Ultima Thule

Ultima Thule is a trans-Neptunian object located in the Kuiper belt. It is a contact binary, with estimated dimensions of 31 by 19 km (20 by 10 mi), consisting of a larger body (“Ultima”) three times the volume of the smaller (“Thule”). With an orbital period of 298 years and a low inclination and eccentricity, it is classified as a classical Kuiper belt object. Due to its distant location, it is suspected to have not undergone significant gravitational perturbations and to be only moderately cratered. With the New Horizons space probe’s flyby on 1 January 2019, 2014 MU69 became the farthest object in the Solar System visited by a spacecraft, and is believed to be the most primitive, both bodies being planetesimal aggregates of much smaller building blocks. It was discovered on June 26, 2014 by astronomers using the Hubble Space Telescope as part of a search for a Kuiper belt object for the New Horizons mission to target in its first extended mission; it was chosen over two other candidates to become the primary target of the mission. Its nickname, a Greco-Latin term for a “place beyond the known world”, was chosen as part of a public competition in 2018.