Jan. 2, 2019: The first high-resolution images of Ultima Thule have reached Earth following New Horizons’ historic flyby on New Year’s Day. Hot off the presses, the photos reveal a pair of roughly spherical planetestimals stuck together in the middle. The contact binary strangely resembles BB-8:
“This flyby is a historic achievement,” says New Horizons Principal Investigator Alan Stern of the Southwest Research Institute in Boulder, Colorado. “Never before has any spacecraft team tracked down such a small body so far away in the abyss of space. We’re getting our first close-up look at ancient planetesimals.”
Planetestimals are the building blocks of planets. Here in the inner solar system, no pristine examples remain for us to study. They have been swallowed by planets, hammered by asteroids, and scorched by solar radiation. Ultima Thule, however, has been preserved in the deep freeze of the outer solar system for more than 4 billion years. It is truly a relic of the genesis of planets.
Mission scientists believe that Ultima Thule formed by accretion. A swarm of smaller planetesimals gathered under the pull of their own meagre gravity to form two spherical bodies, medium-sized planetesimals which themselves slowly bumped together and stuck. The result was Ultima Thule.
This is just the beginning of Ultima Thule’s revelations. First images released today have a resolution of about 140 meters per pixel. Images arriving in the days and weeks ahead will be as much as 5 times sharper, possibly revealing craters, hills, landslides, rilles and other unknowns.
New Horizons also scanned the area for tiny moons–the debris of the original swarm that gave birth to this strange object. Detections, if any, will be revealed in future transmissions from the spacecraft.