Trans-Neptunian object
Trans-Neptunian object or TNO is a name astronomers give to any minor planet in the Solar System which orbits (travels around) the Sun beyond the planet Neptune. There are over a thousand Trans-Neptunian objects.[1] Many are in the Kuiper belt.
Trans-Neptunian Object Media
Pluto, the first known TNO, imaged by New Horizons in 2015.
Distribution of trans-Neptunian objects, with semi-major axis on the horizontal, and perihelion on the vertical axis. Scattered disc objects occupy the wide horizontal region in grey and purple, while objects that are in resonance with Neptune are in red. Extreme trans-Neptunian objects and sednoids are in pink, brown, and yellow. Finally, the classical Kuiper belt is in blue.
Looking back at Pluto, the largest visited KBO so far
Comparison of sizes, albedo, and colors of various large trans-Neptunian objects with sizes of >700 km. The dark colored arcs represent uncertainties of the object's size.
Size comparison between the Moon, Neptune's moon Triton, Pluto, several large TNOs, and the dwarf planet Ceres. Their respective shapes are not represented.
Kuiper belt object 486958 Arrokoth, in images taken by the New Horizons spacecraft
Overview of trans-Neptunian objects with extreme TNOs grouped into three categories at the top.
Sedna's orbit takes it far beyond even the Kuiper belt (30–50 AU), out to nearly 1,000 AU (Sun–Earth distance)
