2019 November 12

NGC 3717: A Nearly Sideways Spiral Galaxy
Image Credit:
ESA/Hubble & NASA, Processing: D. Rosario

Explanation: Some spiral galaxies are seen nearly sideways. Most bright stars in spiral galaxies swirl around the center in a disk, and seen from the side, this disk can be appear quite thin. Some spiral galaxies appear even thinner than NGC 3717, which is actually seen tilted just a bit. Spiral galaxies form disks because the original gas collided with itself and cooled as it fell inward. Planets may orbit in disks for similar reasons. The featured image by the Hubble Space Telescope shows a light-colored central bulge composed of older stars beyond filaments of orbiting dark brown dust. NGC 3717 spans about 100,000 light years and lies about 60 million light years away toward the constellation of the Water Snake (Hydra).

NGC 3717:几乎侧向的旋涡星系
ESA/Hubble & NASA, Processing: D. Rosario

说明:一些旋涡星系几乎只能看到其侧面。旋涡星系中的多数亮星都围绕着星系盘中心旋转,从侧面看,这个盘面看起来非常纤薄。一些旋涡星系看起来甚至比NGC 3717还要纤薄,而NGC 3717实际上只是倾斜了一点。旋涡星系之所以会形成盘面是因为原始气体与其自身发生相撞,并在向内落下时冷却下来。行星也可能出于类似的原因绕着盘面运行。这幅由哈勃太空望远镜拍摄的特征影像呈现了一个浅色的中央凸起,它是由暗棕色丝状尘埃之外的古老恒星组成。NGC 3717的跨度约10万光年,位于长蛇座方向距离我们约6千万光年远。

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