2020 March 2

Sharpless-308: The Dolphin Nebula
Image Credit & Copyright:
Chilesope 2, Pleaides Astrophotography Team (Peking U.)

Explanation: Blown by fast winds from a hot, massive star, this cosmic bubble is much larger than the dolphin it appears to be. Cataloged as Sharpless 2-308 it lies some 5,200 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 in the featured expansive image is dominated by the glow of ionized oxygen atoms mapped to a blue hue.

Tomorrow’s picture: around the moon

Chilesope 2, Pleaides Astrophotography Team (Peking U.)

说明: 从一颗炙热的大质量恒星吹出的快速星风形成了图中这个巨大的比我们日常所见的海豚大得多的宇宙气泡。它在沙普利斯亮星表中的编号为2-308,位于大犬座,距离约5200光年,覆盖的天区范围略大于一个满月,对应的直径为60光年。产生气泡的大质量恒星是一颗沃尔夫-拉叶星(WR型星),是星云中心附近的一颗亮星。WR型星的质量是太阳质量的20倍以上,被认为处于大质量恒星演化的前超新星阶段。从这颗WR型星吹出的快速星风在扫掠早期演化阶段移动较慢的物质时,形成了气泡状星云。这个被风吹动的星云的年龄约为7万年。图像中捕捉到的相对微弱的辐射主要是电离氧原子的辉光被映射成了蓝色。

明日的图片: around the moon

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