We now know a lot more about that cosmic body, and it looks like a snowman. Together they form Ultima Thule, a frozen world that is almost 4.5 billion miles from Earth, more distant than Pluto.
Scientists consider Ultima Thule an exquisite time machine that should provide clues to the origins of our solar system.
At that time the outer fringes of the solar system consisted of "innumerable small particles or pebbles", Moore explained, that slowly coalesced into larger ones.
NASA now expects New Horizons' mission in the Kuiper Belt to run through 2021 at least. The smaller one, which is 9 miles across, is "Thule". NASA hopes it will help to illuminate how planets were created four and a half billion years ago, both in our solar system and beyond.
It also comes with a visual that tells the story of the Ultima Thule project. Is it two icy objects orbiting each other, or a single "peanut"?
"The spacecraft is in peak health", said Stern.
This means we're truly seeing one of the first planetesimals, or objects, that went on to form planets.
"Ultima Thule"-a traditional name of distant places beyond the known world-was a "relatively common suggestion" among some 34,000 publicly nominated monikers, Newsweek's Meghan Bartels reported in March".
An earlier, fuzzier image made it look like a bowling pin.
"Meet #UltimaThule! What you're seeing is the 1st contact binary ever explored by a spacecraft", tweeted Nasa.
The scientists now say with confidence that Ultima Thule long ago was two bodies that got stuck together, what they call a "contact binary".
Moore said it appears the two spheres came together gently, at speeds of perhaps 1 or 2 miles per hour - not in some violent collision in space. "If you had a collision with another vehicle at those speeds, you may not even bother to fill out the insurance forms", he said.
On Wednesday, NASA officials said they "could not be happier" with the latest image of the "snowman", which it said were "separate objects now joined together".
Planetary scientists have never before seen a close-up of an object like Ultima Thule. "New Horizons has set a new bar for state-of-the-art spacecraft navigation".
It will take almost two years for New Horizons to beam back all of its observations of Ultima Thule. Many more photos are expected to be released soon.
Ultima Thule is situated in the Kuiper Belt, a distant region of the Solar System.
The colour variation shows just how dark the object is with the brightest areas reflecting just 13 per cent of the light falling on them. That's why it already holds such lessons about the formation of the planets.
Viewing MU69 is like looking at some of the "only remaining building blocks of the solar system" said Moore.
"This really puts the nail on the coffin now". Stern said the thing that was most surprising about the experience was "picking a Kuiper Belt object out of a hat" and then finding out that the team had picked a victor.
He added: 'It is going to revolutionise our knowledge of planetary science'.