After analyzing these new images, scientists say the larger lobe more closely resembles a large pancake, and the smaller lobe looks a bit like a walnut.
NASA's NewHorizons flew past Ultima Thule, an object located in a region of primordial objects 1 billion miles past Pluto.
"We've never seen something like this orbiting the sun", Alan Stern, principal investigator on the New Horizons mission, said in a press release.
Now that scientists have downloaded more data from the distant spacecraft, however, our view of Ultima Thule has changed.
At 4 billion miles from Earth, MU69 (also nicknamed Ultima Thule) is the farthest-away object a human spacecraft has ever visited.
A sequence of images captured as New Horizons moved away from the object in the Kuiper Belt at a velocity of 50,000 km/hour, taken about 10 minutes after closest approach, show a much flatter appearance.
At left is a composite of two images taken by New Horizons' high-resolution Long-Range Reconnaissance Imager (LORRI), which provides the best indication of Ultima Thule's size and shape so far.
The first close-up images of Ultima Thule - with its two distinct and, apparently, spherical segments - had observers calling it a "snowman".
'But more importantly, the new images are creating scientific puzzles about how such an object could even be formed. A relatively long exposure time was used to maximise the camera's signal level at the expense of some blurring of the KBO's crescent.
"The shape model we have derived from all of the existing Ultima Thule imagery is remarkably consistent with what we have learned from the new crescent images", said Simon Porter, a New Horizons co-investigator from the Southwest Research Institute.
New Horizons then set out an extended mission, which centered on a close flyby of Ultima Thule, which is officially known as 2014 MU69. By noting which of these stars went dark as Ultima blocked them out, mission scientists were able to map out the object's (surprisingly flat) shape.
The departure pictures were taken from an unexpected point in comparison to the methodology photographs and uncover integral data on Ultima Thule's shape. The focal edge of the grouping was gone up against January 1 at 05:42:42 UT (12:42 a.m. EST), when New Horizons was 5,494 miles (8,862 kilometers) past Ultima Thule, and 4.1 billion miles (6.6 billion kilometers) from Earth.
"While the very nature of a fast flyby in some ways limits how well we can determine the true shape of Ultima Thule, the new results clearly show that Ultima and Thule are much flatter than originally believed, and much flatter than expected", added Hal Weaver, New Horizons project scientist from the Johns Hopkins Applied Physics Laboratory. "This will undoubtedly motivate new theories of planetesimal formation in the early solar system".