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.

[33] The name Arrokoth was chosen by the New Horizons team to represent the Powhatan people indigenous to the Tidewater region of Virginia and Maryland in the eastern United States.

[34] The Hubble Space Telescope and the Johns Hopkins University Applied Physics Laboratory, which were prominently involved in Arrokoth's discovery, were both operated from the Tidewater region of Maryland.

[34][35] With the permission of the elders of the Pamunkey Indian Tribe of the Powhatan nation, the name Arrokoth was proposed to the IAU and formally announced by the New Horizons team in a ceremony held at the NASA Headquarters in the District of Columbia on 12 November 2019.

[c] Arrokoth is a contact binary consisting of two lobes (lobi) attached by a narrow neck or waist, which is encircled by a bright band named Akasa Linea.

[39] Spectral measurements from LEISA revealed the presence of methanol and complex organic compounds on the surface of Arrokoth, but no evidence of water ice.

[50] Given the abundance of methanol on Arrokoth's surface, it is predicted that formaldehyde-based compounds resulting from irradiation should also be present, albeit in the form of complex macromolecules.

[51] Arrokoth's spectrum shares similarities with that of 2002 VE95 and the centaur 5145 Pholus, which also display strong red spectral slopes along with signs of methanol present on their surfaces.

[39] Preliminary observations by the Hubble Space Telescope in 2016 revealed that Arrokoth has a red coloration, similar to other Kuiper belt objects and centaurs like Pholus.

[55][50] However, less volatile materials such as methanol, acetylene, ethane, and hydrogen cyanide could be retained over a longer period of time, and may likely account for the reddening and production of tholins on Arrokoth.

[10] Arrokoth's surface has few small craters (from 1 km (0.62 mi) in size to the limits of photographic resolution), implying a paucity of impacts throughout its history.

[60] Another bright region (rm), located at the equatorial end of Weeyo, exhibits rough terrain along with several topographic features that have been identified as possible pits, craters, or mounds.

[39] Weeyo does not display distinct units of rolling topography near Sky, likely as a result of resurfacing caused by the impact event that created the crater.

[65] Ammonia vapor present on the surface of Arrokoth would solidify around Akasa Linea, where gases cannot escape due to the concave shape of the neck.

[79][80] Arrokoth's orbit is inclined to the ecliptic plane by 2.45 degrees, relatively low compared to other classical Kuiper belt objects such as Makemake.

[81] Since Arrokoth has a low orbital inclination and eccentricity, it is part of the dynamically cold population of classical Kuiper belt objects, which are unlikely to have undergone significant perturbations by Neptune during its outward migration in the past.

The cold classical population of Kuiper belt objects are thought to be remnant planetesimals left over from the accretion of material during the formation of the Solar System.

[8] Due to the high axial tilt of its rotation, the solar irradiance of the northern and southern hemispheres of Arrokoth varies greatly over the course of its orbit around the Sun.

[38][53] Arrokoth had likely formed in a colder environment within a dense, opaque region of the early Kuiper belt where the Sun appeared heavily obscured by dust.

[90][45] The New Horizons team hypothesizes that the two progenitor objects formed with initially rapid rotations, causing their shapes to become flattened due to centrifugal forces.

[38][90] In an alternative hypothesis formulated by researchers of the Chinese Academy of Sciences and the Max Planck Institute in 2020, the flattening of Arrokoth may have resulted from the process of sublimation-driven mass loss over a timescale of several million years after the merging of the lobi.

After the surrounding dust and nebula subsided, solar radiation was no longer obstructed, allowing for photon-induced sublimation to occur in the Kuiper belt.

[39][89] The progenitor objects must have also merged obliquely at angles greater than 75 degrees in order to account for the present shape of Arrokoth's thin neck while keeping the lobi intact.

[57][18] Arrokoth was discovered on 26 June 2014 using the Hubble Space Telescope during a preliminary survey to find a suitable Kuiper belt object for the New Horizons spacecraft to fly by.

[92][93] In order to find these fainter Kuiper belt objects, the New Horizons team initiated a search for suitable targets with the Hubble Space Telescope on 16 June 2014.

[102] When they found that none of their telescopes had observed the object's shadow, it was initially speculated that Arrokoth might be neither as large nor as dark as previously expected, and that it might be highly reflective or even a swarm.

[103] On 10 July 2017, the airborne telescope SOFIA was successfully placed close to the predicted centerline for the second occultation while flying over the Pacific Ocean from Christchurch, New Zealand.

[10] Closest approach occurred on 1 January 2019, at 05:33 UTC (Spacecraft Event Time – SCET)[111][124] at which point it was 43.4 AU from the Sun in the direction of the constellation Sagittarius.

[111] The science objectives of the flyby include characterizing the geology and morphology of Arrokoth, and mapping the surface composition (searching for ammonia, carbon monoxide, methane, and water ice).

[111][128] From Hubble observations, faint, small satellites orbiting Arrokoth at distances greater than 2,000 km (1,200 mi) have been excluded to a depth of >29th magnitude.