北极星：北极星和周围的尘埃
(原标题: North Star: Polaris and Surrounding Dust)
2023-04-11
浏览次数: 21
为什么北极星被称为北极星？首先，北极星是离地球北自转轴最近的明亮恒星。因此，当地球转动时，恒星似乎围绕北极星旋转，但北极星本身总是保持在同一个向北的方向——使它成为北极星。由于没有明亮的恒星靠近地球的南自转轴，所以目前没有明亮的南星。几千年前，地球的自转轴指向一个稍微不同的方向，因此织女星就是北极星。虽然北极星不是天空中最亮的星，但它很容易定位，因为它几乎与北斗七星杯中的两颗星对齐。北极星位于这张8度宽的特色图像的中心附近，这是一张由数百张曝光照片组成的数字合成照片，在整个画面中都显示出综合通量星云（IFN）的微弱气体和尘埃，最左边是球状星团NGC 188。造父变星北极星的表面缓慢地脉动，导致这颗著名的恒星在几天的时间里亮度变化了几个百分点。探索你的宇宙：随机APOD生成器
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Why is Polaris called the North Star? First, Polaris is the nearest bright star toward the north spin axis of the Earth. Therefore, as the Earth turns, stars appear to revolve around Polaris, but Polaris itself always stays in the same northerly direction -- making it the North Star. Since no bright star is near the south spin axis of the Earth, there is currently no bright South Star. Thousands of years ago, Earth's spin axis pointed in a slightly different direction so that Vega was the North Star. Although Polaris is not the brightest star on the sky, it is easily located because it is nearly aligned with two stars in the cup of the Big Dipper. Polaris is near the center of the eight-degree wide featured image, a digital composite of hundreds of exposures that brings out faint gas and dust of the Integrated Flux Nebula (IFN) all over the frame as well as the globular star cluster NGC 188 on the far left. The surface of Cepheid Polaris slowly pulsates, causing the famous star to change its brightness by a few percent over the course of a few days. Explore Your Universe: Random APOD Generator
© Javier Zayaz