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| | The Orion Cloud and Association |
 | | In the direction of the constellation Orion, approximately centered on the Great Orion Nebula M42 and M43, there drifts a giant cloud of interstellar gas and dust within the Milky Way galaxy. |
 | | These young stars make up the so-called Orion OB1 Association; OB because the most massive, most luminous, and simultaneously hottest of these stars belong to spectral types O and B. Because they are so luminous, they use up their nuclear fuel quickly and have only a short time to live. |
 | | The stars of the Orion Nebula, M42 and M43, form a subset of this group, and are sometimes separately counted as subgroup 1d, the very youngest stars of the Orion OB1 association. |
| www.seds.org /messier/more/oricloud.html (693 words) |
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