Next steps: The observation of the mysterious object comes 3.5 years after New Horizons gave us our best ever look at Pluto and 12 years since New Horizons launched from Cape Canaveral. At the time, Ultima Thule was at a distance of nearly 6.5 billion kilometres from the Sun, making this the most distant planetary flyby attempted, and the first time that a Solar System object of this type has been seen close-up, NASA said in a statement. The first fuzzy pictures of Ultima Thule show that it seems to be spinning and is about 22 miles long by 9 miles wide and shaped a bit like a peanut.
But despite the festive atmosphere - which included the release of a New Horizons song recorded by contributing scientist and rock guitarist Brian May of Queen, who was on hand for the event - the mission team had no way of knowing if their spacecraft was still in one piece and executing its reconnaissance of Ultima Thule.
Ultima Thule is the first destination to be reached that was not even known until after the spacecraft's launch.
The object Ultima Thule, the nickname for 2014 MU69, was discovered by Marc Buie of Southwest Research Institute in 2014, in an extraordinary search among millions of stars imaged for the objective with the Hubble Space Telescope.
As revellers watched fireworks exploding in the night sky, billions of kilometres beyond the spectacle, NASA's New Horizons probe quietly notched up another fantastic first - making its closest approach to the most distant object ever visited by a spacecraft.
But Alan Stern, a planetary scientist from the Southwest Research Institute who is principal investigator for the $800 million mission, which explored Pluto in 2015, said he was confident.More news: Protests in India after Women Enter Hindu Temple
The night before, after ringing in the new year, team members had counted down and celebrated the moment they expected New Horizons would make its closest approach to its target based on their knowledge of its trajectory. However, this still won't be the end of its mission, as NASA hopes that it will continue to explore the distant Edgeworth-Kuiper Belt until at least 2021. Scientists hope to learn about those origins through New Horizons' observations deep inside the so-called Kuiper Belt, or frozen Twilight Zone, on the fringes of the solar system. Confirmation won't come for hours, though, given the vast distance. "From here out the data will just get better and better!" Its extended mission then set its sights on a new object further into the Kuiper Belt.
"Reaching Ultima Thule from 4 billion miles away is an incredible achievement", Adam Hamilton, president and CEO of the Southwest Research Institute, said in the statement. So they won't know until late morning whether the spacecraft survived.
LAUREL, MARYLAND-Cheers erupted just after 10:30 AM Eastern this morning in a small control room at the Johns Hopkins University Applied Physics Laboratory (APL) here. The spacecraft zoomed within 2,200 miles (3,500 kilometres) of it, more than three times closer than the Pluto flyby.
Another question would be to see if Ultima is actually a single object or two objects orbiting each other.
Ultima Thule orbits a billion miles beyond Pluto and has been locked in a state of deep-freeze preservation since the universe began some 4.5 billion years ago. It's fitting, considering New Horizons' pioneering journey.
This flyby is the first exploration of a small Kuiper Belt object up close - and the most primitive world ever observed by a spacecraft.