809 Lundia

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809 Lundia
Asteroid 809 Lundia (apparent magnitude 16.6) near a mag 15.6 star.
Discovered by Max Wolf
Discovery date August 11, 1915
Named after
Lund Observatory
1915 XP; 1936 VC
Main belt
Orbital characteristics
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)
Eccentricity 0.193
1260.094 d (3.45 a)
19.53 km/s
Inclination 7.143°
Physical characteristics
Dimensions 10.26 ± 0.07[1] km
Mass (9.27 ± 3.09) × 1014[1] kg
Mean density
1.64 ± 0.10[1] g/cm3
0.001–0.003 m/s² (estimate)
0.003–0.005 km/s (estimate)
Temperature 165-180 K
max: 260-280 K
Spectral type

809 Lundia is a small, binary, V-type asteroid[2] orbiting within the Flora family in the main belt. It is named after Lund Observatory, Sweden.


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 its moon is included) 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.[3]

Binary system[edit]

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.[4] Due to the similar size of the primary and secondary the Minor Planet Center lists this as a binary companion.[5]

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,[4] 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.


  1. ^ a b c Carry, B. (December 2012), "Density of asteroids", Planetary and Space Science 73, pp. 98–118, arXiv:1203.4336, Bibcode:2012P&SS...73...98C, doi:10.1016/j.pss.2012.03.009.  See Table 1.
  2. ^ 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. 
  3. ^ 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. 
  4. ^ a b Poznań observatory [1] (Lightcurve showing signature of the binary)
  5. ^ "Satellites and Companions of Minor Planets". IAU / Central Bureau for Astronomical Telegrams. Retrieved 2011-07-03. 

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