人类可以第一次近距离观察冥王星。
美国国家航空航天局（NASA）的新地平线（New Horizons）太空探测器 以高于以往任何太空探测器的速度飞行了近十年，完成了飞越冥王星的任务。
新地平线太空探测器携带了1930年发现冥王星的天文学家克莱尔·汤博（Clyde Tombaugh）的一部份骨灰，此外还有一张记载了400,000个地球人姓名的光盘。这些人参加NASA在新地平线太空探测器升空前发起的“向冥王星发送姓名”的活动。
飞行控制室鼓掌庆贺新地平线太空探测器抵达冥王星。(JHUAPL/NASA)
新地平线太空探测器正向地球传送有关冥王星的重要数据。目前科学家已经有了很多新的发现：
冥王星的直径接近2,400公里，可确认是海王星（Neptune）轨道外已知太阳系天体中最大的一个。以往的数据只属于估算。
相对天体的规模，冥王星的卫星卡戎（Charon）是太阳系最大的卫星。
图像显示以往从未发现的特征，包括广大的心形平原。
冥王星敞开胸怀欢迎新地平线太空探测器。 (JHUAPL/NASA)
新地平线太空探测器在进入星球系统以外的柯伊伯带（Kuiper Bel）之际，将遇到冰状团块，有些大如矮行星。据说这些神秘莫测的团块保存了太阳系早期形成阶段的证据。
多年来，科学家曾认为冥王星是太阳系第9大行星。2006年，科学家修改了原来的星球评级，认为冥王星属于矮行星，是柯伊伯带的众多天体之一。
Pluto: Ready for its close-up
Humanity just got its first close-up view of Pluto.
Traveling faster than any previous spacecraft, it took nearly a decade for NASA’s New Horizons spacecraft to get there.
New Horizons carries cremated ashes of Clyde Tombaugh, the astronomer who discovered Pluto in 1930. A CD-ROM on board includes the names of more than 400,000 people who accepted NASA’s pre-launch offer to “send your name to Pluto.”
The control room celebrates as New Horizons reaches Pluto. (JHUAPL/NASA)
New Horizon is sending home important data about Pluto. Scientists already have learned a lot:
Pluto is less than 2,400 kilometers in diameter. That makes it the largest object in our solar system beyond the orbit of Neptune. (Previous measurements were only estimates.)
Pluto’s moon Charon is the solar system’s largest moon relative to its planet.
Photos disclose previously unseen features, including a vast, heart-shaped plain.
Pluto welcomes New Horizons with an open heart. (JHUAPL/NASA)
As New Horizons enters the Kuiper Belt, a solar system region beyond the planets, it will encounter icy objects, some as large as dwarf planets. These mysterious objects are thought to preserve evidence about the early formation of the solar system.
For many years, scientists considered Pluto our solar system’s ninth planet. In 2006, they downgraded it to “dwarf planet,” one of many celestial objects in the Kuiper Belt.
