809 Lundia

809 Lundia

Asteroid 809 Lundia (apparent magnitude 16.6) near a mag 15.6 star
Discovery
Discovered by	Max Wolf
Discovery date	11 August 1915
Designations
MPC designation	(809) Lundia
Pronunciation	/ˈlʌndiə/
Named after	Lund Observatory
Alternative designations	1915 XP; 1936 VC
Minor planet category	Main belt
Orbital characteristics[1]
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc	100.48 yr (36700 d)
Aphelion	2.72316 AU (407.379 Gm)
Perihelion	1.84193 AU (275.549 Gm)
Semi-major axis	2.28254 AU (341.463 Gm)
Eccentricity	0.19304
Orbital period (sidereal)	3.45 yr (1259.6 d)
Mean anomaly	76.7867°
Mean motion	0° 17^m 8.912^s / day
Inclination	7.14911°
Longitude of ascending node	154.580°
Argument of perihelion	196.162°
Physical characteristics
Dimensions	10.26 ± 0.07 km[2]
Mass	(9.27 ± 3.09) × 10^14 kg[2]
Mean density	1.64 ± 0.10 g/cm^3[2]
Synodic rotation period	15.4142 h (0.64226 d)
Spectral type	V
Absolute magnitude (H)	12.2

809 Lundia is a small, binary, V-type asteroid^[3] orbiting within the Flora family in the main belt. It is named after Lund Observatory, Sweden.

Characteristics

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.^[4]

Binary system

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.^[5] Due to the similar size of the primary and secondary the Minor Planet Center lists this as a binary companion.^[6]

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,^[5] 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.

References

1. "809 Lundia (1915 XP)". JPL Small-Body Database. NASA/Jet Propulsion Laboratory. Retrieved 4 May 2016.
2. 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.
3. 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.
4. 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.
5. Poznań observatory "Physical studies of asteroids at Poznan Observatory". Archived from the original on 2 July 2001. Retrieved 2 July 2001. (Lightcurve showing signature of the binary)
6. "Satellites and Companions of Minor Planets". IAU / Central Bureau for Astronomical Telegrams. Archived from the original on 21 January 2011. Retrieved 3 July 2011.

External links

• Electronic Telegram No. 239 announcing the binary system (2005 October 1)
• Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
• (809) Lundia, datasheet, johnstonsarchive.net
• Asteroids with Satellites, Robert Johnston, johnstonsarchive.net
• Lightcurve showing signature of the binary
• 809 Lundia at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 809 Lundia at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters