Dark nebulae, consisting mostly of cold molecular hydrogen, are revealed only by the presence of luminous material nearby or along the line of sight. Photographs of the Milky Way star clouds show numerous ghostly silhouettes, many adjacent to bright emission nebulae. Michael Stecker’s wide-angle photograph of the Milky Way, viewed from our “insider” vantage point, should be compared with the image of external galaxy NGC 891 discussed in Chapter 5, where similar dark nebulae and adjacent star fields plus bright nebulae along the galactic equator are seen edge-on from an “outsider” viewpoint. Pine trees on Mt Pinos are silhouetted against the Sagittarius Milky Way in this wide-field view obtained with a 3-minute exposure through a Pentax 165 mm f/2.8 lens and Pentax 6 × 7 format camera, using Kodak Pro 1000 PMZ-120 film.
KeywordsMolecular Cloud Star Cluster Supernova Explosion Bright Star Open Star Cluster
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