Dark shapes with bright edges winging their way through dusty NGC 6188 are tens of light-years long. The emission nebula is found near the edge of an otherwise dark large molecular cloud in the southern constellation Ara, about 4,000 light-years away. Formed in that region only a few million years ago, the massive young stars of the embedded Ara OB1 association sculpt the fantastic shapes and power the nebular glow with stellar winds and intense ultraviolet radiation. The recent star formation itself was likely triggered by winds and supernova explosions, from previous generations of massive stars, that swept up and compressed the molecular gas. At the estimated distance of NGC 6188, the picture spans about 200 light-years. At the right of the image, beautiful emission nebula NGC 6164 was created by a rare, hot, luminous O-type star, some 40 times as massive as the Sun. Seen at the center of the cosmic cloud, the star is a mere 3 to 4 million years old. In another three to four million years the massive star will end its life in a supernova explosion. Spanning around 4 light-years, the nebula itself has a bipolar symmetry. That makes it similar in appearance to more familiar planetary nebulae - the gaseous shrouds surrounding dying sun-like stars. Also like many planetary nebulae, NGC 6164 has been found to have an extensive, faint halo, revealed in this deep telescopic image of the region. Expanding into the surrounding interstellar medium, the material in the halo is likely from an earlier active phase of the O star. NGC 6164 is 4,200 light-years away in the southern constellation of Norma. (text adapted from APOD). Apo TEC140 (140/f7.2) - FLI Proline 16803 - Ha (200m) OIII (480m) R (90m) G (120m) B (150m) - Warrumbungle Observatory, Coonabarabran, NSW, Australia
Why is the Horsehead Nebula surrounded by a bubble? Although hard to make out, the famous Horsehead Nebula is the slight dark indentation in the bright streak just to the right of the image center. Glowing like an emission nebula, the origin of the bubble, known as Barnard's Loop, is currently unknown. Progenitor hypotheses include the winds from bright Orion stars and the supernovas of stars long gone. Barnard's Loop is too faint to be identified with the unaided eye. The nebula was discovered only in 1895 by E. E. Barnard on long duration film exposures. The above image was taken through RGB filters and improved by data coming from hydrogen filtered light to bring out detail. To the left of the Horsehead Nebula, visible as a small dark indentation, is the photogenic Flame Nebula while close to the right upper corner is shining the famous M42 nebula (text adapted from APOD). Mosaic of two frames collecting a total of 16 hours of light Pentax 67 EDIF 300mm f/4 - FLI Proline 16803 - Ha (240m) R (180m) G (320m) B (240m) - Warrumbungle Observatory, Coonabarabran, NSW, Australia
A variety of stars and nebulae can be found towards the constellation of Sagittarius. Dense fields of stars laced with dark lanes of dust crowd this region only a few degrees from the center of our Galaxy. Prominent nebulae include the red Lagoon Nebula (M8) in the center and the multicolored Trifid Nebula (M20) in the upper right. Another one, NGC 6559, is at the left of M8, separated from the larger nebula by a dark dust lane. All three are stellar nurseries about five thousand light-years or so distant. In this digital composition, the dominant red color of the emission nebulae is due to glowing hydrogen gas energized by the radiation of hot, young stars. The contrasting blue hues, most striking in the Trifid as well as NGC 6559, are due to dust reflected starlight. The bright HII region left of the Trifid is Sh-34 while the one closest to the bottom right corner is Sh-22. Also visible over Sh-34 the rainbow trace left by an asteroid. Almost at the center of this image is the open cluster M21 (text adapted from APOD). Pentax 67 EDIF 300mm f/4 - FLI Proline 16803 - Ha (120m) R (40m) G (40m) B (40m) - Warrumbungle Observatory, Coonabarabran, NSW, Australia
