Cygnus: Bubble and Crescent
Credit & Copyright: Abdullah Al-Harbi
Explanation: As stars die, they create clouds. Two stellar death clouds of gas and dust can be found toward the high-flying constellation of the Swan (Cygnus) as they drift through rich star fields in the plane of our Milky Way Galaxy. Caught here within the telescopic field of view are the Soap Bubble (lower left) and the Crescent Nebula (upper right). Both were formed at the final phase in the life of a star. Also known as NGC 6888, the Crescent Nebula was shaped as its bright, central massive Wolf-Rayet star, WR 136, shed its outer envelope in a strong stellar wind. Burning through fuel at a prodigious rate, WR 136 is near the end of a short life that should finish in a spectacular supernova explosion. Discovered in 2013, the Soap Bubble Nebula is likely a planetary nebula, the final shroud of a lower mass, long-lived, Sun-like star destined to become a slowly cooling white dwarf. Both stellar nebulas are about 5,000 light-years distant, with the larger Crescent Nebula spanning about 25 light-years across. Within a few million years, both will likely have dispersed.
Your Sky Surprise: What picture did APOD feature on your birthday? (post 1995)
Tomorrow’s picture: blue supermoon
影像提供与版权: Abdullah Al-Harbi
说明: 恒星濒死时会创造星云。这二团恒星死亡时所产生的气体与尘埃云，漂流在银河系盘面天鹅座方向的富星场里。位在这幅望远镜视野里的皂泡星云（左下）及眉月星云（右上），都是由处在最终演化阶段的恒星所产生的。其中，亦名为NGC 6888的眉月星云，是由位在其中心的明亮大质量沃尔夫-拉叶星（WR 136），以强烈的恒星风抛出它的外层气壳所形成的。而以惊人速率消耗核燃料的WR 136，处在它短暂生命的终点附近，最后会以壮观的超新星爆炸谢幕。2013年才发现的皂泡星云，很可能是个行星状星云；它是一颗注定将成为缓缓冷却白矮星的长寿、小质量类太阳恒星所抛出之气体寿衣。这二团星云的距离都在5,000光年上下，较庞大的眉月星云跨幅约为25光年。在数百万年之内，这二团星云可能都会消散匿踪。
明日的图片: blue supermoon