April 9, 1999
The Moon has changed phase thousands of times since the beginning of the cosmos, but only once did it shine on the night you arrived.
WR 104: Pinwheel Star
Birthday · April 9, 1999
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APOD published April 9, 1999. Full image credits are on the original APOD entry below. A publication-date match, not a photo taken on your date. Independent of NASA.
Like a cosmic lawn sprinkler, dust streaming from a rotating star system creates a pinwheel pattern in this false color infrared image. Astronomers discovered the surprising star dust scenario using a sophisticated interferometer and the 10 meter Keck I telescope to observe the bright Wolf-Rayet star WR 104. Wolf-Rayet stars are thought to be massive objects on the brink of a cataclysmic supernova explosion - having grown so hot and bright that their intense light begins to drive material away in a stellar wind. The problem is, their starlight would also be so intense that any dust flakes should be destroyed! A possible solution to this dusty dilemma is that a companion star exists hidden in the bright central region, generating wind interactions which shield a relatively narrow dust forming region from the light of WR 104. As the binary system rotates, the spray of surviving dust particles appears to spiral outward.