174567 Varda


174567 Varda is a binary trans-Neptunian object of the resonant hot classical population of the Kuiper belt, located in the outermost region of the Solar System. Its moon, Ilmarë, was discovered in 2009.
Brown estimates that, with an absolute magnitude of 3.5 and a calculated diameter of approximately, it is likely a dwarf planet.
However, Grundy et al. argue that objects such as Varda, in the size range of 400–1000 km, with albedos less than ≈0.2 and densities of ≈1.2 g/cm3 or less, have likely never compressed into fully solid bodies, let alone differentiated, and so are highly unlikely to be dwarf planets.

Discovery and orbit

Varda was discovered in March 2006, using imagery dated from June 21, 2003 by Jeffrey A. Larsen with the Spacewatch telescope as part of a United States Naval Academy Trident Scholar project.
It orbits the Sun at a distance of 39.5–52.7 AU once every 313.1 years. Its orbit has an eccentricity of 0.14 and an inclination of 21.5° with respect to the ecliptic., Varda is 47.5 AU from the Sun. It will come to perihelion in April 2094. It has been observed 321 times over 23 oppositions, with precovery images back to 1980.

Name

Names for Varda and its moon were announced on 16 January 2014. Varda is the queen of the Valar, creator of the stars, one of most powerful servants of almighty Eru Iluvatar in J. R. R. Tolkien's fictional mythology. Ilmarë is a chief of the Maiar and Varda's handmaiden.

Satellite

Varda has at least one satellite, Ilmarë, which was discovered in 2009. It is estimated to be about 350 km in diameter, constituting 8% of the system mass, or , assuming its density and albedo the same as that of Varda.
The Varda–Ilmarë system is tightly bound, with a semimajor axis of and an orbital period of 5.75 days.

Physical properties

Based on its apparent brightness and assumed albedo, the estimated combined size of the Varda–Ilmarë system is, with the size of the primary estimated at. The total mass of the binary system is approximately. The density of both the primary and the satellite is estimated at about assuming that they have equal density. On the other hand if the density or albedo of the satellite is lower than that of primary then the density of Varda will be higher up to.
On 10 September 2018, Varda's equatorial diameter was measured to be via a stellar occultation, with an oblateness of 0.085. The equivalent diameter is 756 km, consistent with previous measurements.
The surfaces of both the primary and the satellite appear to be red in the visible and near-infrared parts of the spectrum, with Ilmarë being slightly redder than Varda. The spectrum of the system does not show water absorption but shows evidence of methanol ice. The rotation period of Varda is estimated at 5.61 hours.