The New Horizons probe made its flyby of Pluto in July of 2015 and then sped on into the Kuiper Belt, a vast region of space inhabited by debris from the earliest era in the formation of the solar system. As a mission bonus, the trajectory of the spacecraft was subsequently nudged by its engine to send the craft past the recently discovered Kuiper object labeled 2014 MU69. With the help of a public contest, the object was given the more interesting name of Ultima Thule –

Thule was a mythical, far-northern island in medieval literature and cartography. Ultima Thule means “beyond Thule”– beyond the borders of the known world—symbolizing the exploration of the distant Kuiper Belt and Kuiper Belt objects that New Horizons is performing, something never before done.

On New Years Day 2019 at 12:33 am EST, New Horizons will make its closest approach to Ultima Thule, which is about 30 kilometers (20 miles) in size. In fact, it will fly three times closer than its nearest distance from the surface of Pluto. Ultima Thule will be the farthest object ever targeted by a spacecraft from earth.

The Kuiper Belt lies in the so-called “third zone” of our solar system, beyond the terrestrial planets (inner zone) and gas giants (middle zone). This vast region contains billions of objects, including comets, dwarf planets like Pluto and “planetesimals” like Ultima Thule. The objects in this region are believed to be frozen in time — relics left over from the formation of the solar system. Credits: NASA/JHUAPL/SwRI

Here is an update: All About Ultima: New Horizons Flyby Target is Unlike Anything Explored in Space – New Horizons – Dec.26.2018

Marc Buie, New Horizons co-investigator from the Southwest Research Institute in Boulder, Colorado, and members of the New Horizons science team discovered Ultima using the Hubble Space Telescope in 2014. The object is so far and faint in all telescopes, little is known about the world beyond its location and orbit. In 2016, researchers determined it had a red color. In 2017, a NASA campaign using ground-based telescopes traced out its size — just about 20 miles (30 kilometers) across — and irregular shape when it passed in front of a star, an event called a “stellar occultation.”

From its brightness and size, New Horizons team members have calculated Ultima’s reflectivity, which is only about 10 percent, or about as dark as garden dirt. Beyond that, nothing else is known about it — basic facts like its rotational period and whether or not it has moons are unknown.

“All that is about to dramatically change on New Year’s Eve and New Year’s Day,” said New Horizons Principal Investigator Alan Stern, also of SwRI. “New Horizons will map Ultima, map its surface composition, determine how many moons it has and find out if it has rings or even an atmosphere. It will make other studies, too, such as measuring Ultima’s temperature and perhaps even its mass. In the space of one 72-hour period, Ultima will be transformed from a pinpoint of light — a dot in the distance — to a fully explored world. It should be breathtaking!”

A sequence of images from the New Horizons camera shows the object growing larger in the field of view:

Here is a preview discussion of the flyby:

Members of the New Horizons team previewed the mission’s New Year’s 2019 flyby of the Kuiper Belt object nicknamed Ultima Thule during a media briefing at the American Astronomical Society’s Division for Planetary Sciences Meeting in Knoxville, Tennessee. The Ultima flyby, with closest approach set for 12:33 a.m. EST in Jan. 1, will be the most distant planetary encounter in history. Team members covered the significance and challenges of this flyby, its science goals and operational timelines, and the Kuiper Belt in the context of solar system exploration.

Presenters are: Alan Stern, principal investigator, Southwest Research Institute Carey Lisse, science team collaborator, Johns Hopkins Applied Physics Laboratory Hal Weaver, project scientist, Johns Hopkins Applied Physics Laboratory Kelsi Singer, co-investigator, Southwest Research Institute

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