2nd LD Writethru: New Horizons' Pluto flyby makes history

NASA's New Horizons performed the first-ever flyby of Pluto on Tuesday, about 12,472 kilometers (7,750 miles) above the surface, making the closest approach to the dwarf planet at 7:49 a.m. EDT (1149 GMT).

"Hello Pluto! We' re at closest approach. Congrats to all!" said the mission team on New Horizons's Twitter account.

To celebrate, U.S. space agency NASA unveiled a "love note" from Pluto, showing a reddish world with a stunning heart-shaped feature on its face, which is the last and most detailed image of the dwarf planet sent to Earth before the moment of closest approach.

At a press briefing after the encounter, the mission's principal investigator Alan Stern revealed some extremely preliminary first science results from the New Horizons' Pluto flyby and joked that he' s secretly been working on a Pluto lander.

The spacecraft currently is in data-gathering mode and not in contact with flight controllers at the Johns Hopkins University Applied Physical Laboratory (APL), the U.S. space agency NASA said in a statement.

Scientists are waiting to find out whether New Horizons "phones home," transmitting to Earth a series of status updates that indicate the spacecraft survived the flyby and is in good health.

"We will breathe the final sigh of relief at 9 p.m. and that is when we can call it a successful flyby," said Stern.

A small batch of images is expected to be released later. After a voyage of nine and half years, the probe is more than 4.77 billion km away, where radio signals, even traveling at light speed, need 4.5 hours to reach Earth. Round trip communication between the spacecraft and its operators requires about nine hours.

It's the first mission to Pluto and its five moons. After Tuesday's encounter, all nine of the solar system's originally recognized planets have now been visited by a spacecraft. Pluto is now the most distant object ever visited by humanity.

"The exploration of Pluto and its moons by New Horizons represents the capstone event to 50 years of planetary exploration by NASA and the United States," said NASA Administrator Charles Bolden.

The unmanned, piano-sized probe, which was launched in 2006, has traveled more than 5 .2 billion kilometers to reach Pluto. But the probe won't orbit nor land on Pluto. Instead, it will keep flying, heading its journey deeper into the Kuiper Belt, a region that scientists think is filled with hundreds of small, icy objects. Scientists believe that Kuiper Belt objects, such as Pluto, preserve evidence about the early formation of the solar system.

The dwarf planet, formerly known as planet Pluto, was kicked out of the planet group in the solar system in 2006 by the International Astronomical Union (IAU) under a new universal definition of a planet. Endi