Wind Blown Bubbles
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Most stars expel material into their surroundings during their lives, and/or at their deaths. This material enriches the galaxy with "heavy" elements, affects the evolution of supernova remnants which sweep over it, and ultimately may end up back inside a later generation of stars (remember that we are all made of star dust!). The top left image is of the Bubble Nebula, a rare main-sequence wind-blown-bubble (WBB). The top right image is of the Crescent Nebula, surrounding the Wolf-Rayet star WR136. Material from the WR star is sweeping up ejecta from an earlier stage in the evolution of this star. Massive stars are born in clusters, and larger "superbubbles" form from the combined influence of the individual winds and explosions of the stars that make up the cluster. This process is seen at a relatively early stage in the Spitzer image of RCW 79 to the right. On even larger scales, bubbles and voids are seen throughout the galaxy, as shown in the image below. |
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