Astronomy Picture of the Day—20190221

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2019 February 21

TheUmbra of Earth

ImageCredit & Copyright: Antonio Finazzi

Explanation:The dark, inner shadow of planet Earth is called the umbra. Shaped like a coneextending into space, it has a circular cross section most easily seen during alunar eclipse. For example, on January 21 the Full Moon slid across thenorthern half of Earth's umbral shadow, entertaining moonwatchers around muchof the planet. In the total phase of the eclipse, the Moon was completelywithin the umbra for 63 minutes. Recorded under clear, dark skies from thehills near Chiuduno, Italy this composite eclipse image uses successivepictures from totality (center) and partial phases to trace out a large part ofthe umbra's curved edge. Reflecting sunlight scattered by the atmosphere intoEarth's shadow, the lunar surface appears reddened during totality. But closeto the umbra's edge, the limb of the eclipsed Moon shows a distinct blue hue.The blue eclipsed moonlight originates as rays of sunlight pass through layershigh in the upper stratosphere, colored by ozone that scatters red light andtransmits blue.

地球的本影

解释：地球黑暗的内影被称为本影，其形状像一个延伸进入空间的圆锥，具有圆形截面，在月食期间最容易看到。1月21日，满月划过地球本影的北半部，娱乐了地球上众多的月球观测者。在食甚阶段，月亮完全处于本影中的时间长达63分钟。这幅合成的月食影像摄于意大利丘杜诺附近的小山丘，利用连续的从食甚（中心）到偏食相的照片，追踪出本影的弯曲边缘的大部分。由于大气层的散射作用，月表在食甚期间显得发红。但在接近本影的边缘，被食的月亮边缘显示出独特的蓝色光晕，这一蓝光起源于当光线通过上平流层高处时，被散射红光的臭氧染色，转变为蓝色。