Asteroid 809 Lundia (apparent magnitude 16.6) near a mag 15.6 star.
|Discovered by||Max Wolf|
|Discovery date||August 11, 1915|
|1915 XP; 1936 VC|
|Minor planet category||Main belt|
|Epoch November 26, 2005 (JD 2453700.5)|
|Aphelion||407.368 Gm (2.723 AU)|
|Perihelion||275.743 Gm (1.843 AU)|
|341.556 Gm (2.283 AU)|
|1260.094 d (3.45 a)|
Average orbital speed
|Dimensions||10.26 ± 0.07 km|
|Mass||(9.27 ± 3.09) × 1014 kg|
|1.64 ± 0.10 g/cm3|
|0.001–0.003 m/s² (estimate)|
|0.003–0.005 km/s (estimate)|
max: 260-280 K
Lundia orbits within the Flora family. However, its V-type spectrum indicates that it is not genetically related to the Flora family, but rather is probably a fragment (two fragments if one includes its moon) ejected from the surface of 4 Vesta by a large impact in the past. Its orbit lies too far from Vesta for it to actually be a member of the Vesta family. It is not clear how it arrived at an orbit so far from Vesta, but other examples of V-type asteroids orbiting fairly far from their parent body are known. A mechanism of interplay between the Yarkovsky effect and nonlinear secular resonances (primarily involving Jupiter and Saturn) has been proposed.
Lightcurve observations in 2005 revealed that Lundia is a binary system of two similarly sized objects orbiting their common centre of gravity. "Lundia" now refers to one of the objects, the other being provisionally designated S/2005 (809) 1. The similarity of size between the two components is suspected because during mutual occultations the brightness drops by a similar amount independently of which component is hidden. Due to the similar size of the primary and secondary the Minor Planet Center lists this as a binary companion.
Assuming an albedo similar to 4 Vesta (around 0.4) suggests that the components are about 7 km across. They orbit each other in a period of 15.4 hours, which roughly indicates that the separation between them is very close: to the order of 10–20 km if typical asteroid albedo and density values are assumed.
- Carry, B. (December 2012), Density of asteroids, Planetary and Space Science 73: 98-118, arXiv:1203.4336, Bibcode:2012P&SS...73...98C, doi:10.1016/j.pss.2012.03.009. See Table 1.
- M. Florczak, D. Lazarro, & R. Duffard (2002). "Discovering New V-Type Asteroids in the Vicinity of 4 Vesta". Icarus 159: 178–182. Bibcode:2002Icar..159..178F. doi:10.1006/icar.2002.6913.
- V. Carruba et al. (2005). "On the V-type asteroids outside the Vesta family". Astronomy & Astrophysics 441 (2): 819–829. arXiv:astro-ph/0506656. Bibcode:2005A&A...441..819C. doi:10.1051/0004-6361:20053355.
- Poznań observatory  (Lightcurve showing signature of the binary)
- "Satellites and Companions of Minor Planets". IAU / Central Bureau for Astronomical Telegrams. Retrieved 2011-07-03.
- Electronic Telegram No. 239 announcing the binary system (2005 October 1)
- Discovery Circumstances: Numbered Minor Planets
- Johnston Archive entry for 809 Lundia
- Lightcurve showing signature of the binary