Ilmarë
Ilmarë, or Varda I, full designation 174567 Varda I Ilmarë, is the single known natural satellite of the Kuiper belt object 174567 Varda. It was discovered by Keith Noll et al. in 2009, at a separation of about 0.12 arcsec, using discovery images taken by the Hubble Space Telescope on 26 April 2009, and reported in 2011. At approximately 326 km in diameter (about 45% that of its primary), it is the fourth or fifth-largest known moon of a trans-Neptunian object, after Pluto I Charon, Eris I Dysnomia, Orcus I Vanth and very possibly Haumea I Hiʻiaka. Assuming that Ilmarë has the same albedo and density as Varda, Ilmarë would constitute approximately 8.4% of the system's mass, approximately 2.2×1019 kg.
Hubble Space Telescope image of Varda and its satellite Ilmarë, taken in 2010 and 2011 | |
| Discovery | |
|---|---|
| Discovered by | Keith S. Noll et al. |
| Discovery date | 2009, based on images taken on 2009 April 26 |
| Designations | |
Designation | Varda I |
| Pronunciation | /ˈɪlməriː/ |
Named after | Ilmarë (figure by J. R. R. Tolkien) |
Alternative names | 174567 Varda I Ilmarë |
| Adjectives | Ilmarëan /ɪlməˈriːən/ |
| Orbital characteristics | |
Semi-major axis | 4809±39 km |
| Eccentricity | 0.0181±0.0045 or 0.0247±0.0048 (0.0215±0.0080 adopted) |
Orbital period (sidereal) | 5.75058±0.00015 d |
| Inclination | 101.0±1.9 or 85.1±1.8 |
| Satellite of | Varda |
| Physical characteristics | |
Mean diameter | ≈356 326+38 −34 km |
| Mass | ≈2.2×1019 kg |
Mean density | 1.24+0.50 −0.35 g/cm3 (system) |
| Albedo | ≈0.085 0.166+0.043 −0.033 (assuming same as Varda) |
Spectral type | B−V = 0.857±0.061 V−I = 1.266±0.052 |
| 3.097±0.060 | |
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