Astronomy Picture of the Day——狮子座三重星系
The Leo Trio
Image Credit & Copyright: Markus Bauer
Explanation: This group is popular in thenorthern spring. Famous as the Leo Triplet, the three magnificent galaxiesgather in one field of view. Crowd pleasers when imaged with even modesttelescopes, they can be introduced individually as NGC 3628 (left), M66 (bottomright), and M65 (top). All three are large spiral galaxies but they tend tolook dissimilar because their galactic disks are tilted at different angles toour line of sight. NGC 3628, also known as the Hamburger Galaxy, is temptinglyseen edge-on, with obscuring dust lanes cutting across its puffy galacticplane. The disks of M66 and M65 are both inclined enough to show off theirspiral structure. Gravitational interactions between galaxies in the group have left telltale signs, including the tidal tails and warped, inflated disk of NGC3628 and the drawn out spiral arms of M66. This gorgeous view of the regionspans almost two degrees (four full moons) on the sky. The field covers about amillion light-years at the trio's estimated distance of 30 million light-years.Of course the spiky foreground stars lie within our own Milky Way.
狮子座三重星系
这个星系群在春季北方的天空很容易见到。闻名遐迩的狮子座三重星系是由聚集在同一片视野中的三个美丽星系构成的。这些星系分别是NGC3628（图像左侧）、M66（图像右下方）和M65（图像顶部），这三个星系都是较大的螺旋星系，因此在普通望远镜下也能被拍摄到。虽然都是旋涡星系，但它们看起来却有所不同，因为它们的星系盘与我们的视线夹角不同。在这幅图像中，亦称为汉堡星系的NGC 3628是侧对我们的，模糊的尘埃带切过其膨胀的星系盘。而M65和M66的星系盘足够倾斜，对我们呈现出它们完整的旋涡结构。星系间的引力相互作用产生了一些显著的效应，包括NGC 3628的潮汐尾和扭曲且膨胀的星系盘，M66的冗长旋臂等等。这幅壮丽的影像跨越了约两度（四个满月）的天区。以狮子座三重星系估计三千万光年的距离来计算，该区域跨度约为一百万光年。当然，这些带有星芒的前景恒星位于我们的银河系内。
参考文献：
https://apod.nasa.gov/apod/image/1904/LeoTrioBauer.jpg
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Astronomy Picture of the Day——螺旋星系M81