Glossary term: 北极星
Description: 北极星是距离北天极最近的亮星(1度以内)。它的正式名称是小熊座α星,通常被称为北极星,在中国也叫勾陈一、北辰、宸极。北天球的所有恒星都似乎围绕着它旋转,因此它是进行导航和天体测量的绝佳固定点。它的地平高度可以提供观测地点的大致纬度。不过,由于地球自转轴的进动,北极星在天球上的位置正在慢慢发生变化,因此再过几个世纪,北极星就不再能指示北天极的位置了。
北极星是一个由三合星系统。主星是一颗黄超巨星,被命名为北极星Aa;伴星是一颗较小的主序星,被命名为北极星Ab。它们在非常近的轨道上相互绕转运行。这对恒星还有一颗较大的伴星——北极星B,它是一颗主序星,在2400个天文单位的距离上运行,轨道周期约为29.3年。北极星B可以用普通望远镜分辨出来。哈勃太空望远镜能够分辨出北极星三合星系统的所有三个成员。北极星的视星等会有波动,这是因为北极星Aa是一个仙王座变星。北极星系统距离地球约447光年。
Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher The translation of this term and its definition is still awaiting approval
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