Hubble finds new Neptune moon: NASA

Hubble finds new Neptune moon: NASA

U.S. space agency NASA said Monday its Hubble Space Telescope has found a new moon orbiting the distant blue-green planet Neptune, the 14th known to be circling the giant planet.

The moon, designated S/2004 N 1, is estimated to be no more than 12 miles (19 kilometers) across, making it the smallest known moon in the Neptunian system, NASA said.

It is so small and dim that it is roughly 100 million times fainter than the faintest star that can be seen with the naked eye, and it even escaped detection by NASA's Voyager 2 spacecraft, which flew past Neptune in 1989 and surveyed the planet's system of moons and rings, the agency said.

Mark Showalter of the U.S. nonprofit science research group SETI Institute found the moon on July 1, while studying the faint arcs, or segments of rings, around Neptune.

"The moons and arcs orbit very quickly, so we had to devise a way to follow their motion in order to bring out the details of the system," he said in a statement. "It's the same reason a sports photographer tracks a running athlete -- the athlete stays in focus, but the background blurs."

The method involved tracking the movement of a white dot that appears over and over again in more than 150 archival Neptune photographs taken by Hubble from 2004 to 2009.

Showalter noticed the white dot about 65,400 miles (one million kilometers) from Neptune located between the orbits of the Neptunian moons Larissa and Proteus. Showalter plotted a circular orbit for the moon, which completes one revolution around Neptune every 23 hours, NASA said.

海王星又添一颗小卫星

新华网华盛顿７月１５日电（记者林小春）美国航天局１５日宣布,"哈勃"太空望远镜发现了海王星的又一颗卫星.至此,海王星拥有的卫星数量上升至１４颗.

美国航天局当天发表声明说,这颗卫星直径不超过１９公里,是海王星所有卫星中最小的.它在距海王星约１０５万公里的圆形轨道上运转,周期为２３小时.它的亮度比我们从地球上肉眼能看到的最暗淡的星星还要弱一亿倍,以至于１９８９年"旅行者"２号探测器飞经海王星时,也没有发现它.

有趣的是,"哈勃"太空望远镜其实９年前就抓拍到它的踪影,但直到本月１日,美国科研组织"搜寻外星文明研究所"的马克·肖沃尔特在研究海王星的弧段数据时,才偶然发现它的存在.

在"哈勃"拍到的照片上,这颗卫星呈现为一个白点.进一步分析发现,２００４年至２００９年间,共有１５０多张"哈勃"拍摄的海王星照片上存在这个白点."谁都可能成为这颗卫星的发现者,"肖沃尔特说.