Andromeda Galaxy

The Andromeda Galaxy, M31, is the nearest major galaxy to our own Milky Way. It is about 780 kiloparsecs or 2.5 million light years away, as measured by it's brightest Cepheid variable stars. It is rather similar to our own galaxy in structure. It shows spiral arms, a bulging central disc and is about 80 kiloparsecs or 260,000 light years across the entire galaxy. The individual stars in the image are foreground stars in our own galaxy.

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This is an ultraviolet image of Andromeda from NASA's Galaxy Evolution Explorer. Image credit: Galex, NASA/JPL-Caltech

A very different view of the Andromeda Galaxy is this infrared view taken by NASA's Spitzer Space Telescope . It revealed a never-before-seen dust ring deep within the Andromeda galaxy. Combined with previous data about an outer ring, it was interpreted as evidence that the neighboring dwarf galaxy M32 collided with the Andromeda Galaxy about 210 million years ago, plunging through its central disc. 这张由NASA的斯皮策太空望远镜拍摄的红外图像提供了关于仙女座星系完全不同的视角。它揭示了仙女座星系内部一个前所未见的尘埃环。结合之前关于外环的数据，这一发现被解释为邻近矮星系M32约210 million years ago与仙女座星系发生碰撞的证据，碰撞过程中M32穿透了仙女座星系的中心盘。

blue 135-175 nm 蓝色 135-175 nm green 175-280 nm 绿光 175-280 纳米 red 24 microns (24000 nm) 红光 24 微米（24000 纳米）

This false color image shows the differences in the appearance of the Andromeda Galaxy at different wavelengths. The blue and green images were actually taken in the ultraviolet by the Galaxy Evolution Explorer in 2003. The red image is actually taken in the infrared by the MIPS instrument. They list the distance as 780 kpc. The image credit is NASA/JPL-Caltech/K. Gordon (Univ. of Ariz.) & GALEX Science