Goibniu is 680 ± 34 km (423 ± 21 mi) in diameter, according to measurements of itsinfraredthermal emission by theHerschel andSpitzer space telescopes.[3] It shows small variations in brightness (0.16magnitudes) over its 5.86-hourrotation period.[7] Some astronomers have suggested that Goibniu is large enough that it could be adwarf planet.[11][12] However, the shape of Goibniu is unknown–it could either be a spheroid with small albedo spots or an ellipsoid whose rotation axis is pointed towards Earth.[7] Furthermore, its low albedo suggests it has never been resurfaced and thus is unlikely to have the planetary geology thought to be typical of dwarf planets.[13]
Precovery observations of Goibniu were first reported by astronomerReiner Stoss and published by the MPC on 10 June 2004.[16] These precovery observations, which came fromDigitized Sky Survey images from 1993–1997, allowed for an accuratedetermination of Goibniu's orbit without the need for follow-up observations.[16] Even earlier precovery observations have since been reported, from dates as early as December 1954.[1]
This object has theminor planetprovisional designation2004 GV9, which was given by the MPC in the discovery announcement.[14] The provisional designation indicates the year and half-month of the object's discovery date.[17]2004 GV9 received its permanentminor planet catalog number of 90568 from the MPC on 30 August 2004.[18]
Until 2025,2004 GV9 did not have a proper name and the discoverers' privilege for naming this object expired ten years after it was numbered.[1][19]: 6 According to naming guidelines by theInternational Astronomical Union'sWorking Group for Small Bodies Nomenclature,2004 GV9 was open for name suggestions that relate to creation myths, as recommended for Kuiper belt objects in general.[19]: 8 On 1 September 2025, it was officially namedGoibniu, after the Irish god of metallurgy and hospitality.[20]
Goibniu is located in the classical region of theKuiper belt 39–48 AU from the Sun,[4]: 53 and is thus classified as aclassical Kuiper belt object (sometimes known as a "cubewano").[4]: 55 The high orbital inclination of Goibniu makes it a dynamically "hot" member of the classical Kuiper belt.[3]: 3 The hot classical Kuiper belt objects are believed to have beenscattered by Neptune's gravitational influence during the Solar System's early history.[22]: 230
^These orbital elements are expressed in terms of theSolar System Barycenter (SSB) as the frame of reference.[6] Due to planetaryperturbations, the Sun revolves around the SSB at non-negligible distances, so heliocentric-frame orbital elements and distances can vary in short timescales as shown inJPL-Horizons.[21]
^abcdeYeung, W. K. Y.; Stevens, B. L.; Sanchez, S.; Stoss, R.; Nomen, J.; Pravdo, S.; et al. (14 April 2004)."MPEC 2004-G32 : 2004 GV9".Minor Planet Electronic Circular. 2004-G32. Minor Planet Center.Bibcode:2004MPEC....G...32Y. Retrieved6 January 2010.
^abStoss, R.; McNaught, R. H.; Sanchez, S.; Nomen, J.; Holvorcem, P. R.; Schwartz, M.; et al. (10 June 2004)."MPEC 2004-L17 : 2004 GV9".Minor Planet Electronic Circular. 2004-L17. Minor Planet Center.Bibcode:2004MPEC....L...17S. Retrieved24 August 2025.
^Pinilla-Alonso, Noemí; Stansberry, John; Holler, Bryan (2020). "Chapter 18 - Surface properties of large TNOs: Expanding the study to longer wavelengths with the James Webb Space Telescope". In Prialnik, Dina; Barucci, Maria Antonietta; Young, Leslie (eds.).The Transneptunian Solar System. Elsevier. pp. 395–412.arXiv:1905.12320.Bibcode:2019arXiv190512320P.doi:10.1016/B978-0-12-816490-7.00018-7.ISBN978-0-12-816490-7.
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