星系壁纸
by Left: Adolf Schaller for STScI; Right: Hubble Legacy Archive, NASA, ESA; Processing: Judy Schmidt
NASA Image Library · 公有领域（Public Domain）
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Our sky is filled with a diffuse background glow, known as the cosmic infrared background. Much of the light is from galaxies we know about, but previous Spitzer measurements have shown an extra component of unknown origin.
