NASA's New Horizons probe flew by Pluto on July 14, capturing history's first up-close looks at the far-flung world. Closest approach was at 7:49 a.m. EDT (1149 GMT), when the spacecraft whizzed within 7,800 miles (12,500 kilometers) of Pluto's frigid surface. To celebrate, NASA unveiled the latest photo of Pluto, showing a reddish world with a stunning heart-shaped feature on its face.

After this close encounter, all nine of the solar system's traditionally recognized planets have now been visited by a robotic spacecraft — a massive undertaking begun in 1962 when NASA's Mariner 2 probe zoomed past Venus. More than 1,200 scientists, NASA guests and dignitaries - including 200 reporters - watched the flyby live at New Horizons' mission control center at Johns Hopkins University Applied Physics Laboratory in Laurel, Md. They chanted a countdown to the closest approach, then cheered and waved American flags as the big moment occurred. [New Horizons' Epic Pluto Flyby: Complete Coverage]

New Horizons is "a capstone mission," Glen Fountain, mission project manager from the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, told Space.com. "It is the completion of this initial reconnaissance of our solar system. It's giving us a new perspective about how we as human beings fit into the universe."

In a coincidence of cosmic proportions, today's close approach fell on the 50th anniversary of the first flyby of Mars, which NASA's Mariner 4 spacecraft executed on July 14, 1965.

"You couldn't have written a script that was better," New Horizons principal investigator Alan Stern, of the Southwest Research Institute in Boulder, Colorado, told Space.com.

There are no longer nine officially recognized planets, of course. The International Astronomical Union famously reclassified Pluto as a "dwarf planet" in 2006, in a decision that remains controversial today.

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