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. January 2, 1997Explanation: What caused the bubbles and arcs in NGC 2359? The main suspect is the Wolf-Rayet star in the center of one of the bubbles - visible slightly below and to the right of the center of the above photograph. Most Wolf-Rayet stars are known to be massive, highly luminous stars that continually cast off material in a stellar wind - which commonly form bubbles in the interstellar medium. But the unusual structure of the NGC 2359 arcs indicate something more complex is going on. Is the star moving supersonically? Is there another energetic star in the vicinity? Future observations may give more pieces to this picturesque puzzle. Authors & editors:NASA Technical Rep.: Jay Norris. Specific rights apply. A service of: LHEA at NASA/ GSFC&: Michigan Tech. U.