Moon Over Andromeda
影像版權與提供: Adam Block and Tim Puckett
Explanation:
The Great Spiral Galaxy in Andromeda (aka M31), a mere 2.5 million light-years distant, is the closest large spiral to our own Milky Way. Andromeda is visible to the unaided eye as a small, faint, fuzzy patch, but because its surface brightness is so low, casual skygazers can't appreciate the galaxy's impressive extent in planet Earth's sky. This entertaining composite image compares the angular size of the nearby galaxy to a brighter, more familiar celestial sight. In it, a deep exposure of Andromeda, tracing beautiful blue star clusters in spiral arms far beyond the bright yellow core, is combined with a typical view of a nearly full Moon. Shown at the same angular scale, the Moon covers about 1/2 degree on the sky, while the galaxy is clearly several times that size. The deep Andromeda exposure also includes two bright satellite galaxies, M32 and M110 (bottom).
說明:
離我們只有250萬光年遠的仙女座大星系 (又稱為M31),，是離我們銀河系最近的大型螺旋星系。仙女座大星系在人類肉眼中，是一個昏暗、瀰漫的小斑塊，因為它的表面亮度極低，一般的觀星人感受不到它在地球天空中應是一個很壯觀的天體。這幅有趣的組合影像，用我們較熟悉也較亮的月亮來呈現這個鄰近星系的視張角之大小。在這幅仙女座大星系的深場影像裡，可見到鑲在從亮黃色星系核向外伸展的漩渦臂之美麗藍色星團，以及特別嵌入的一輪明月。在相同的視張角尺標下，月亮大約涵蓋半度的天區，而很明顯的，視覺上仙女座大星系要比月亮大上數倍。在這幅仙女座大星系的深場影像裡，還可以見到二個明亮的衛星星系；中上方的M32和左下角的M110。
資料來源: Scientific American
Department of Physics, NCKU
