Accurate geometric albedo, shape, and size of Hi'iaka from a stellar occultation

Estela Fernández-Valenzuela; Jose Luis Ortiz; Bryan J Holler; Bruno Sicardy; Flavia L Rommel; Mónica Vara-Lubiano; Nicolas Morales; Frederic Vachier; Josselin Desmars; Mike Kretlow; Roberto Vieira-Martins; Emmanuel Jehin; Marin Ferrais; Pablo Santos-Sanz; Zafar Rustamkulov; Alexander de la Vega; Elizabeth Warner; Zouhair Benkhaldoun; Roxanne Kamin; Al Ryan; Bernie Earls; Dennis Conti; Julien de Wit; Artem Burdanov; Richard Francini; Philip Langill; Ruben Morales; Wesley Fraser; Csaba Kiss; András Pál; Damya Souami; Jean Lecacheux; Felipe Braga-Ribas; René Duffard; Alvaro Alvarez-Candal; Gustavo Benedetti-Rossi; Bruno Morgado; Julio I B Camargo; Altair Ramos Gomes Júnior; Marcelo Assafin; Djounai Baba Aissa; Zaki Grigahcene; Marc W Buie; Javier Licandro; Miguel R Alarcon; Miquel Serra-Ricart; Alberto Castro-Tirado; Emilio Jesus Fernandez-Garcia; Ramón Iglesias-Marzoa; Francisco J Galindo-Guil; Hugo González; Rui Gonçalves; Adam Rengstorf; Randy Flynn; Aart Olsen; Bill Hanna; Jason Barnes; Joseph A A'Hearn; Steven M Kreyche; William J Miller; Lillian E Mortensen; Thomas C Gibson; Gary Walker; Gerogia Stolle-McAllister; Gregory A Feiden; Joseph Froetschel; Suzanne Steel; Destin Encardes; R Scott Fisher; Alton Luken; Eric Holcomb; Daniel Caton; Bob Dunford; Dmitry Monin

doi:10.1038/s41467-025-65749-1

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Accurate geometric albedo, shape, and size of Hi'iaka from a stellar occultation

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Accurate geometric albedo, shape, and size of Hi'iaka from a stellar occultation

Estela Fernández-Valenzuela, Jose Luis Ortiz, Bryan J Holler, Bruno Sicardy, Flavia L Rommel, Mónica Vara-Lubiano, Nicolas Morales, Frederic Vachier, Josselin Desmars, Mike Kretlow, …

Nature communications, Vol.16, 10926

12/01/2025

DOI: https://doi.org/10.1038/s41467-025-65749-1

PMID: 41326341

Abstract

Stellar occultations, when a distant object passes in front of a star and casts a shadow on Earth, are a powerful tool to probe the physical properties of solar system bodies. They enable precise size and shape measurements and can reveal rings, satellites, atmospheres, or surface features. Here we present results from two stellar occultations by Hi'iaka, dwarf planet Haumea's largest satellite, observed in April 2021. The second event yielded the first documented multi-chord occultation involving a trans-Neptunian satellite other than Charon. Combining these data with photometric observations, we find that Hi'iaka is a triaxial ellipsoid with a volume-equivalent diameter of 370 ± 20 km and a density of 640 ± 80 kg/m³, indicating a porous interior. The visible geometric albedo is , (∼ higher than Haumea's). The combination of low density and rapid rotation (9.68 ± 0.02 hours), under the assumption of a homogeneous body, indicates that Hi'iaka deviates from hydrostatic equilibrium.

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Title: Accurate geometric albedo, shape, and size of Hi'iaka from a stellar occultation
Creators: Estela Fernández-Valenzuela - University of Central Florida
Jose Luis Ortiz - Instituto de Astrofísica de Andalucía
Bryan J Holler - Space Telescope Science Institute
Bruno Sicardy - Laboratoire d’études spatiales et d’instrumentation en astrophysique
Flavia L Rommel - University of Central Florida
Mónica Vara-Lubiano - Instituto de Astrofísica de Andalucía
Nicolas Morales - Instituto de Astrofísica de Andalucía
Frederic Vachier - Institut de Mécanique Céleste et de Calcul des Éphémérides
Josselin Desmars - Institut de Mécanique Céleste et de Calcul des Éphémérides
Mike Kretlow - Instituto de Astrofísica de Andalucía
Roberto Vieira-Martins - National Observatory
Emmanuel Jehin - University of Liège
Marin Ferrais - University of Central Florida
Pablo Santos-Sanz - Instituto de Astrofísica de Andalucía
Zafar Rustamkulov - Johns Hopkins University
Alexander de la Vega - Johns Hopkins University
Elizabeth Warner - University of Maryland, College Park
Zouhair Benkhaldoun - Cadi Ayyad University
Roxanne Kamin - Ryan Observatory, Muddy Run, Bethesda Church Road West Holtwood, Holtwood, PA 17532, USA
Al Ryan - Ryan Observatory, Muddy Run, Bethesda Church Road West Holtwood, Holtwood, PA 17532, USA
Bernie Earls - Ryan Observatory, Muddy Run, Bethesda Church Road West Holtwood, Holtwood, PA 17532, USA
Dennis Conti - American Association of Variable Star Observers
Julien de Wit - Planetary Science Institute
Artem Burdanov - Planetary Science Institute
Richard Francini - American Association of Variable Star Observers
Philip Langill - University of Calgary
Ruben Morales - University of Calgary
Wesley Fraser - Herzberg Institute of Astrophysics
Csaba Kiss - Hungarian Academy of Sciences
András Pál - Hungarian Academy of Sciences
Damya Souami - Laboratoire d’études spatiales et d’instrumentation en astrophysique
Jean Lecacheux - Laboratoire d’études spatiales et d’instrumentation en astrophysique
Felipe Braga-Ribas - Laboratório Interinstitucional de e-Astronomia
René Duffard - Instituto de Astrofísica de Andalucía
Alvaro Alvarez-Candal - University of Alicante
Gustavo Benedetti-Rossi - Universidade Estadual Paulista (Unesp)
Bruno Morgado - Laboratório Interinstitucional de e-Astronomia
Julio I B Camargo - Laboratório Interinstitucional de e-Astronomia
Altair Ramos Gomes Júnior - Universidade Federal de Uberlândia
Marcelo Assafin - Laboratório Interinstitucional de e-Astronomia
Djounai Baba Aissa - Centre de Recherche en Astronomie Astrophysique et Géophysique
Zaki Grigahcene - Centre de Recherche en Astronomie Astrophysique et Géophysique
Marc W Buie - Southwest Research Institute
Javier Licandro - Instituto de Astrofísica de Canarias
Miguel R Alarcon - Instituto de Astrofísica de Canarias
Miquel Serra-Ricart - Instituto de Astrofísica de Canarias
Alberto Castro-Tirado - Instituto de Astrofísica de Andalucía
Emilio Jesus Fernandez-Garcia - Instituto de Astrofísica de Andalucía
Ramón Iglesias-Marzoa - Centro de Estudios de Física del Cosmos de Aragón
Francisco J Galindo-Guil - Centro de Estudios de Física del Cosmos de Aragón
Hugo González - Vigo
Rui Gonçalves - Plan Occult, Tomar, Portugal
Adam Rengstorf - Purdue University Northwest
Randy Flynn - Squirrel Valley Observatory, 3870 River Rd, Columbus, NC, 28722-6767, USA
Aart Olsen - International Occultation Timing Association (IOTA), 16348 E Glenbrook Blvd, Fountain Hills, AZ, 85268-2206, USA
Bill Hanna - International Occultation Timing Association (IOTA), 16348 E Glenbrook Blvd, Fountain Hills, AZ, 85268-2206, USA
Jason Barnes - University of Idaho
Joseph A A'Hearn - University of Idaho
Steven M Kreyche - University of Idaho
William J Miller - University of Idaho
Lillian E Mortensen - University of Idaho
Thomas C Gibson - University of Idaho
Gary Walker - Maria Mitchell Association
Gerogia Stolle-McAllister - Maria Mitchell Association
Gregory A Feiden - University of North Georgia
Joseph Froetschel - University of North Georgia
Suzanne Steel - University of North Georgia
Destin Encardes - University of North Georgia
R Scott Fisher - University of Oregon
Alton Luken - University of Oregon
Eric Holcomb - University of Oregon
Daniel Caton - Appalachian State University
Bob Dunford - International Occultation Timing Association (IOTA), 16348 E Glenbrook Blvd, Fountain Hills, AZ, 85268-2206, USA
Dmitry Monin - National Research Council, Herzberg Astrononomy and Astrophysics Research Centre, 5071 West Saanich Road, Victoria, BC, Canada
Publication Details: Nature communications, Vol.16, 10926
Publisher: Springer
Identifiers: 996865256901851
Academic Unit: Physics
Language: English
Resource Type: Journal article