The first image of the object was an indistinct blur, but a NASA press conference on Wednesday gave us our best views yet, including a processed image showing Ultima Thule in a glorious reddish color.
The nature of New Horizons' mission provided NASA with a unique opportunity to explore more of the outer solar system after the 2015 main event.
May says the project "epitomises the human spirit's unceasing desire to understand the universe we inhabit" and adds: "Everyone who has devoted so much energy to this mission since its launch in January 2006 will be feeling they are actually inside that small but intrepid vehicle as it pulls off another spectacular close encounter". It's not totally clear how these shapes form, but it's thought that they begin as two objects orbiting one another that merge.
On Tuesday, based on early, fuzzy images taken the day before, scientists said Ultima Thule resembled a bowling pin.
Just such a nickname - Ultima Thule (pronounced TOOL-ie), for New Horizons' recent flyby target, 2014 MU69 - stirred controversy on Twitter late last night and early today (Jan. 1 and 2). Though it appeared to be bowling pin-shaped, its actual structure has remained hazy until now. Note the reduced red coloring at the neck of the object. Stern said the New Horizons team would start writing scientific papers next week, based on the data already in hand, and nearly certainly propose another mission extension to NASA by 2020.
This three-panel drawing depicts the likely scenario for how 2014 MU69 formed, as two different, gravitationally-bound objects formed from solar system debris, and then slowly spiraled in to eventually touch.
Scientists had suspected that Ultima Thule would not be perfectly round since the summer of 2017, when a global network of observers found the rock passing in front of a distant star.More news: Netflix announces premiere date for Stranger Things season 3
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Scientists have ascertained that the object takes about 15 hours to make a full rotation. The center is a higher-resolution image.
But even as the researchers celebrated their triumph of celestial navigation, the mission drew unwanted attention for the name Ultima Thule.
"This thing was born somewhere between 99 percent and 99.9 percent of the way back to T-zero (liftoff) in our solar system, really awesome", Stern said. By their estimates, this would have happened about 4.45 billion years ago, or 50 million years after the Solar System formed.
"So stay tuned", Jeff Moore, the New Horizons geology team lead, said on Wednesday. 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.
It is by far the most distant world a spacecraft - and by extension humanity - has ever explored.
Future images sent back to earth will be of a higher quality as they will have been taken closer to the object and will benefit from better sunlight.
It'll take another 20 months to download all the data from the Ultima flyby.