Arrokoth

486958 Arrokoth is a trans-Neptunian object located in the Kuiper belt. Arrokoth became the farthest and most primitive object in the Solar System visited by a spacecraft when the NASA space probe New Horizons conducted a flyby on 1 January 2019. Arrokoth is a contact binary 36 km (22 mi) long, composed of two planetesimals 21 and 15 km (13 and 9 mi) across, that are joined along their major axes. With an orbital period of about 298 years and a low orbital inclination and eccentricity, Arrokoth is classified as a cold classical Kuiper belt object.

Arrokoth was discovered on 26 June 2014 by astronomer Marc Buie and the New Horizons Search Team using the Hubble Space Telescope as part of a search for a Kuiper belt object for the New Horizons spacecraft to target in its first extended mission; it was chosen over two other candidates, 2014 OS393 and 2014 PN70, to become the primary target of the mission.

When Arrokoth was first observed by the Hubble Space Telescope in 2014, it was designated 1110113Y in the context of the telescope's search for Kuiper belt objects, and was nicknamed "11" for short. Its existence as a potential target of the New Horizons probe was announced by NASA in October 2014 and it was unofficially designated as "Potential Target 1", or PT1. Its official provisional designation, 2014 MU69, was assigned by the Minor Planet Center in March 2015, after sufficient orbital information had been gathered. The provisional designation indicates that Arrokoth was the 1745th minor planet to be assigned a provisional designation during the second half of June 2014. After further observations refining its orbit, it was given the permanent minor planet number 486958 on 12 March 2017.