Extreme trans-Neptunian object in the context of "List of trans-Neptunian objects"

541132 Leleākūhonua (/ˌlɛleɪɑːˌkuːhoʊˈnuːə/; provisional designation 2015 TG₃₈₇) is an extreme trans-Neptunian object and sednoid in the outermost part of the Solar System. It was first observed on 13 October 2015, by astronomers at the Mauna Kea Observatories, Hawaii. Based on its discovery date near Halloween and the letters in its provisional designation 2015 TG₃₈₇, the object was informally nicknamed "The Goblin" by its discoverers and later named Leleākūhonua, comparing its orbit to the flight of the Pacific golden plover. It was the third sednoid discovered, after Sedna and 2012 VP113, and measures around 220 kilometers (140 miles) in diameter.

2013 SY₉₉, also known by its OSSOS survey designation uo3L91, is a trans-Neptunian object discovered on September 29, 2013 by the Outer Solar System Origins Survey using the Canada–France–Hawaii Telescope at Mauna Kea Observatory. This object orbits the Sun between 50 and 1,300 AU (7.5 and 190 billion km), and has a barycentric orbital period of nearly 20,000 years. It has the fourth largest semi-major axis for an orbit with perihelion beyond 38 AU. 2013 SY₉₉ has one of highest perihelia of any known extreme trans-Neptunian object, behind sednoids including Sedna (76 AU), 2012 VP113 (80 AU), and Leleākūhonua (65 AU).

2021 RR₂₀₅ is an extreme trans-Neptunian object discovered by astronomers Scott Sheppard, David Tholen, and Chad Trujillo with the Subaru Telescope at Mauna Kea Observatory on 5 September 2021. It resides beyond the outer extent of the Kuiper belt on a distant and highly eccentric orbit detached from Neptune's gravitational influence, with a large perihelion distance of 55.5 astronomical units (AU). Its large orbital semi-major axis (~1,000 AU) suggests it is potentially from the inner Oort cloud. 2021 RR₂₀₅ and 2013 SY99 both lie in the 50–75 AU perihelion gap that separates the detached objects from the more distant sednoids; dynamical studies indicate that such objects in the inner edge of this gap weakly experience "diffusion", or inward orbital migration due to minuscule perturbations by Neptune. While Sheppard considers 2021 RR₂₀₅ a sednoid, researchers Yukun Huang and Brett Gladman do not.

2021 RR₂₀₅'s heliocentric distance was 60 AU when it was discovered. It has been detected in precovery observations by the Dark Energy Survey at Cerro Tololo Observatory from as early as July 2017. It last passed perihelion in the early 1990s and is now moving outbound from the Sun.

This is a list of unnumbered trans-Neptunian objects (TNOs) first observed since 1993 and grouped by the year of principal provisional designation. The data is sourced from the Minor Planet Center's (MPC) List of Trans Neptunian Objects, List Of Centaurs and Scattered-Disk Objects, List Of Other Unusual Objects, and Database Search. These objects will eventually be numbered as secured discoveries with an official discoverer determined by the MPC. Until then, additional observations are needed to sufficiently decrease an object's orbital uncertainty. As of November 2025, there are 4,518 unnumbered objects, defined here as minor planets with a semi-major axis larger than 30.1 AU (Neptune's average orbital distance from the Sun).

The list also contains information from "Johnston's Archive", such as an object's diameter, its dynamical class and binary status with the satellite's diameter, as well as its albedo, spectral taxonomy and B–R color index. Members of the extreme trans-Neptunian objects (ESDOs, EDDOs and sednoids) – with a semi-major axis greater than 150 AU and perihelion greater than 30 AU – are also identified.