(678191) 2017 OF69

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678191 (2017 OF69) is a large plutino, a type of distant object in the Kuiper belt that sits in a 2:3 resonance with Neptune (it orbits the Sun twice for every three Neptune orbits).

Discovery and designation
- First seen on 26 July 2017 by David Tholen, Scott Sheppard, and Chad Trujillo at Mauna Kea Observatories in Hawaii.
- Not announced publicly until 31 May 2018 after further observations refined its orbit.
- Numbered 678191 on 22 March 2024; as of January 2026 it has not been named.

Orbit and size
- Orbits the Sun about 31.4 to 47.8 astronomical units away, completing one orbit every about 249.5 years (91,128 days).
- Orbital eccentricity ~0.21 and inclination ~13.7 degrees.
- Semi-major axis about 39.6 AU.
- Estimated diameter about 533 km, assuming a reflectivity (albedo) of 0.09.
- No known moons; no high-resolution images have been taken yet. A planned Hubble Space Telescope observation in 2026 aims to check for moons.

Context
- 2017 OF69 is among the largest plutinos known, ranking fifth after Pluto, Orcus, Achlys, and Ixion.
- Its rotation period, pole orientation, and exact shape remain unknown.