SH2-308：海豚头星云

2021年10月21日

SH2-308: The Dolphin-Head Nebula
Image Credit & Copyright: Nik Szymanek

Explanation: Blown by fast winds from a hot, massive star, this cosmic bubble is huge. Cataloged as Sharpless 2-308 it lies some 5,000 light-years away toward the constellation of the Big Dog (Canis Major) and covers slightly more of the sky than a Full Moon. That corresponds to a diameter of 60 light-years at its estimated distance. The massive star that created the bubble, a Wolf-Rayet star, is the bright one near the center of the nebula. Wolf-Rayet stars have over 20 times the mass of the Sun and are thought to be in a brief, pre-supernova phase of massive star evolution. Fast winds from this Wolf-Rayet star create the bubble-shaped nebula as they sweep up slower moving material from an earlier phase of evolution. The windblown nebula has an age of about 70,000 years. Relatively faint emission captured by narrowband filters in the deep image is dominated by the glow of ionized oxygen atoms mapped to a blue hue. Presenting a mostly harmless outline, SH2-308 is also known as The Dolphin-head Nebula.

Tomorrow’s picture: it’s a comet

SH2-308：海豚头星云
影像提供与版权: Nik Szymanek

说明: 这团由炽热大质量恒星的高速恒星风所吹出的宇宙气泡，极为庞大。编录号为夏普利斯2-308 (Sharpless 2-308)的这团星云，位在大犬座方向，离我们约有5,000光年远，遮盖的天区稍大于满月。依它所在的距离来换算，这团星云的直径大约为60光年。造就这个泡泡的大质量恒星，则是位在星云中心附近的明亮沃夫-瑞叶型恒星。由于沃夫-瑞叶型恒星的质量是太阳的20倍以上，演化非常快速，它目前可能处在短暂的前超新星阶段。来自这颗沃尔夫·拉叶星的高速恒星风，推扫在先前演化阶段抛出的较慢速移动物质，形成了这团形如气泡的星云。这团由风吹成的星云，年龄在70,000年左右。在这幅深空影像里，较暗淡的辐射是透过窄波段滤镜所拍摄，其中最主要的是以蓝色渐层呈现的电离氧原子辉光。因它与人无害的外观，SH2-308另有海豚头星云的称号。

明日的图片: it’s a comet