New Years with Ultima Thule – that’s far out.

Nature reports on the New Horizon space probe’s date for New Years – with Ultima Thule (formally, 2014 MU69), the most distant object visited by one of our spacecraft:

MU69 will be the most primordial object ever visited, and its appearance could tell scientists more about the disk of gas and dust from which the Solar System coalesced more than 4.5 billion years ago. “We’re going to an entirely new type of world,” says Alan Stern, the mission’s principal investigator and a planetary scientist at the Southwest Research Institute in Boulder, Colorado.

Like Pluto, MU69 is a resident of the Kuiper belt, a collection of dwarf planets and smaller rocks that orbit the Sun beyond Neptune. But that’s where the similarities end. Pluto is more than 2,370 kilometres across — big enough to have an internal geological engine that drives activities such as mountain-building. MU69 is a pipsqueak, probably only around 30 kilometres across, and thus might be geologically stagnant.

The space rock is so faint and distant that ground-based telescopes see it as only a pixel or two. Even the Hubble Space Telescope had a hard time discovering it in 2014. New Horizons scientists have had to go to great lengths to work out anything they can about the object before their spacecraft arrives.

It appears to be elongated, with two lobes like a peanut — but it could also be two objects orbiting one another closely.

The spacecraft’s closest approach to MU69 will come at 12:33 a.m. US East coast time on 1 January. The spacecraft won’t be in communication with mission control at the time, because it will be busy snapping MU69 as it whizzes past. Then it will take more than six hours to radio that information, at light speed, back to Earth.