撒哈拉沙漠上空的仙女星系

2022年7月11日

Andromeda over the Sahara Desert
Credit & Copyright: Jordi Coy

Explanation: What is the oldest thing you can see? At 2.5 million light years distant, the answer for the unaided eye is the Andromeda galaxy, because its photons are 2.5 million years old when they reach you. Most other apparent denizens of the night sky — stars, clusters, and nebulae — appear as they were only a few hundred to a few thousand years ago, as they lie well within our own Milky Way Galaxy. Given its distance, light from Andromeda is likely also the farthest object that you can see. Also known as M31, the Andromeda Galaxy dominates the center of the featured zoomed image, taken from the Sahara Desert in Morocco last month. The featured image is a combination of three background and one foreground exposure — all taken with the same camera and from the same location and on the same calendar day — with the foreground image taken during the evening blue hour. M110, a satellite galaxy of Andromenda is visible just above and to the left of M31’s core. As cool as it may be to see this neighboring galaxy to our Milky Way with your own eyes, long duration camera exposures can pick up many faint and breathtaking details. Recent data indicates that our Milky Way Galaxy will collide and combine with the similarly-sized Andromeda galaxy in a few billion years.

Tomorrow’s picture: noctilucent tower

撒哈拉沙漠上空的仙女星系
影像提供与版权: Jordi Coy

说明: 你能看到的最古老“物体”是什么？以肉眼可见为限的话，答案是2百50万光年远的仙女星系，因为来自它的光要经过2百50万年才能传到你的眼睛里。其他夜空中可见的天体，诸如恒星、星团和星云，距离通常介于数百到数千光年之间，因此近在我们银河系之内。以距离来论仙女星系也是你能见到最远的“物体”。在这幅上个月摄于摩洛哥的撒哈拉沙漠的主题影像里，亦名为M31的仙女星系，是中心处经过放大的特写天体。这幅影像组合了3张背景和1张前景照片，它们都是由同一部相机于同一个历日在同一地点所拍摄，背景照片则是摄于蓝色时段。其中，仙女星系的伴星系M110，位在M31核心的左上方。能以肉眼见到我们银河系的近邻或许很酷，不过长曝光影相机影像，更能呈现许多暗淡却令人屏息的细节。近来的观测数据指出，我们的银河系和大小相近的仙女星系，在数十亿年之内就会撞在一起并合而为一。

明日的图片: noctilucent tower