1845 Helewalda

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1845 Helewalda
Discovery [1]
Discovered by P. Wild
Discovery site Zimmerwald Obs.
Discovery date 30 October 1972
MPC designation (1845) Helewalda
Named after
Helen Gachnang
(friend of discoverer)[2]
1972 UC · 1931 VC1
1954 GG · 1971 OR
1971 QX2
main-belt · (outer)[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc 85.50 yr (31,229 days)
Aphelion 3.1371 AU
Perihelion 2.8001 AU
2.9686 AU
Eccentricity 0.0568
5.11 yr (1,868 days)
0° 11m 33.72s / day
Inclination 10.720°
Physical characteristics
Dimensions 19.930±0.377[5]
20.426±0.147 km[6]
32.03 km (calculated)[3]
7.2786±0.0002 h[7]
7.3985±0.0098 h[8]
7.399±0.004 h[9]
7.4±0.1 h[10]
0.057 (assumed)[3]
C (assumed)[3]
11.193±0.002[8] · 11.2[1][3] · 11.3[6] · 11.60±0.98[11]

1845 Helewalda, provisional designation 1972 UC, is a carbonaceous Eoan asteroid in the outer regions of the asteroid belt, approximately 20 kilometers in diameter. It was discovered by Swiss astronomer Paul Wild at Zimmerwald Observatory near Bern, Switzerland, on 30 October 1972.[12] The asteroid was named after Helen Gachnang, a friend of the discoverer.[2]

Orbit and classification[edit]

Helewalda is a member of the Eos family (606), the largest asteroid family in the outer main belt consisting of nearly 10,000 asteroids.[4][13]:23 It orbits the Sun in the outer main-belt at a distance of 2.8–3.1 AU once every 5 years and 1 month (1,868 days). Its orbit has an eccentricity of 0.06 and an inclination of 11° with respect to the ecliptic.[1] The first precovery was taken at Lowell Observatory in 1931, extending the asteroid's observation arc by 41 years prior to its discovery.[12]

Physical characteristics[edit]

Helewalda is an assumed carbonaceous C-type asteroid.[3]

Rotation period[edit]

Based on observations made by French astronomer René Roy in March 2010, Helewalda has a well-determined rotation period of 7.2786±0.0002 hours with a brightness variation of 0.26 in magnitude (U=3-).[7]

Between 2009 and 2015, other lightcurves were obtained at the Oakley Southern Sky Observatory in Australia (E09), the Via Capote Observatory at Thousand Oaks, California (G69), and the Palomar Transient Factory at Palomar Observatory. They gave a similar period of 7.399±0.004, 7.4±0.1 and 7.3985±0.0098 hours with a corresponding amplitude of 0.20, 0.28 and 0.15, respectively (U=2/2+/2).[9][10][8]

Diameter and albedo[edit]

The Collaborative Asteroid Lightcurve Link calculates a diameter of 32.0 kilometers, based on an assumed standard albedo for carbonaceous C-type asteroids of 0.057,[3] while the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer measured a higher albedo of 0.134 and 0.129 and a corresponding diameter of 19.9 and 20.4 kilometers in diameter, respectively.[5][6]


The discoverer, Paul Wild, named a pair of asteroids after two of his former schoolmates, Susi and Helen, both from the small village of Wald, Zürich in Switzerland. This one was dedicated to Helen Gachnang, while the previously numbered asteroid 1844 Susilva was given to Susi Petit-Pierre.[2][14] The official naming citation was published by the Minor Planet Center before November 1977 (M.P.C. 4156).[15]


  1. ^ a b c d "JPL Small-Body Database Browser: 1845 Helewalda (1972 UC)" (2017-05-05 last obs.). Jet Propulsion Laboratory. Retrieved 8 June 2017. 
  2. ^ a b c Schmadel, Lutz D. (2007). Dictionary of Minor Planet Names – (1845) Helewalda. Springer Berlin Heidelberg. p. 148. ISBN 978-3-540-00238-3. Retrieved 18 May 2016. 
  3. ^ a b c d e f g "LCDB Data for (1845) Helewalda". Asteroid Lightcurve Database (LCDB). Retrieved 18 May 2016. 
  4. ^ a b "Small Bodies Data Ferret". Nesvorny HCM Asteroid Families V3.0. Retrieved 21 November 2017. 
  5. ^ 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:1406.6645Freely accessible. Bibcode:2014ApJ...791..121M. doi:10.1088/0004-637X/791/2/121. Retrieved 8 December 2016. 
  6. ^ 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". The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407Freely accessible. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90. Retrieved 18 May 2016. 
  7. ^ a b Behrend, Raoul. "Asteroids and comets rotation curves – (1845) Helewalda". Geneva Observatory. Retrieved 18 May 2016. 
  8. ^ a b c Waszczak, Adam; Chang, Chan-Kao; Ofek, Eran O.; Laher, Russ; Masci, Frank; Levitan, David; et al. (September 2015). "Asteroid Light Curves from the Palomar Transient Factory Survey: Rotation Periods and Phase Functions from Sparse Photometry". The Astronomical Journal. 150 (3): 35. arXiv:1504.04041Freely accessible. Bibcode:2015AJ....150...75W. doi:10.1088/0004-6256/150/3/75. Retrieved 18 May 2016. 
  9. ^ a b Carbo, Landry; Green, Dawson; Kragh, Katherine; Krotz, Jonathan; Meiers, Andrew; Patino, Bernadette; et al. (October 2009). "Asteroid Lightcurve Analysis at the Oakley Southern Sky Observatory: 2008 October thru 2009 March". The Minor Planet Bulletin. 36 (4): 152–157. Bibcode:2009MPBu...36..152C. ISSN 1052-8091. Retrieved 18 May 2016. 
  10. ^ a b Brinsfield, James W. (October 2010). "Asteroid Lightcurve Analysis at the Via Capote Observatory: 2010 February-May". The Minor Planet Bulletin. 37 (4): 146–147. Bibcode:2010MPBu...37..146B. ISSN 1052-8091. Retrieved 18 May 2016. 
  11. ^ 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:1506.00762Freely accessible. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. Retrieved 18 May 2016. 
  12. ^ a b "1845 Helewalda (1972 UC)". Minor Planet Center. Retrieved 18 May 2016. 
  13. ^ Nesvorný, D.; Broz, M.; Carruba, V. (December 2014). "Identification and Dynamical Properties of Asteroid Families" (PDF). Asteroids IV: 297–321. arXiv:1502.01628Freely accessible. Bibcode:2015aste.book..297N. doi:10.2458/azu_uapress_9780816532131-ch016. Retrieved 21 November 2017. 
  14. ^ "Himmlischer Besuch auf der Sternwarte Eschenberg" (in German). Sternwarte Eschenberg. Retrieved 1 March 2016. Helen Gachnang and Susi Petit-Pierre visit the Eschenberg Observatory 
  15. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 18 May 2016. 

External links[edit]