541132 Leleākūhonua
Third sednoid discovered, with an orbit suggesting Planet Nine.
541132 Leleākūhonua, originally labeled 2015 TG387, is a distant object in the outer Solar System classified as an extreme trans-Neptunian object and a sednoid. It was first spotted on 13 October 2015 using telescopes at Hawaii’s Mauna Kea Observatories. It is the third sednoid ever found, following Sedna and 2012 VP113, and has a diameter of roughly 220 kilometers (140 miles).
The object was discovered by American astronomers David Tholen, Chad Trujillo, and Scott Sheppard as part of a survey targeting regions beyond the Kuiper Cliff. The survey uses the 8.2-meter Subaru Telescope with its Hyper Suprime Camera at Mauna Kea for northern observations and the 4-meter Blanco Telescope with its Dark Energy Camera at Cerro Tololo in Chile for the south. Follow-up observations rely on the Magellan and Lowell Discovery telescopes. The same team also found 2012 VP113, 2014 SR349, and 2013 FT28.
Leleākūhonua takes roughly 55,000 years to orbit the Sun, traveling between about 65 and 2,800 AU away, with an average distance (semi-major axis) near 1,450 AU. Its orbit is highly elongated, with an eccentricity of 0.955, and is tilted 12° relative to the ecliptic. It belongs to the extreme trans-Neptunian objects and is the third sednoid known.
The object’s orbit, along with those of other distant trans-Neptunian bodies, hints at—but does not confirm—the existence of a hypothetical Planet Nine. As of 2019, Leleākūhonua was inbound at 78 AU from the Sun, roughly two and a half times farther than Pluto’s current distance. It will reach perihelion, its closest approach to the Sun, in 2078. Like Sedna, it was only detectable because it was on the inward leg of its orbit, suggesting many similar objects exist but are too far to be seen with current technology. Based on its discovery, Sheppard and colleagues estimate there may be about 2 million inner Oort cloud objects larger than 40 km (25 mi), with a combined mass of 1×10²² kg—roughly the mass of Pluto, a fraction of Earth’s moon, but several times the mass of the asteroid belt.
The Minor Planet Center numbered the object on 10 October 2019.
Quick Facts
- Minorplanet
- yes
- Background
- #C2E0FF
- Discoverer
- D. J. Tholen / C. Trujillo / S. S. Sheppard
- Discovery Site
- Mauna Kea Obs.
- Discovered
- 13 October 2015
- Mpc Name
- (541132) Leleākūhonua
- Pronounced
- lang · , · l · E · l · ei · aː · , · k · uː · h · ou · ˈ · n · uː · ə / haw · lelejaːkuːhoˈnuwə · lang
- Mp Category
- TNOsednoid
- Epoch
- 25 February 2023 (JD 2460000.5)
- Uncertainty
- 3
- Observation Arc
- 4763 d
- Earliest Precovery Date
- 5 October 2005
Facts from the source article.
Lore & Background
Leleākūhonua was first observed on 13 October 2015 at the Mauna Kea Observatory by American astronomers David Tholen, Chad Trujillo, and Scott Sheppard during a survey for objects beyond the Kuiper Cliff. The unofficial discovery was publicly announced on 1 October 2018. 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. It was later named Leleākūhonua, meaning 'it flies until land appears' in Hawaiian, suggested by students in the Hawaiian-language program A Hua He Inoa. The name compares its orbit to the flight of the Pacific golden plover.
The object orbits the Sun at a distance varying from 65 to about 2800 AU once roughly every 55,000 years, with a very high eccentricity of 0.955 and an inclination of 12°. It belongs to the extreme trans-Neptunian objects and is the third sednoid ever discovered. As of 2019, the object is inbound 78 AU from the Sun, about two-and-a-half times farther out than Pluto's current location, and will come to perihelion in 2078. Its size depends on assumed albedo; observations of a single-chord stellar occultation on 20 October 2018 suggested a diameter of 220 km, corresponding to an albedo of 0.21.
Reader's Guide
The orbit of Leleākūhonua, along with similar orbits of other distant trans-Neptunian objects, suggests but does not prove the existence of Planet Nine in the outer Solar System. As with Sedna, it would not have been found had it not been on the inner leg of its long orbit, implying that there may be many similar objects too distant to be detected by contemporary methods. Following its discovery, Sheppard et al. concluded that it implies a population of about 2 million inner Oort cloud objects larger than 40 km, with a combined total mass of 1×10^22 kg, about the mass of Pluto. This object was numbered by the Minor Planet Center on 10 October 2019 and formally named on 3 June 2020. Its name, suggested by Hawaiian-language students, evokes the migration of the kolea (Pacific golden plover) and compares the orbit to the flight of migratory birds, with a yearning to be near Earth.
Did You Know?
- It was the third sednoid ever discovered, after Sedna and 2012 VP113.
- The object will come to perihelion (closest approach to the Sun) in 2078.
- Its name was suggested by students in the Hawaiian-language program A Hua He Inoa and means 'it flies until land appears'.
More in Trans-Neptunian Objects 1-24
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