|Discovery site||Deep Ecliptic Survey at Kitt Peak|
|Discovery date||August 25, 2003 and
July, 2006 (secondary)
|MPC designation||(385446) Manwë|
4:7 resonance (DES)
|Epoch May 23, 2014 (JD 2456800.5)|
|288.25 a (105,281 d)|
|Dimensions||≈58–92 (primary) and 33–53 km (secondary)|
secondary's magnitude difference with primary's: 0.6 to 2.1 (variable)
385446 Manwë [ˈmanwe] is a resonant binary Kuiper belt object in a 4:7 mean-motion resonance with Neptune. The secondary, Thorondor, is estimated to be about half the size of the primary, 33–53 km vs. 58–92 km. The light curve has considerable photometric variability, with the relative magnitude of the two objects measured variously from 0.6–2.1 over the course of a few years.
Manwë and Thorondor are predicted to be going through a period of mutual occultations and transits from 2014–2018, where one object crosses in front of the other as seen from Earth. Pluto and Charon went through a similar series of mutual events from 1985–1990. Observations of these events will allow for better estimates of the radii of the two objects and their densities, as well as possibly determining their shapes and mapping surface color and albedo features. The first event, an inferior occultation, is predicted for 2014 July 16, and they continue until 2018 October 25.
The composition of Manwë is unknown but likely to be mostly ice, because the nominal density (with large uncertainty) is less than that of water. At least one other Kuiper belt object, (55637) 2002 UX25, has been found with a density of less than 1 g/cm3, which implies an object made mostly of ice with a low rock fraction and high porosity.
The satellite's orbit has the following parameters: semi-major-axis, 6674 ± 41 km; period, 110.176 ± 0.018 days; eccentricity, 0.5632 ± 0.0070; and inclination, 25.58 ± 0.23°. The total system mass is about 1.941 × 1018 kg.
The object was named after Manwë, the fictional king of the Valar in J. R. R. Tolkien's Middle-earth legendarium. Manwë is foremost among the deities who rule the world. Manwë takes special responsibility for the air and winds. Thorondor is the Lord of Eagles in the First Age in Tolkien's writing.
- "JPL Small-Body Database Browser: 385446 Manwë (2003 QW111)". 2013-04-23 last obs. Retrieved 2014-04-23. Check date values in:
- Johnston's Archive on (385446) Manwë Retrieved 2014-04-23
- Marc W. Buie. "Orbit Fit and Astrometric record for 385446". SwRI (Space Science Department). Retrieved 2014-04-23.
- Grundy, W.M.; Benecchi, S.D.; Porter, S.B.; Noll, K.S. (2014). "The Orbit of Transneptunian Binary Manwë and Thorondor and their Upcoming Mutual Events" (PDF). Icarus. In press. doi:10.1016/j.icarus.2014.04.021.
- Manwë - Thorondor Mutual Events
- Brown, M. E. (2013). "The density of mid-sized Kuiper belt object 2002 UX25 and the formation of the dwarf planets". The Astrophysical Journal Letters 778 (2). arXiv:1311.0553. doi:10.1088/2041-8205/778/2/l34.