[en] 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 Hiʻiaka, 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 0.76±0.15, (∼30% 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 Hiʻiaka deviates from hydrostatic equilibrium.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Fernández-Valenzuela, Estela; Florida Space Institute (University of Central Florida), 12354 Research Parkway, Partnership 1, 32826, Orlando, FL, USA
Ortiz, Jose Luis; Institute of Astrophysics of Andalusia
Holler, Bryan J.; Space Telescope Science Institute, Steven Muller Building, 3700 San Martin Drive Baltimore, MD, 21218, Baltimore, MD, USA ,
Sicardy, Bruno; Observatoire de Paris, Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique
Rommel, Flavia L.; Florida Space Institute (University of Central Florida), 12354 Research Parkway, Partnership 1, 32826, Orlando, FL, USA , Observatório Nacional, Ministério de Ciência, Tecnologia e Inovação, R. General José Cristino, 77, CEP 20921-400, Rio de Janeiro, RJ, Brazil , Laboratório Interinstitucional de e-Astronomia - LIneA, Av. Pastor Martin Luther King Jr 126, CEP 20765-000, Rio de Janeiro, RJ, Brazil
Vara-Lubiano, Mónica; Institute of Astrophysics of Andalusia
Morales, Nicolas; Institute of Astrophysics of Andalusia
Vachier, Frederic; Institut de mécanique céleste et de calcul des éphémérides, University of Paris, 77, Avenue Denfert-Rochereau, 75014, Paris, France ,
Desmars, Josselin; Institut de mécanique céleste et de calcul des éphémérides, University of Paris, 77, Avenue Denfert-Rochereau, 75014, Paris, France , Institut Polytechnique des Sciences Avancées IPSA, 63 boulevard de Brandebourg, 94200, Ivry-sur-Seine, France ,
Kretlow, Mike; Institute of Astrophysics of Andalusia
Vieira-Martins, Roberto; Observatório Nacional, Ministério de Ciência, Tecnologia e Inovação, R. General José Cristino, 77, CEP 20921-400, Rio de Janeiro, RJ, Brazil , Laboratório Interinstitucional de e-Astronomia - LIneA, Av. Pastor Martin Luther King Jr 126, CEP 20765-000, Rio de Janeiro, RJ, Brazil
Jehin, Emmanuel ; Université de Liège - ULiège > Unités de recherche interfacultaires > Space sciences, Technologies and Astrophysics Research (STAR)
Ferrais, Marin ; Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO) > COMets METeors and Asteroids (COMETA) ; Florida Space Institute (University of Central Florida), 12354 Research Parkway, Partnership 1, 32826, Orlando, FL, USA
Santos-Sanz, Pablo; Institute of Astrophysics of Andalusia
Rustamkulov, Zafar; Department of Earth and Planetary Science, Johns Hopkins University, 301 Olin Hall, 3400 N. Charles Street, 21218, Baltimore, MD, USA
de la Vega, Alexander; Johns Hopkins University, Department of Physics and Astronomy
Warner, Elizabeth; University of Maryland, Department of Astronomy
Kamin, Roxanne; Ryan Observatory, Muddy Run, Bethesda Church Road West Holtwood, PA 17532, Holtwood, USA
Ryan, Al; Ryan Observatory, Muddy Run, Bethesda Church Road West Holtwood, PA 17532, Holtwood, USA
Earls, Bernie; Ryan Observatory, Muddy Run, Bethesda Church Road West Holtwood, PA 17532, Holtwood, USA
Conti, Dennis; American Association of Variable Star Observers, Annapolis, MD, USA ,
de Wit, Julien; Department of Earth, Atmospheric and Planetary Scienec (EAPS), Massachusetts Av Bldg 54, Cambridge, MA, USA,
Burdanov, Artem; Department of Earth, Atmospheric and Planetary Scienec (EAPS), Massachusetts Av Bldg 54, Cambridge, MA, USA,
Francini, Richard; American Association of Variable Star Observers, Annapolis, MD, USA , Astronomical League and American Association of Variable Star Observers, 9201 Ward Parkway Suite 100, 64114, Kansas City, MO, USA
Langill, Philip; Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada
Morales, Ruben; Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada
Fraser, Wesley; National Research Council, Herzberg Astrononomy and Astrophysics Research Centre, 5071 West Saanich Road, Victoria, BC, Canada, Department of Physics and Astronomy, University of Victoria, Elliott Building, 3800 Finnerty Road, V8P 5C2, Victoria, BC, Canada ,
Kiss, Csaba; Konkoly Observatory, HUN-REN, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Konkoly Thege 15-17, H-1121, Budapest, Hungary
Pál, András; Konkoly Observatory, HUN-REN, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Konkoly Thege 15-17, H-1121, Budapest, Hungary , CSFK, MTA Centre of Excellence, Konkoly Thege 15-17, H-1121, Budapest, Hungary , ELTE Eötvös Loránd University, Institute of Physics and Astronomy, Pázmány Péter sétány 1/A, H-1171, Budapest, Hungary
Souami, Damya; Observatoire de Paris, Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique, -, Universite de Namur, Belgium, -
Lecacheux, Jean; Observatoire de Paris, Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique
Braga-Ribas, Felipe; Laboratório Interinstitucional de e-Astronomia - LIneA, Av. Pastor Martin Luther King Jr 126, CEP 20765-000, Rio de Janeiro, RJ, Brazil , Federal University of Technology - Paraná, PPGFA/UTFPR-Curitiba, Av. Sete de Stembro 3165, 80230-901, Curitiba, PR, Brazil ,
Duffard, René; Institute of Astrophysics of Andalusia
Alvarez-Candal, Alvaro; Institute of Astrophysics of Andalusia, University of Alacant, Spain
Benedetti-Rossi, Gustavo; Observatoire de Paris, Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique, -, -
Morgado, Bruno; Laboratório Interinstitucional de e-Astronomia - LIneA, Av. Pastor Martin Luther King Jr 126, CEP 20765-000, Rio de Janeiro, RJ, Brazil , Observatório do Valongo, Universidade Federal do Rio de Janeiro, Ladeira Pedro Antônio 43, CEP 20.080-090, Rio de Janeiro, RJ, Brazil ,
Camargo, Julio I. B.; Observatório Nacional, Ministério de Ciência, Tecnologia e Inovação, R. General José Cristino, 77, CEP 20921-400, Rio de Janeiro, RJ, Brazil , Laboratório Interinstitucional de e-Astronomia - LIneA, Av. Pastor Martin Luther King Jr 126, CEP 20765-000, Rio de Janeiro, RJ, Brazil ,
Júnior, Altair Ramos Gomes; Laboratório Interinstitucional de e-Astronomia - LIneA, Av. Pastor Martin Luther King Jr 126, CEP 20765-000, Rio de Janeiro, RJ, Brazil , Universidade Federal de Uberlândia (UFU), Instituto de Física, Av. Joñao Naves de Ávila 2121, Barrio Santa Mônica, Uberlândia, Brazil ,
Assafin, Marcelo; Laboratório Interinstitucional de e-Astronomia - LIneA, Av. Pastor Martin Luther King Jr 126, CEP 20765-000, Rio de Janeiro, RJ, Brazil , Observatório do Valongo, Universidade Federal do Rio de Janeiro, Ladeira Pedro Antônio 43, CEP 20.080-090, Rio de Janeiro, RJ, Brazil ,
Aissa, Djounai Baba; Center of Research in Astronomy, Astrophysics and Geophysics, CRAAG, bp − 63 Rte de l'Observatoire, Bouzareah Bouzareah, Algeria,
Grigahcene, Zaki; Center of Research in Astronomy, Astrophysics and Geophysics, CRAAG, bp − 63 Rte de l'Observatoire, Bouzareah Bouzareah, Algeria
Buie, Marc W.; Southwest Research Institute, 1050 Walnut St 300, 80302, Boulder, CO, USA
Licandro, Javier; Astrophysical Institute of the Canaries
Alarcon, Miguel R.; Astrophysical Institute of the Canaries
Serra-Ricart, Miquel; Astrophysical Institute of the Canaries
Castro-Tirado, Alberto; Institute of Astrophysics of Andalusia
Fernandez-Garcia, Emilio Jesus; Institute of Astrophysics of Andalusia
Iglesias-Marzoa, Ramón; Observatorio Astrofísico de Javalambre (OAJ), Centro de estudios de física del cosmos de Aragón (ceFca), Pl San Juán 1, 44001, Teruel, Spain ,
Galindo-Guil, Francisco J.; Observatorio Astrofísico de Javalambre (OAJ), Centro de estudios de física del cosmos de Aragón (ceFca), Pl San Juán 1, 44001, Teruel, Spain ,
González, Hugo; Observatorio de Forcarei FC3 Fundación Ceo, Ciencia e Cultura, Edif. CC. Experimentais Campus Lagoas-Marcosende, 36310, Vigo, Spain
Gonçalves, Rui; Plan Occult, Tomar, Portugal,
Rengstorf, Adam; Department of Chemistry and Physics, Purdue University Northwest, Hammond Campus 2200 169th St, 46323, Hammond, IN, USA
Flynn, Randy; Squirrel Valley Observatory, 3870 River Rd, 28722-6767, Columbus, NC, USA,
Olsen, Aart; International Occultation Timing Association (IOTA), 16348 E Glenbrook Blvd, 85268-2206, Fountain Hills, AZ, USA
Hanna, Bill; International Occultation Timing Association (IOTA), 16348 E Glenbrook Blvd, 85268-2206, Fountain Hills, AZ, USA
Barnes, Jason; Department of Physics, University of Idaho, 875 Perimeter Dr, 83844, Moscow, ID, USA
A'Hearn, Joseph A.; Department of Physics, University of Idaho, 875 Perimeter Dr, 83844, Moscow, ID, USA ,
Kreyche, Steven M.; Department of Physics, University of Idaho, 875 Perimeter Dr, 83844, Moscow, ID, USA
Miller, William J.; Department of Physics, University of Idaho, 875 Perimeter Dr, 83844, Moscow, ID, USA
Mortensen, Lillian E.; Department of Physics, University of Idaho, 875 Perimeter Dr, 83844, Moscow, ID, USA
Gibson, Thomas C.; Department of Physics, University of Idaho, 875 Perimeter Dr, 83844, Moscow, ID, USA
Walker, Gary; Loines Observatory, Maria Mitchell Association, Nantucket's Science Center, 2 Vestal Street, 02554, Nantucket, MA, USA
Stolle-McAllister, Gerogia; Loines Observatory, Maria Mitchell Association, Nantucket's Science Center, 2 Vestal Street, 02554, Nantucket, MA, USA ,
Feiden, Gregory A.; Department of Physics, University of North Georgia, 82 College Cir, 30597, Dahlonega, GA, USA ,
Froetschel, Joseph; Department of Physics, University of North Georgia, 82 College Cir, 30597, Dahlonega, GA, USA
Steel, Suzanne; Department of Physics, University of North Georgia, 82 College Cir, 30597, Dahlonega, GA, USA
Encardes, Destin; Department of Physics, University of North Georgia, 82 College Cir, 30597, Dahlonega, GA, USA
Fisher, R. Scott; University of Oregon, Deptartment of Physics, 1371 E 13th Ave, 97403, Eugene, OR, USA ,
Luken, Alton; University of Oregon, Deptartment of Physics, 1371 E 13th Ave, 97403, Eugene, OR, USA
Holcomb, Eric; University of Oregon, Deptartment of Physics, 1371 E 13th Ave, 97403, Eugene, OR, USA
Caton, Daniel; Department of Physics and Astronomy, Appalachian State University, 231 Garwood Hall 525 Rivers Street Boone, 28608-2106, Boone, NC, USA ,
Dunford, Bob; International Occultation Timing Association (IOTA), 16348 E Glenbrook Blvd, 85268-2206, Fountain Hills, AZ, USA,
Monin, Dmitry; National Research Council, Herzberg Astrononomy and Astrophysics Research Centre, 5071 West Saanich Road, Victoria, BC, Canada
Brown ME et al. Keck observatory laser guide star adaptive optics discovery and characterization of a satellite to the large kuiper belt object 2003 EL61 Astrophys. J. 2005 632 L45 L48
Leinhardt Zoë Marcus Robert Stewart Sarah The formation of the collisional family around the dwarf planet Haumea Astrophys. J. 2010 714 1789 1799
Proudfoot Benjamin Ragozzine Darin The formation of Haumea and its family via binary merging Nat. Commun. 2022 13 1:CAS:528:DC%2BB38XhtFGgtbzM 35477701 9046388 2262
Ragozzine D Brown ME Orbits and Masses of the Satellites of the Dwarf Planet Haumea (2003 EL61) Astron. J. 2009 137 4766 4776
Ortiz JL et al. The size, shape, density and ring of the dwarf planet Haumea from a stellar occultation Nature 2017 550 219 223 1:STN:280:DC%2BC1M%2FpslGlsg%3D%3D 29022593
Hastings Danielle et al. The Short Rotation Period of Hi’iaka, Haumea’s Largest Satellite Astron. J. 2016 152 195
Barkume KM Brown ME Schaller EL Water Ice on the Satellite of Kuiper Belt Object 2003 EL61 Astrophys. J. 2006 640 L87 L89
Fraser WC Brown ME NICMOS photometry of the unusual dwarf planet Haumea and its satellites Astrophys. J. 2009 695 L1 L3 1:CAS:528:DC%2BD1MXmvFarur4%3D
Vara-Lubiano, M. et al. The first multichord stellar occultation by the trans-Neptunian Binary (82075) 2000 YW134. In Europlanet Science Congress, EPSC2022-1048 (2022).
Jehin E et al. TRAPPIST: TRAnsiting Planets and PlanetesImals Small Telescope Messenger 2011 145 2 6
Magnusson P Distribution of spin axes and senses of rotation for 20 large asteroids Icarus 1986 68 1 39
Proudfoot Benjamin et al. Beyond Point Masses. III. Detecting Haumea’s Non-spherical Gravitational Field Planet. Sci. J. 2024 5 69
Masiero JR Wright EL Mainzer AK Uncertainties on Asteroid Albedos Determined by Thermal Modeling Planet. Sci. J. 2021 2 32
Müller, T. et al. Trans-Neptunian objects and Centaurs at thermal wavelengths. In Dina Prialnik, Maria Antoinetta Barucci, and Leslie Young, editors, The Trans-Neptunian Solar System, 153–181. (Elsevier, 2020).
Ortiz JL et al. Rotational fission of trans-Neptunian objects: the case of Haumea Mon. Not. R. Astron. Soc. 2012 419 2315 2324
Noviello JL Desch SJ Neveu Marc Proudfoot BCN Sonnett S Let It Go: Geophysically Driven Ejection of the Haumea Family Members Planet. Sci. J. 2022 3 225
Campo Bagatin A Benavidez PG Ortiz JL Gil-Hutton R On the genesis of the Haumea system Mon. Not. R. Astron. Soc. 2016 461 2060 2067
Pinilla-Alonso N et al. The surface of (136108) Haumea (2003 EL61), the largest carbon-depleted object in the trans-Neptunian belt Astron. Astrophys. 2009 496 547 556 1:CAS:528:DC%2BD1MXlsFWqsr8%3D
Müller T et al. Haumea’s thermal emission revisited in the light of the occultation results Icarus 2019 334 39 51
Dumas C Carry B Hestroffer D Merlin F High-contrast observations of (136108) Haumea Astron. Astrophys. 2011 528 A105
Buratti, B. J. et al. Spectral Analyses of Saturn’s Moons Using the Cassini Visual Infrared Mapping Spectrometer. In Janice L. Bishop, III Bell, James F., and Jeffrey E. Moersch, editors, Remote Compositional Analysis: Techniques for Understanding Spectroscopy, Mineralogy, and Geochemistry of Planetary Surfaces, 428–441. (Cambridge University Press, 2019).
Verbiscer Anne et al. Enceladus: Cosmic Graffiti Artist Caught in the Act Science 2007 315 815 1:CAS:528:DC%2BD2sXhsVShsr0%3D 17289992
Loveless S et al. On the Structure and Long-term Evolution of Ice-rich Bodies Astrophys. J. 2022 927 178
Csaba K et al. The mass and density of the dwarf planet (225088) 2007 OR10 Icarus 2019 334 3 10
Schlichting HE Sari R The Creation of Haumea’s Collisional Family Astrophys. J. 2009 700 1242 1246
Chandrasekhar, S. Ellipsoidal figures of equilibrium. The Silliman Foundation Lectures. (Yale University Press, 1969).
Vara-Lubiano M et al. The multichord stellar occultation on 2019 October 22 by the trans-Neptunian object (84922) 2003 VS2 Astron. Astrophys. 2022 663 17
Gaia Collaboration et al. Gaia Early Data Release 3. Summary of the contents and survey properties Astron. Astrophys. 2021 649 A1
Ortiz, J. L., Sicardy, B., Camargo, J. I. B., Santos-Sanz, P. & Braga-Ribas, F. Stellar occultation by TNOs: from predictions to observations. In Dina Prialnik, Maria Antoinetta Barucci, and Leslie Young, editors, The Trans-Neptunian Solar System, 413–437. (Elsevier, 2020).
Peng, Q. Y. et al. CCD astrometric measurements for the dwarf planet Haumea by ground-based telescopes. Astron. Astrophys.672, A61 (2023).
Gomes DCH et al. Can the Gravitational Effect of Planet X be Detected in Current era Tracking of the Known Major and Minor Planets? Planet. Sci. J. 2023 4 21
Rommel FL et al. Stellar occultations enable milliarcsecond astrometry for Trans-Neptunian objects and Centaurs Astron. Astrophys. 2020 644 A40
Stetson PB DAOPHOT: a computer program for crowded-field stellar photometry Pub. Astron. Soc. Pacific 1987 99 191
Gomes-Júnior, A. R. et al. SORA: Stellar Occultation Reduction and Analysis. Mon. Not. R. Astron. Soc. 511, 1167–1181 (2022).
Anderson B PyMovie - A Stellar-Occultation Aperture-Photometry Program J. Occ. Astron. 2019 9 9 13
Roques, F., Moncuquet, M. & Sicardy, B. Stellar occultations by small bodies - Diffraction effects. Astron. J.93, 1549–1558 (1987).
Delrez, L. et al. SPECULOOS: a network of robotic telescopes to hunt for terrestrial planets around the nearest ultracool dwarfs. In Heather K. Marshall and Jason Spyromilio, editors, Ground-based and Airborne Telescopes VII, volume 10700 of Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, 107001I (2018).
Mommert M Photometrypipeline: An automated pipeline for calibrated photometry Astron. Comput. 2017 18 47 53
Fernández-Valenzuela E et al. The Changing Rotational Light-curve Amplitude of Varuna and Evidence for a Close-in Satellite Astropys. J. 2019 883 L21
Fernández-Valenzuela E Ortiz JL Duffard R Santos-Sanz P Morales N 2008 OG19: a highly elongated Trans-Neptunian object Mon. Not. R. Astron. Soc. 2016 456 2354 2360
Lellouch E et al. The thermal lightcurve of (136108) Haumea Astro. Astrophys. 2010 518 L147
Lomb NR Least-squares frequency analysis of unequally spaced data Astrophys. Space Sci. 1976 39 447 462
Zechmeister M Kürster M The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms Astron. Astrophys. 2009 496 577 584
Virtanen P et al. SciPy 1.0: fundamental algorithms for scientific computing in python Nat. Methods 2020 17 261 272 1:CAS:528:DC%2BB3cXislCjuro%3D 32015543 7056644
Rommel FL et al. A large topographic feature on the surface of the trans-Neptunian object (307261) 2002 MS4 measured from stellar occultations Astron. Astrophys. 2023 678 25
Farinella P Paolicchi P Tedesco EF Zappala V Triaxial equilibrium ellipsoids among the asteroids? Icarus 1981 46 114 123
Fernández-Valenzuela, E. et al. Hi’iaka’s physical and dynamical properties using long-term photometric data. In Europlanet Science Congress, EPSC2022–406 (2022).
Gourgeot F et al. Near-infrared spatially resolved spectroscopy of (136108) Haumea’s multiple system Astron. Astrophys. 2016 593 A19
Pedro L Time-resolved near-infrared photometry of extreme Kuiper belt object Haumea Astron. J. 2009 137 3404 3413
Lockwood AC Brown ME Stansberry J The Size and Shape of the Oblong Dwarf Planet Haumea Earth Moon Planets 2014 111 127 137 1:CAS:528:DC%2BC2cXotFeltbk%3D
Zacharias, N. et al. VizieR Online Data Catalog: UCAC4 Catalogue (Zacharias +, 2012). VizieR Online Data Catalog, page I/322 A (2012).
van Belle GT Predicting Stellar Angular Sizes Pub. Astron. So. Pacific 1999 111 1515 1523
