The first image (shown at top), was taken by the spacecraft's Long-Range Reconnaissance Imager (LORRI) at 05:01 UTC (01:01 EDT) on January 1st, 2019.
The first detailed images beamed back from the U.S. 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. Together they form Ultima Thule, a frozen world that is almost 4.5 billion miles from Earth, more distant than Pluto.
In addition to learning its true shape, New Horizons also captured color data when it made its close pass.
So far, scientists have learned that Ultima is red, with a rotational period of roughly 15 hours.
The main priorities for the research is mapping Ultima Thule's surface, as well as looking for any potential moons and rings.
NASA's New Horizons' team released the first close-up images from Ultima Thule on Wednesday afternoon. "Ultima Thule is the first object that will shed light on those earliest conditions".
The team says that the two spheres likely joined as early as 99 percent of the way back to the formation of the solar system, colliding no faster than two cars in a fender-bender.
New Horizons rocketed from Cape Canaveral, Florida in 2006.
It also looks pristine, nearly unchanged since it formed out of a disk of dust and gas that orbited the sun more than 4.5 billion years ago.
Scientists are keen to study Ultima Thule as it lives in a region that has been relatively untouched since the formation of the solar system, which in turn helps them better understand planetary formation.
Thule is estimated to be 9 miles (14 kilometers) across, while Ultima is thought to be 12 miles (19 kilometers). At left is an enhanced color image taken by the Multispectral Visible Imaging Camera (MVIC), produced by combining the near infrared, red and blue channels. Unlike comets and other objects that have been altered by the sun over time, Ultima Thule is in its pure, original state: It's been in the deep-freeze Kuiper Belt on the fringes of our solar system from the beginning.
More information continues to be downloaded, including topography, atmosphere, and composition of Ultima Thule.
Images also revealed that the two lobes have a mottled appearance.
Jeff Moore, New Horizons Geology and Geophysics team lead, said: "New Horizons is like a time machine, taking us back to the birth of the solar system".
As Helene Winters, New Horizons' Project Manager, indicated, it won't stop there.
New Horizons spent 13 years travelling to Ultima Thule's location at the heart of the Kuiper Belt.