2025年4月10日
38 Hours with the M81 Group
Image Credit & Copyright: Daniel Yang K.
Explanation: From a garden on planet Earth, 38 hours of exposure with a camera and small telescope produced this cosmic photo of the M81 galaxy group. In fact, the group’s dominant galaxy M81 is near the center of the frame sporting grand spiral arms and a bright yellow core. Also known as Bode’s galaxy, M81 itself spans some 100,000 light-years. Near the top is cigar-shaped irregular galaxy M82. The pair have been locked in gravitational combat for a billion years. Gravity from each galaxy has profoundly affected the other during a series of cosmic close encounters. Their last go-round lasted about 100 million years and likely raised density waves rippling around M81, resulting in massive star forming regions arrayed along M81‘s spiral arms. M82 was left with violent star forming regions too, and colliding gas clouds so energetic that the galaxy glows in X-rays. In the next few billion years, their continuing gravitational encounters will result in a merger, and a single galaxy will remain. Another group member, NGC 3077 is below and left of the large spiral M81. Far far away, about 12 million light-years distant the M81 group galaxies are seen toward the northern constellation Ursa Major (the Great Bear). But in the closer foreground the wide-field image is filled with integrated flux nebulae whose faint, dusty interstellar clouds reflect starlight above the plane of our own Milky Way galaxy.
Tomorrow’s picture: a matinee
38小时长曝光的星系群M81
影像提供与版权: Daniel Yang K.
说明: 在地球上的一座花园里，透过小望远镜与相机进行38小时的长曝光，拍下了这幅令人赞叹的M81星系群影像。于视野中心，最醒目的是拥有壮丽螺旋臂与明亮黄色核心、直径约10万光年、亦名为波德星系的M81星系。视野顶缘的雪茄状星系，则是分类为不规则星系的M82。这对星系在过去的10亿年之中，一直透过重力进行互扰，在一次次的近距离遭遇中，对彼此施加重大的影响。约于1亿年前的最新一次接近中，所激发的密度波在M81的螺旋臂上，造就了大量的恒星诞生区。而M82也因此次的剧烈互扰，发生爆发性的恒星诞生与气体云碰撞，并发出强烈的X射线辉光。在未来的数十亿年里，这两个星系还会继续缠斗，最终让它们合并成单个大星系。而在大螺旋星系M81的左下方，还可看到M81星系群的另一个成员星系NGC 3077。M81星系群位于北天的大熊座方向，离我们约1,200万光年远。在这幅广角影像的前景里，还可见到许多位于银河系盘面上方，微微反射星光、名为共照耀星云（IFN）的昏暗星际尘埃云。
明日的图片: a matinee
