NGC 1232：一个大设计螺旋星系
(原标题: NGC 1232: A Grand Design Spiral Galaxy)
2024-01-01
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星系的迷人之处不仅在于它的可见性，还在于它的不可见性。超大望远镜捕捉到的大螺旋星系NGC 1232的细节就是一个很好的例子。可见的是由数百万颗明亮的恒星和黑暗的尘埃组成的，它们被围绕中心旋转的旋臂的引力漩涡所吸引。包含明亮蓝色恒星的疏散星团可以沿着这些旋臂散布，而密集星际尘埃的黑暗通道可以在它们之间散布。虽然看不见，但可以探测到的是数十亿颗暗淡的正常恒星和大片的星际气体，它们的质量如此之大，以至于主宰了内星系的动力学。主流理论指出，更多的物质是看不见的，其形式我们还不知道。这种无处不在的暗物质被认为部分是为了解释星系外围可见物质的运动。免费APOD讲座：2024年1月9日，纽约业余天文学家协会
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Galaxies are fascinating not only for what is visible, but for what is invisible. Grand spiral galaxy NGC 1232, captured in detail by one of the Very Large Telescopes, is a good example. The visible is dominated by millions of bright stars and dark dust, caught up in a gravitational swirl of spiral arms revolving about the center. Open clusters containing bright blue stars can be seen sprinkled along these spiral arms, while dark lanes of dense interstellar dust can be seen sprinkled between them. Less visible, but detectable, are billions of dim normal stars and vast tracts of interstellar gas, together wielding such high mass that they dominate the dynamics of the inner galaxy. Leading theories indicate that even greater amounts of matter are invisible, in a form we don't yet know. This pervasive dark matter is postulated, in part, to explain the motions of the visible matter in the outer regions of galaxies. Free APOD Lecture: January 9, 2024 to the Amateur Astronomers of Association of New York