It is by far the most distant world a spacecraft - and by extension humanity - has ever explored.
"You can see they're clearly two separate objects that have come together", said Cathy Olkin, the mission's deputy project scientist.
At about four billion miles from Earth in the Kuiper Belt, spacecraft New Horizons captured the never seen before close-up images of Ultima Thule, an icy celestial object about 20 miles long. In 2015, the spacecraft passed Pluto, providing the first images of a world once considered our ninth planet.
If the craft holds up, and the support mission back on Earth gets funding for a "hyperextended mission", New Horizons could be sampling the interstellar medium by the time today's newborns are finishing high school. Brian May, the lead guitarist of Queen, who also is an astrophysicist, released a new single commemorating the event - it is called, fittingly, "New Horizons" - just after midnight Monday.
"Human beings are born, we change over time, and, eventually we die", says Jason Kalirai, civil space mission area executive at the Johns Hopkins University Applied Physics Laboratory.
"This mission's always been about delayed gratification", Stern reminded reporters.
"Reaching Ultima Thule from 4 billion miles away is an incredible achievement". Signals confirming the spacecraft had survived the encounter and had filled its digital recorders with science data on Ultima Thule reached the mission operations centre at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland nearly exactly 10 hours later, Earth Sky reported.
"New Horizons is like a time machine, taking us back to the birth of the solar system", Moore said.
Scientists believe that around 4.5 billion years ago, just millions of years after the formation of the solar system, dust and pebbles clumped together to form the object's two lobes - Ultima and Thule.
Light travel time back to the Earth was expected to be some six hours as we await the images that will hopefully be coming in from this distant remnant of the creation of the solar system!
Early images show that Ultima Thule is about 31 kilometers by 19 kilometers. It appears not to have any impact craters. An earlier colour image, taken by the Multispectral Visible Imaging Camera (MVC), shows a reddish surface, that, rather than NASA's snowman assertion, put us in mind of South Park's Mr Hankey. The lobes, he said, were really only "resting on each other".
These images, though, are not of that absolute closest approach.
As the probe flies 2,200 miles (3,540 km) above Thule's surface, scientists hope it will detect the chemical composition of its atmosphere and terrain in what NASA says will be the closest observation of a body so remote.
It will take almost two years for New Horizons to beam back all of its observations of Ultima Thule.