance away. In contrast, the wisps of the Horsehead Nebula are much fainter but even here faint tendrils of nebulosity show that the nebula is much more extensive than is generally realized. Copyright:(c) 1987 Royal Observatory Edinburgh Credit:D. F. Malin

Title:[1071] Infrared image of NGC 7538 Caption:An infrared image of NGC 7538, a region of massive star formation within our Galaxy. The colors in the infrared image were produced by taking three images through filters at three different wavelengths (1.2, 1.65 and 2.2 microns) and combining them, similar to the method used by color television. NGC 7538 is located about 7,000 light years from Earth. The red object in the lower left is a very young star heavily embedded in the molecular cloud from which it formed; the blue extension to the lower right from this young star is caused by radiation scattered from dust grains within the cloud. The patch of interstellar hydrogen is ionized by ultraviolet radiation from massive young stars. Kitt Peak National Observatory 1.3-meter telescope photo taken by Ian Gatley, 1989. Copyright: Credit:National Optical Astronomy Observatories/Dr. Ian Gatley

Title:[0579] Orion Nebula: optical image Caption:This optical photograph of the Orion Nebula, taken with the Kitt Peak 4-meter telescope, covers ~1.5 x 1 degrees. At a distance of 1,600 light years and extending 15 light years across, the Orion nebula consists of turbulent ionized gas (60% hydrogen and 38% helium) and dust (2%) heated by the ultraviolet light of hot young stars. The radiation source for the large nebula is the Trapezium, a cluster of four bright stars (with apparent magnitudes from 5.4 to 8.0). The smaller round nebula (M43) to the north of Orion is heated by a single star that shines as brightly as several thousand Suns. The Orion nebula lies at the edge of a large cloud of cold gas and dust, thus small patches of dust obscure part of the radiation from the Orion nebula and appear as dark patches in the optical photograph. A giant molecular cloud of cold material, which lies slightly behind the Orion nebula, is believed to contain newly forming stars. Copyright:(c) Smithsonian Astrophysical Observatory Credit:Courtesy of National Optical Astronomy Observatories