Arrokoth

Arrokoth is a small trans-Neptunian object in the Kuiper belt, visited by NASA’s New Horizons spacecraft in 2019. Its two joined lobes preserve evidence of gentle formation in the early Solar System.

Contact binary: A body made of two formerly separate objects joined in physical contact. Arrokoth’s two lobes meet at a narrow neck, making it a clear contact-binary example.
New Horizons: A NASA spacecraft launched in 2006 to explore Pluto, the Kuiper belt, and the outer Solar System. Its 2019 flyby supplied nearly all detailed knowledge of Arrokoth.
Marc Buie: An American planetary astronomer whose work includes the discovery and study of distant Solar System objects. Buie led the team that discovered Arrokoth in 2014.
Kuiper belt exploration: Spacecraft and telescope investigations of the icy bodies beyond Neptune. Arrokoth became the most distant and primitive object explored at close range by a spacecraft.
Planetesimal: A solid body formed from dust and smaller particles during the assembly of a planetary system. Arrokoth is interpreted as a preserved planetesimal from the Solar System’s formation.
Ultima Thule: The informal name used for Arrokoth before its official naming in 2019. This name appeared in mission planning and early reports about the flyby target.
Hubble Space Telescope: A space observatory launched in 1990 that observes the universe across ultraviolet, visible, and near-infrared wavelengths. Hubble observations helped identify Arrokoth as a suitable New Horizons flyby target.
Planetary accretion: The growth of planets through the accumulation and collision of smaller solid bodies. Arrokoth’s joined lobes inform models of the earliest stages of this process.
Streaming instability: A process in a protoplanetary disk that concentrates dust grains into dense clumps capable of gravitational collapse. This mechanism may explain how Arrokoth’s precursor bodies formed in the early Solar System.
Kuiper belt: A region beyond Neptune containing icy bodies left over from the Solar System’s formation. Arrokoth is a member of this distant population.

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