The images of Ultima Thule were captured by NASA's New Horizon spacecraft - and show the object is formed of two spheres, combined into one.
"Last night, overnght, the United States spacecraft New Horizons conducted the farthest exploration in the history of humankind, and did so spectacularly", New Horizons principal investigator Alan Stern told a news conference at the Johns Hopkins facility in Laurel, Maryland.
NASA is also interested in getting a closer look at the "neck" region of Ultima Thule, which appears much lighter in color than the rest of the surface.
The pictures released Wednesday were taken about an hour before New Horizons made its closest approach to Ultima Thule, when the spacecraft had the sun behind it and its target in front.
The new images show Ultima to be a contact binary, consisting of two separate masses that became stuck together.
Ultima Thule in colour.
Several factors make Ultima Thule, and the domain in which it moves, so interesting to scientists.
"We think what we are looking at is perhaps the most primitive object that has yet been seen by any spacecraft", Moore says, "and may represent a class of objects which are the oldest and most primitive objects that can be seen anywhere in the present solar system".
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Jeff Moore, the mission's team lead for geology and geophysics, likened New Horizons to a time machine, taking scientists back to the birth of the solar system.
Launched in January 2006, New Horizons embarked on its 4 billion-mile journey toward the solar system's edge to study the dwarf planet Pluto and its five moons.
Early analysis from New Horizons' camera suggests that Ultima Thule, based in the Kuiper Belt beyond Pluto, is the result of two bodies that are now fused together. While Earth anxiously sucks in a deep breath of anticipation, scientists have finally determined the color of Ultima Thule.
About ten hours ago, NASA shared a picture of the snowman-shaped Ultima Thule on Twitter. It is more than a billion kilometres past Pluto, and 6.4 billion kilometres from Earth.
"This is exactly what we need to move the modeling work on planetary formation forward", said Cathy Olkin, the mission's deputy project scientist.
"Let me say, that bowling pin is gone".
He added: "It is going to revolutionise our knowledge of planetary science". "The data we have look fantastic and we're already learning about Ultima from up close".
NASA researchers promised fresh announcements would drop Thursday, including on the composition and atmosphere of Ultima Thule, as new images with even more precise resolution have come through.