冰岛瀑布上空的绚丽极光

探索宇宙（universe）！每天都会展示一张我们迷人宇宙的不同图像或照片，并附上一段由专业天文学家（astronomer）撰写的简短解释。

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.

解释：当夜天（night sky）中充满了色彩，仿佛倾泻在冰岛的Skógafoss瀑布之上时，那是何等壮观的景象。这张照片由摄影师在2025年4月通过单次5秒曝光拍摄而成。观赏极光（Aurora）是许多人的愿望清单之一，但这并不容易。它需要高太阳活动（solar activity）、黑暗且晴朗的天空，通常还需要在高纬度（high latitude）地区进行观测。这使得北极光（northern light）比相应的南极光（southern light）更容易被观测到，原因很简单，南半球（southern hemisphere）的陆地面积较少，尤其是在南极圈（antarctic circle）附近。极光是由来自太阳风（solar wind）的荷电粒子（charged particle）引起的，这些粒子被地球（Earth）的磁层捕获，并被磁场（magnetic field）引导至靠近两极的区域，在那里它们与大气中的气体粒子发生碰撞。不同的颜色表明了在不同高度与不同气体的相互作用，例如氧气（红色和绿色）以及氮气（蓝色和粉色）。

Explanation: What a sight to behold, when a night sky became filled with colors that appeared to rain over the Skógafoss waterfall in Iceland. This image was taken in a single 5 second exposure by the photographer in April 2025. Seeing an aurora is on many people's bucket lists. But it is not easy. It requires high solar activity, dark and clear skies, and usually a viewing location at high latitude. That makes the northern lights more easily seen than the corresponding southern lights, simply because there is less landmass in the Southern Hemisphere, especially around the Antarctic Circle. Auroras are caused by charged particles from the solar wind that are captured by the Earth's magnetosphere and guided by the magnetic field to a region close to one of the poles, where they collide with gas particles in the atmosphere. Different colors indicate interactions with different gases at different altitudes, like oxygen (red and green) and nitrogen (blue and pink).