The mutual orbit, mass, and density of the large transneptunian binary system Varda and Ilmarë

2015/05/04 by W. M. Grundy, Simon B. Porter, S. B. Porter +15 · 1 citation
Physics and Astronomy · #Aerospace engineering #Asteroid #Astro and Planetary Science #Astronomy #Astrophysics #Circular orbit #High mass #Orbit (dynamics) #Physics #Planetary Science and Exploration #Satellite #Spitzer Space Telescope #Stellar, planetary, and galactic studies #Telescope #astro-ph.EP

paper · pdf · doi:10.1016/j.icarus.2015.04.036

16 pages, 4 tables, 6 figures, in press in Icarus

arxiv created 2015/05/04 · openalex publication_date 2015/05/12 · arxiv updated 2015/06/03 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

From observations by the Hubble Space Telescope, Keck II Telescope, and Gemini North Telescope, we have determined the mutual orbit of the large transneptunian object (174567) Varda and its satellite Ilmarë. These two objects orbit one another in a highly inclined, circular or near-circular orbit with a period of 5.75 days and a semimajor axis of 4810 km. This orbit reveals the system mass to be (2.664 +/- 0.064) x 10²0 kg, slightly greater than the mass of the second most massive main-belt asteroid (4) Vesta. The dynamical mass can in turn be combined with estimates of the surface area of the system from Herschel Space Telescope thermal observations to estimate a bulk density of 1.24 +0.50 -0.35 g cm^-3. Varda and Ilmarë both have colors similar to the combined colors of the system, B-V = 0.886 +/- 0.025 and V-I = 1.156 +/- 0.029.

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• Interpreting the densities of the Kuiper belt's dwarf planets