142 Polana

Main-belt asteroid February 2012 yes #D6D6D6 142 Polana Polana-Mars2013.gif Polana's orbit, showing its 1:2 resonance with Mars J. Palisa Austrian Naval Obs. 28 January 1875 (142) Polana A875 BA; 1923 WA;1954 BH; 1956 XZ;1963 SA March 2020 Pula Asteroid belt 117.65 yr (42971 d) 0 31 July 2016 (JD 2457600.5) 2.7444 AU Gm on on 2.0934 AU Gm on 2.4189 AU Gm on 0.13457 3.76 yr (1374.1 d) 140.92° 0.26198 ms / day 2.2379° 291.27° 292.00° 19.07 km/s 55.29 1.6 km55.3 ± 1.6 F/BB−V=0.621±0.022U−B=0.236±0.035 0.0451 0.0030.045 ± 0.003 9.764 h d on on 10.27 142 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. It is the largest member of the eponymously named New Polana family, an family of dark, carbonaceous asteroids in the Nysa–Polana complex. The asteroid has an estimated diameter of about 55.3 km and a low albedo of 0.045. 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. 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. thumb|left|Origin of 162173 Ryugu may be either 495 Eulalia or 142 PolanaThe geomorphology, color, and thermal properties of Ryugu: Implications for parent-body processes Science 364 6437 eaaw0422 S. Sugita etal 19 Mar 2019 10.1126/science.aaw0422 30890587 7370239 2019Sci...364..252S 1893/29363 free Yellow Sun RoyalBlue EarthLime 162173 RyuguOrangeRed 142 PolanaCyan 495 Eulalia 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. 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. References 30em 14 August 2007 142 Polana JPL Small-Body Database Browser https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=Polana 12 May 2016 Lazzarin M. Barbieri C. Barucci M. A. Visible Spectroscopy of Dark, Primitive Asteroids Astronomical Journal 110 3058 10.1086/117747 1995AJ....110.3058L December 1995 free 2007 A new population of asteroids: the resonants 1:2 with Mars Institute of Physics, Faculty of Sciences Montevideo, Uruguay Tabaré Gallardo http://www.fisica.edu.uy/~gallardo/marte12/mars1to2.html December 17, 2009 A New Dynamical Population of Asteroids Revista Mexicana de Astronomía y Astrofísica, Serie de Conferencias 35 21–22 2009 Tabaré Gallardo 2009RMxAC..35...21G http://www.astroscu.unam.mx/rmaa/RMxAC..35/PDF/RMxAC..35_tgallardo.pdf December 17, 2009 Yang Bin Jewitt David Identification of Magnetite in B-type Asteroids The Astronomical Journal 140 3 692–698 10.1088/0004-6256/140/3/692 2010AJ....140..692Y 1006.5110 September 2010 724871 Dykhuis Melissa J. Greenberg Richard Collisional family structure within the Nysa–Polana complex Icarus May 2015 252 199–211 10.1016/j.icarus.2015.01.012 1501.04649 2015Icar..252..199D External links Asteroids inside the resonance 1:2 with Mars, Tabaré Gallardo 142 141 Lumen 142 143 Adria 000142 Category:Discoveries by Johann Palisa Category:Named minor planets Category:Mars 000142 000142 18750128