A NASA craft has is believed to have reached the solar system's outermost region early Tuesday morning, flying close to a space rock 20 miles long and billions of miles from Earth on a mission to gather clues about the creation of the solar system.
The body is farther from Earth than any other that has had such a close encounter with a NASA probe, scientists believe.
The New Horizons probe was slated to reach the 'third zone' in the uncharted heart of the Kuiper Belt at 12:33 a.m. Eastern.
Scientists will not have confirmation of its successful arrival until the probe communicates its whereabouts through NASA's Deep Space Network at 10:28 a.m. Eastern, about 10 hours later.
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NASA's New Horizons spacecraft flew past the mysterious object at 12:33 a.m. Tuesday. The latest images of the object reveal an elongated shape
Once it enters the peripheral layer of the belt, containing icy bodies and leftover fragments from the solar system's creation, the probe will get its first close-up glance of Ultima Thule, a cool mass shaped like a giant peanut, using seven on-board instruments.
Nasa tweeted after the flyby that confirmation of the signal from the spacecraft will be made public at 9.45am
The first image of Ultima Thule's shape was taken during the spacecraft's approach but clearer pictures are not expected for some time as it can take several hours for radio signals to reach Earth from that far away.
Flight controllers said everything looked good for New Horizons' flyby of the tiny, icy object nicknamed Ultima Thule at 12:33 a.m. on Tuesday.
The mysterious, ancient target is 4 billion miles (6.4 billion kilometers) from Earth and is in the Kuiper Belt.
Scientists wanted New Horizons observing Ultima Thule during the encounter, not phoning home. So they had to wait until late morning before learning whether the spacecraft survived.
The green segment of the line shows where New Horizons has traveled since launch while the red indicates the spacecraft's future path
With New Horizons on autopilot, Mission Control was empty at Johns Hopkins University's Applied Physics Laboratory in Laurel, Maryland. Instead, hundreds of team members and their guests gathered nearby on campus for back-to-back countdowns.
The crowd ushered in 2019 at midnight, then cheered, blew party horns and jubilantly waved small U.S. flags again 33 minutes later, the appointed time for New Horizons' closest approach to Ultima Thule.
A few black-and-white pictures of Ultima Thule might be available following Tuesday's official confirmation, but the highly anticipated close-ups won't be ready until Wednesday or Thursday, in color, it is hoped.
'We set a record. Never before has a spacecraft explored anything so far away,' said the project's lead scientist who led the countdown to the close encounter, Alan Stern of Southwest Research Institute. 'Think of it. We're a billion miles farther than Pluto.'
New Horizons principal investigator Alan Stern (C) of the Southwest Research Institute (SwRI), Boulder, CO, celebrating with school children at the exact moment that the New Horizons spacecraft made the closest approach of Kuiper Belt object Ultima Thule on Tuesday, January 1
Stern called it an auspicious beginning to 2019, which will mark the 50th anniversary of Neil Armstrong and Buzz Aldrin's footsteps on the moon in July 1969. People celebrate above
A handout photo made available by NASA shows New Horizons principal investigator Alan Stern (4-R), New Horizons project manager Helene Winters (3-R), Fred Pelletier (2-R), lead of the project navigation team and New Horizons co-investigator John Spencer (R) attending a press conference prior to the flyby of Ultima Thule by the New Horizons spacecraft, in Laurel, Maryland
Stern called it an auspicious beginning to 2019, which will mark the 50th anniversary of Neil Armstrong and Buzz Aldrin's footsteps on the moon in July 1969.
'Ultima Thule is 17,000 times as far away as the 'giant leap' of Apollo's lunar missions,' Stern noted in an opinion piece in The New York Times.
New Horizons, which is the size of a baby grand piano and part of an $800 million mission, was expected to hurtle to within 2,200 miles (3,500 kilometers) of Ultima Thule, considerably closer than the Pluto encounter of 2015.
Its seven science instruments were to continue collecting data for four hours after the flyby. Then the spacecraft was to turn briefly toward Earth to transmit word of its success. It takes over six hours for radio signals to reach Earth from that far away.
Scientists believe there should be no rings or moons around Ultima Thule that might endanger New Horizons. Traveling at 31,500 mph (50,700 kph), the spacecraft could easily be knocked out by a rice-size particle. It's a tougher encounter than at Pluto because of the distance and the considerable unknowns, and because the spacecraft is older now.
The flyby was fast, at a speed of nine miles (14 kilometers) per second. Seven