The size, shape, density and ring of the dwarf planet Haumea from a stellar occultation


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Ortiz J. L. , SANTOS-SANZ P., SICARDY B., BENEDETTI-ROSSI G., BERARD D., MORALES N., et al.

NATURE, cilt.550, ss.219-0, 2017 (SCI İndekslerine Giren Dergi) identifier identifier identifier

  • Cilt numarası: 550 Konu: 7675
  • Basım Tarihi: 2017
  • Doi Numarası: 10.1038/nature24051
  • Dergi Adı: NATURE
  • Sayfa Sayısı: ss.219-0

Özet

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Haumea—one of the four known trans-Neptunian dwarf planets—
is a very elongated and rapidly rotating body1–3. In contrast to
other dwarf planets4–6, its size, shape, albedo and density are not
well constrained. The Centaur Chariklo was the first body other
than a giant planet known to have a ring system7, and the Centaur
Chiron was later found to possess something similar to Chariklo’s
rings8,9. Here we report observations from multiple Earth-based
observatories of Haumea passing in front of a distant star (a multichord
stellar occultation). Secondary events observed around the
main body of Haumea are consistent with the presence of a ring with
an opacity of 0.5, width of 70 kilometres and radius of about 2,287
kilometres. The ring is coplanar with both Haumea’s equator and the
orbit of its satellite Hi’iaka. The radius of the ring places it close to
the 3:1 mean-motion resonance with Haumea’s spin period—that is,
Haumea rotates three times on its axis in the time that a ring particle
completes one revolution. The occultation by the main body provides
an instantaneous elliptical projected shape with axes of about 1,704
kilometres and 1,138 kilometres. Combined with rotational light curves, the occultation constrains the three-dimensional orientation
of Haumea and its triaxial shape, which is inconsistent with a
homogeneous body in hydrostatic equilibrium. Haumea’s largest axis
is at least 2,322 kilometres, larger than previously thought, implying
an upper limit for its density of 1,885 kilograms per cubic metre and a
geometric albedo of 0.51, both smaller than previous estimates1,10,11.
In addition, this estimate of the density of Haumea is closer to that
of Pluto than are previous estimates, in line with expectations. No
global nitrogen- or methane-dominated atmosphere was detected.