哈勃望远镜发现发射星云双星团
Against a backdrop littered with tiny pinpricks of light glint a few, brighter stars. This whole collection is NGC 1858, an open star cluster in the northwest region of the Large Magellanic Cloud, a satellite galaxy of our Milky Way that boasts an abundance of star-forming regions. NGC 1858 is estimated to be around 10 million years old.
Open clusters are a type of star cluster with loose gravitational attraction between the stars, which causes the cluster to be irregularly shaped and its stars to be spread out. NGC 1858 is also an emission nebula, which is a cloud of interstellar gas that has been ionized by ultraviolet wavelengths radiating off of nearby stars. The gas of the nebula emits its own light at visible wavelengths, seen here as a faint cloud that populates the middle and bottom right of the image.
The stars within this young cluster are at different phases of their evolution, making it a complex collection. Within NGC 1858, researchers have detected a protostar, a very young, emerging star, indicating that star formation within the cluster may still be active or has stopped very recently. The presence of an emission nebula also suggests that star formation recently occurred here, since the radiation required to ionize the gas of the nebula comes from stars that only live a short time.
NGC 1858 is located about 160,000 light-years away in the constellation Dorado and contains multiple massive stars, which can be seen shining brightly throughout the center of the image. The cluster is located in a crowded area of the sky, and the large number of stars around the cluster makes it difficult to study alone. To survey these distant stars, scientists relied on the Hubble Space Telescope’s unique resolution and sensitivity at visible and infrared wavelengths.
Image Credit: NASA, ESA and G. Gilmore (University of Cambridge); Processing: Gladys Kober (NASA/Catholic University of America)
在点缀着点点微光的背景下，几颗更亮的恒星闪烁着光芒。这整个集合就是NGC 1858，一个位于大麦哲伦星云西北区域的疏散星团，大麦哲伦星云是我们银河系的一个卫星星系，拥有大量的恒星形成区。据估计，NGC 1858大约有1000万年的历史。
疏散星团是一种恒星之间具有松散引力的星团，这会导致星团形状不规则，其恒星分散开来。NGC 1858也是一个发射星云，这是一种星际气体云，被附近恒星的紫外线辐射电离。星云的气体在可见光波段发出自己的光，如图所示，在图像的中间和右下角有一片微弱的云团。
这个年轻星团中的恒星处于其演化的不同阶段，使其成为一个复杂的集合。在NGC1858中，研究人员发现了一颗原恒星，这是一颗非常年轻的新兴恒星，表明这个星团中的恒星形成可能仍然活跃，或者最近才停止。发射星云的存在也表明，恒星的形成是最近才发生，因为电离星云气体所需的辐射来自寿命很短的恒星。
NGC 1858位于剑鱼座，距离我们大约160,000光年，包含多颗大质量恒星，可以在整个图像中心看到它们的明亮光芒。该星团位于天空中拥挤的区域，星团周围的恒星数量众多，很难单独进行研究。为了观测这些遥远的恒星，科学家们依赖于哈勃太空望远镜在可见光和红外波长上独特的分辨率和灵敏度。
影像来源：NASA, ESA and G. Gilmore (University of Cambridge); 影像处理：Gladys Kober (NASA/Catholic University of America)