Snowman or BB8? Ultima Thule Full of Surprises

New images of Kuiper Belt Object (KBO) Ultima Thule taken by NASA’s New Horizons spacecraft reveals a planetary body chock full of surprises.  The tiny 20-mile long object, 4 billion miles from Earth, has only been seen at close range since Monday. From the first 1 pixel image to the 2800 pixel image released today — and much better resolution photos on the way — scientists now know that Ultima Thule really is Ultima and Thule, two objects joined together since the earliest period of solar system formation.

The New Horizons mission team chose the nickname Ultima Thule after a public naming contest because of its meaning “a place beyond the known horizons.”  Indeed, no spacecraft has flown by an object so far from Earth before.  It was discovered using the Hubble Space Telescope in 2014, seven years after the spacecraft was launched.  Its official name is 2014 MU 69.

While there are many theories about how the solar system formed, the visit to this primitive world, virtually untouched for 4.5 billion years, is providing hard data on which those theories now can be tested.  One of those is whether two bodies might have joined together forming a “bilobate” and the answer to that is yes.  Ultima Thule has two lobes, different objects that formed independently.

New Horizons Principal Investigator (PI) Alan Stern of the Southwest Research Institute (SwRI) joked at a press conference today that the science team needed to give each lobe a name and, not being very creative, decided to call the larger one Ultima and the smaller one Thule.

Stern said Ultima is about three times the volume of Thule.

The first, blurry image of the object released just yesterday suggested it looked like a bowling pin or peanut, but Stern said now it reminds him of a snowman.

While some agreed, many in the Twitterverse saw BB8 from Star Wars instead.

Amazing to think how far away #UltimaThule. Superb work from @NASA however to me it looks like BB8. pic.twitter.com/UNiJ029yuP

— Richard Payne (@RockyTheTyke) January 2, 2019

Because of the 4 billion mile distance and low power of the spacecraft’s power source (15 watts), it will take 20 months for all the data and images to get back to Earth. What was presented at today’s briefing is very preliminary.

While the shape was not a surprise, the fact that it is two conjoined objects — a “contact binary” — seemed to stun the science team.  Jeff Moore, New Horizons Geology and Geophysics Lead from NASA’s Ames Research Center, postulated that the two objects formed at the same time and, by processes not yet understood, very slowly came together, basically resting on each other.  He described it as an “extremely” slow collision not unlike bumping into another car when parking so gently that there would be no need to exchange insurance information.

The object is rotating once every 15 hours give or take an hour according to SwRI’s Cathy Olkin, Deputy Project Scientist.  The science team thinks it would have to spin at a much greater rate for the two pieces to come apart.  As for its color, co-Investigator Carly Howett, also from SwRI, confirmed that “we can now definitively say that Ultima Thule is red,” although the neck is less so.

The images returned in time for today’s press conference were taken while the spacecraft was approaching Ultima Thule, with the Sun directly behind the spacecraft.  That meant no shadows, which would reveal more surface features, like craters. Those should show up in future images. Another press conference is scheduled for tomorrow.

Moore said Ultima Thule is an example of the very oldest objects in the solar system, one of “the first planetesimals.” Unlike those closer to the Sun that formed into planets and moons, it remains as it was at the beginning.  It is a “time machine, like a wayback machine set to time zero and that has brought us back to the very beginning of solar system history to a place where we can observe the most primordial building blocks of the planets.”

Stern was asked about the team’s decision to call the object Ultima Thule even though the term has an association with Nazis. He rejoined that it has been in use for centuries and “is a wonderful meme for exploration, and that’s why we chose it, and I would say just because some bad guys once liked that term, we’re not going to let them hijack it.”