The first detailed images beamed back from the United States agency's New Horizons mission allowed scientists to confidently determine the body was formed when two spheres, or "lobes", slowly gravitated towards each other until they stuck together - a major scientific discovery. The mission team named the larger object "Ultima" and the smaller one "Thule".
Since the first approach photographs were released (which were pixilated and blurry), the New Horizons team has released new images from the spacecraft that show Ultimate Thule in color and greater detail.
The Kuiper Belt is the edge of our solar system, part of the original disk from which the sun and planets formed.
What has got scientists all a-quiver is that the appearance of Ultima Thule seems to confirm theories of planetary accretion, which has specks of dust colliding to form objects with sufficient gravity to attract each other. By contrast, he suggested, scientists did not know for sure whether other two-lobe bodies - most notably the rubber ducky-like Comet 67P/Churyumov-Gerasimenko - were two objects that came together or one larger body that had eroded into its current shape.
It's a moment that could define the future, but the name "Ultima Thule" is one from the past.
Scientists said there were no obvious impact craters in the latest photos but a few apparent "divots" and suggestions of hills and ridges.
However, more will be revealed as more data comes in. "New Horizons has set a new bar for state-of-the-art spacecraft navigation", said Stern.
Moore believes MU69 is composed of small icy bodies that are about 4.5 billion years old.
Meanwhile, it must be said that New Horizons, indeed, is living up to its name.
One leading theory is that of pebble accretion, which posits that bits of raw planetary material of all shapes and sizes glommed onto each other until they became singular, gargantuan units.
"This is the first object we can clearly tell was born this way, and didn't evolve to look this way", Stern said.
"It's actually gratifying to see these nearly perfectly formed contact binaries in their native habitats", said Jeffrey M. Moore, leader of the mission's geology and geophysics team.
Ultima's current rotation rate, estimated at about 15 hours for a complete turn, isn't fast enough to fling the two balls apart, Moore said. That color can be explained by irradiation of ices on its surface, said Carly Howett of the Southwest Research Institute.
The brightest areas on the surface of Ultima Thule reflect only about 13% of the sunlight that reaches it - an incredibly small amount, given that it's 6.4 billion kilometres from the sun. This created a snowman-shaped, two-lobed binary object.