The investigation of dark nebulas has been facilitated by a new discovery . 对暗星云的研究被一种新发现所推进。
2.
This can be a useful technique for seeing faint " nebulosity " - it ' s often a lot easier to see such nebulosity as faint shading against a white background rather than as " not quite black " against a black background 这个选项对于看暗星云是十分有用的-暗星体显示在亮背景上比“不是非常黑”的暗星体显示在黑背景上要容易观察的多。
