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Westerhout 5 (Sharpless 2-199, LBN 667, Soul Nebula) is emission nebulae in Cassiopeia. Several small open clusters are embedded in the nebula: CR 34, 632, and 634 (in the head) and IC1848 (in the body). The object is more commonly called by the cluster designation IC1848. Small emission nebula IC 1871 is present just left of the top of the head, and small emission nebulae 670 and 669 are just below the lower back area. This complex is the eastern neighbor of IC1805 (Heart Nebula) and the two are often mentioned together as the "Heart and Soul". Image: W5 cropped.jpg|Generations of stars can be seen in this infrared portrait from NASA's Spitzer Space Telescope. Image:Heart and Soul nebulae.jpg|The Heart Nebula and Westerhout 5 are seen in this infrared mosaic from NASA's WISE telescope. ==Star formation== W5, a radio source within the nebula, spans an area of sky equivalent to four full moons and is about 6,500 light-years away in the constellation Cassiopeia. Like other massive star-forming regions, such as Orion and Carina, W5 contains large cavities that were carved out by radiation and winds from the region's most massive stars. According to the theory of triggered star formation, the carving out of these cavities pushes gas together, causing it to ignite into successive generations of new stars. The image in the gallery above contains some of the best evidence yet for the triggered star formation theory. Scientists analyzing the photo have been able to show that the ages of the stars become progressively and systematically younger with distance from the center of the cavities. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Westerhout 5」の詳細全文を読む スポンサード リンク
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