1473 Ounas

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1473 Ounas
Discovery [1]
Discovered byY. Väisälä
Discovery siteTurku Obs.
Discovery date22 October 1938
MPC designation(1473) Ounas
Named after
Ounasjoki River
(in Finland)[2]
1938 UT · 1950 NZ
1950 PB1
main-belt · (middle)[3]
Orbital characteristics[1]
Epoch 16 February 2017 (JD 2457800.5)
Uncertainty parameter 0
Observation arc77.90 yr (28,452 days)
Aphelion3.1862 AU
Perihelion1.9623 AU
2.5743 AU
4.13 yr (1,509 days)
0° 14m 18.96s / day
Physical characteristics
Dimensions17.62 km (derived)[3]
20.032 km (dated)[5]
16 h (dated)[3]
139.1±0.1 h[6]
139.1±0.5 h[7]
0.0841 (dated)[5]
0.1189 (derived)[3]
11.67±0.32[8] · 11.7[1][3] · 11.8[5]

1473 Ounas, provisional designation 1938 UT, is a stony asteroid, suspected tumbler and a slow rotator from the middle region of the asteroid belt, approximately 18 kilometers in diameter. It was discovered on 22 October 1938, by Finnish astronomer Yrjö Väisälä at Turku Observatory in Southwest Finland.[9] The asteroid was named after the Finnish Ounas river.[2]

Classification and orbit[edit]

Ounas is a S-type asteroid that orbits the Sun in the central main-belt at a distance of 2.0–3.2 AU once every 4 years and 2 months (1,509 days). Its orbit has an eccentricity of 0.24 and an inclination of 14° with respect to the ecliptic.[1] As no precoveries were taken, and no previous identifications were made, the body's observation arc begins with its official discovery observation at Turku in 1938.[9]

Physical characteristics[edit]

In October 2012/13, a rotational lightcurve of Ounas was obtained from photometric observations by astronomers René Roy, Vladimir Benishek, Andrea Ferrero, Daniel Klinglesmith, Frederick Pilcher, Raoul Behrend and Petr Pravec. It gave a well-defined rotation period of 139.1 hours with a brightness variation of 0.6 magnitude (U=3/3).[6][7] Ounas is a suspected "tumbler", which have a non-principal axis rotation (NPAR).[6]

According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, the asteroid measures 18.16 kilometers in diameter and its surface has an albedo of 0.11.[4][5] The Collaborative Asteroid Lightcurve Link derives an albedo of 0.1189 and a diameter of 17.62 kilometers with an absolute magnitude of 11.7.[3]


This minor planet was named after the Ounas river, one of the principal rivers in Finland.[2] The official naming citation was published before November 1977 (M.P.C. 3928).[10]


  1. ^ a b c d "JPL Small-Body Database Browser: 1473 Ounas (1938 UT)" (2016-11-05 last obs.). Jet Propulsion Laboratory. Retrieved 16 December 2016.
  2. ^ a b c Schmadel, Lutz D. (2007). Dictionary of Minor Planet Names – (1473) Ounas. Springer Berlin Heidelberg. p. 118. ISBN 978-3-540-00238-3. Retrieved 16 December 2016.
  3. ^ a b c d e f g "LCDB Data for (1473) Ounas". Asteroid Lightcurve Database (LCDB). Retrieved 16 December 2016.
  4. ^ a b c Masiero, Joseph R.; Grav, T.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; et al. (August 2014). "Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos". The Astrophysical Journal. 791 (2): 11. arXiv:1406.6645. Bibcode:2014ApJ...791..121M. doi:10.1088/0004-637X/791/2/121. Retrieved 16 December 2016.
  5. ^ a b c d Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results" (PDF). The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90. Retrieved 16 December 2016.
  6. ^ a b c Pilcher, Frederick; Benishek, Vladimir; Ferrero, Andrea; Klinglesmith, Daniel A., III; Pravec, Petr; Roy, Rene; et al. (July 2013). "New Photometry of 1473 Ounas". The Minor Planet Bulletin. 40 (3): 126–129. Bibcode:2013MPBu...40..126P. ISSN 1052-8091. Retrieved 16 December 2016.
  7. ^ a b Behrend, Raoul. "Asteroids and comets rotation curves – (1473) Ounas". Geneva Observatory. Retrieved 16 December 2016.
  8. ^ Veres, Peter; Jedicke, Robert; Fitzsimmons, Alan; Denneau, Larry; Granvik, Mikael; Bolin, Bryce; et al. (November 2015). "Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 - Preliminary results". Icarus. 261: 34–47. arXiv:1506.00762. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. Retrieved 16 December 2016.
  9. ^ a b "1473 Ounas (1938 UT)". Minor Planet Center. Retrieved 16 December 2016.
  10. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 16 December 2016.

External links[edit]