Explanation:
The image displays stars, dust, and nebulae in NGC 6559.
The center of the NGC 6559 nebula is crowded with bright stars and dark interstellar gas, permeated by a diffuse red glow primarily composed of hydrogen. High-energy light emitted from neighboring stars ionizes the interstellar hydrogen; when protons subsequently recombine with electrons, they emit light of specific colors, including the red luster seen here. Small dust particles efficiently reflect blue starlight, forming the blue reflection nebulae near the two bright stars. Simultaneously, the dust absorbs visible light, creating the dark clouds and filaments observed. NGC 6559 is located in the direction of the constellation Sagittarius, approximately 5,000 light-years away from us.
NASA Website: http://antwrp.gsfc.nasa.gov/apod/astropix.html
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