艾达与艾卫: 小行星和它的卫星
Ida and Dactyl: Asteroid and Moon
Image Credit: NASA, JPL, Galileo Mission
Explanation: This asteroid has a moon. The robot spacecraft Galileo on route to Jupiter in 1993 encountered and photographed two asteroids during its long interplanetary voyage. The second minor planet it photographed, 243 Ida, was unexpectedly discovered to have a moon. The tiny moon, Dactyl, is only about 1.6 kilometers across and seen as a small dot on the right of the sharpened featured image. In contrast, the potato-shaped Ida is much larger, measuring about 60 kilometers long and 25 km wide. Dactyl is the first moon of an asteroid ever discovered — now many asteroids are known to have moons. The names Ida and Dactyl are from Greek mythology.
Tomorrow’s picture: sea blue sky
艾达与艾卫: 小行星和它的卫星
影像提供: NASA, JPL, Galileo Mission
说明: 这颗小行星竟然也有卫星。在前往木星的漫长行星际旅途里，伽利略号宇宙飞船于1993年二次遇见及拍摄小行星。它所拍摄的第二颗小行星艾达（243 Ida），意外的拥有自已的卫星。在这幅经过锐化的主题影像里，右侧的小白点，就是这颗宽约1.6公里的艾卫（载克太）。作为对比，马铃薯形的艾达，长约60公里，宽则在25公里左右。艾卫是我们发现的第一颗小行星之卫星，至今已发现许多拥有卫星的小行星。艾达和载克太都是希腊神话的人物。 （Ida 艾达；Dactyl 艾卫 载克太）
明日的图片: sea blue sky
