astro.wikisort.org - Asteroid

Polana (minor planet designation: 142 Polana) is a very dark asteroid from the asteroid belt. It was discovered by Johann Palisa on January 28, 1875, and named after the city of Pola (now Pula, Croatia), home of the Austrian Naval Observatory where he made the discovery.[1]

142 Polana

Polana is in a 1:2 resonance with Mars
Discovery[1]
Discovered by	J. Palisa
Discovery site	Austrian Naval Obs.
Discovery date	28 January 1875
Designations
MPC designation	(142) Polana
Pronunciation	[citation needed]
Named after	Pula
Alternative designations	A875 BA; 1923 WA; 1954 BH; 1956 XZ; 1963 SA
Minor planet category	Asteroid belt
Orbital characteristics[1]
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc	117.65 yr (42971 d)
Aphelion	2.7444 AU (410.56 Gm)
Perihelion	2.0934 AU (313.17 Gm)
Semi-major axis	2.4189 AU (361.86 Gm)
Eccentricity	0.13457
Orbital period (sidereal)	3.76 yr (1374.1 d)
Average orbital speed	19.07 km/s
Mean anomaly	140.92°
Mean motion	0° 15m 43.128s / day
Inclination	2.2379°
Longitude of ascending node	291.27°
Argument of perihelion	292.00°
Physical characteristics
Dimensions	55.29±1.6 km[1] 55.3 ± 1.6[2]
Synodic rotation period	9.764 h (0.4068 d)
Geometric albedo	0.0451±0.003[1] 0.045 ± 0.003[2]
Spectral type	F/B[1] B−V=0.621±0.022[1] U−B=0.236±0.035[1]
Absolute magnitude (H)	10.27[1]

It is a major member of the eponymously named Polana family, which is a subgroup of the Nysa family.[3] The asteroid has an estimated diameter of about 55.3 km and a low albedo of 0.045.[2] It is orbiting at a distance of 2.419 times the separation of the Earth from the Sun, with an orbital period of 3.76 years and an eccentricity of 0.14.

In the Tholen classification scheme, Polana is a primitive carbonaceous asteroid of type F, which is a subdivision of more common C-type.[1] Under the SMASS classification taxonomy, Polana is listed as a B-type asteroid; a group that combines both the Tholen B and F types. The spectrum of this object suggests the presence of magnetite (Fe₃O₄), which gives it the spectrally blue coloration that is a characteristic of this SMASS class.[4]

Mars resonance

Polana is in a 1:2 orbital resonance with Mars, meaning that Polana orbits the Sun once for every two orbits that Mars completes. This resonance helps protect the asteroid from orbital erosion: the orbital eccentricities of the resonant asteroids are clearly greater than the non-resonant asteroids. There is a peak in the number of asteroids located at 2.419 AU from the Sun.[6] In spite of strong perturbations caused by the passing of both Jupiter and Mars, the 1:2 Mars resonance brings about stability for billions of years. There are up to 1,500 asteroids in this resonance, and the resonance between Polana and Mars will strengthen over the next million years due to Polana transitioning into a strong libration period with Mars.[7]

References

External links

• Asteroids inside the resonance 1:2 with Mars, Tabaré Gallardo
• 142 Polana at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 142 Polana at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters

На других языках

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[de] (142) Polana

(142) Polana ist ein Asteroid des Asteroiden-Hauptgürtels, der am 28. Januar 1875 von Johann Palisa entdeckt wurde. Palisa entdeckte den Asteroiden an der Marinesternwarte von Pula (it. Pola) und benannte ihn nach diesem Ort.

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- [en] 142 Polana

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[es] (142) Polana

(142) Polana es un asteroide perteneciente al cinturón de asteroides descubierto el 28 de enero de 1875 por Johann Palisa desde el observatorio de Pula, Croacia.[2] Está nombrado por el lugar del descubrimiento.[3]

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[fr] (142) Polana

(142) Polana est un astéroïde de la ceinture principale découvert par Johann Palisa le 28 janvier 1875.

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[ru] (142) Пулана

(142) Пулана (нем. Polana) — является довольно большим и очень тёмным астероидом главного пояса, принадлежащим к редкому спектральному классу F. Он был открыт 28 января 1875 года австрийским астрономом Иоганном Пализой в обсерватории Пула и назван в честь австрийского города Пула, вблизи которого она находится[1]. Он является одним из главных представителей семейства Нисы[2].

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