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.