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3309 Brorfelde, provisional designation 1982 BH, is a nearly spheroidal, binary[a] Hungaria asteroid from the inner regions of the asteroid belt, approximately 4 kilometers in diameter. It was discovered on 28 January 1982, by Danish astronomers Kaare Jensen and Karl Augustesen at the Brorfelde Observatory near Holbæk, Denmark.[3] It was named for the discovering observatory and the village where it is located.[2]

3309 Brorfelde
Discovery [1]
Discovered byK. Jensen
K. Augustesen
Discovery siteBrorfelde Obs.
Discovery date28 January 1982
MPC designation(3309) Brorfelde
Named after
Brorfelde Observatory
(discovering observatory)[2]
1982 BH
main-belt · Hungaria[3][4]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc35.25 yr (12,876 days)
Aphelion1.9143 AU
Perihelion1.7208 AU
1.8175 AU
2.45 yr (895 days)
0° 24m 7.92s / day
Known satellites1 [5][a]
Physical characteristics
Dimensions3.78±0.60 km[6]
3.91 km (derived)[4]
5.038±0.083 km[7]
2.503±0.001 h[8]
2.5041±0.0002 h[5][9]
2.5042±0.0001 h[10]
2.5046±0.0003 h[11]
6±2 h[12]
8±1 h[13]
9.3788±0.0022 h[14]
0.2747 (derived)[4]
SMASS = S[1] · S[4]
13.4±0.2 (R)[5] · 13.584±0.001 (R)[14] · 13.60[6][7] · 13.7[1] · 13.9[9] · 13.97±0.09[12] · 14.062±0.064[4][15]


Orbit and classificationEdit

Brorfelde is a bright stony asteroid and member of the Hungaria family, which form the innermost dense concentration of asteroids in the Solar System. It orbits the Sun at a distance of 1.7–1.9 AU once every 2 years and 5 months (895 days). Its orbit has an eccentricity of 0.05 and an inclination of 21° with respect to the ecliptic.[1] The body's observation arc begins with its official discovery observation, as no precoveries were taken, and no prior identifications were made.[3]

Physical characteristicsEdit

On the SMASS taxonomic scheme, Brorfelde is a common stony S-type asteroid.[1]


Between 2005 and 2010, astronomers Brian Warner and Petr Pravec obtained a large number of rotational lightcurves of Brorfelde. Best rated lightcurve analysis gave a rotation period between 2.5041 and 2.5046 hours with a brightness amplitude between 0.09 and 0.13 in magnitude, indicating that the body has a nearly spheroidal shape (U=3/3/3).[9][10]

These results superseded photometric observations taken by Wiesław Z. Wiśniewski in the 1990s (U=2),[12] and by Federico Manzini and René Roy in 2005 and 2009, respectively (U=2-/n.a.),[13] as well as observations taken at the Palomar Transient Factory in 2010, which gave an incorrect period solution of more than 9 hours (U=1).[14]


During the photometric observation in 2005, it was revealed that Brorfelde is a binary asteroid. Its asteroid moon has an orbital period of 18.48±0.01 hours, and measures approximately 1 kilometer in diameter, based on a mean-diameter ratio of 0.26±0.02 for the system's secondary and primary body.[a][5] In January 2014, repeated observations by Brian Warner confirmed a period of 2.503 and 18.51 hours for the primary and secondary, respectively (U=3),[8] with several online-published lightcurve plots.[b]

Diameter and albedoEdit

According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Brorfelde measures 3.78 kilometers in diameter, and its surface has an albedo of 0.46 (most recent result only).[6] The Collaborative Asteroid Lightcurve Link derives an albedo of 0.2747 and a diameter of 3.91 kilometers with an absolute magnitude of 14.062.[4]


This minor planet was named on the occasion of the Brorfelde Observatory's 40th anniversary. Brorfelde was the observatory's first minor planet discovery.[2] The approved naming citation was published by the Minor Planet Center on 7 September 1987 (M.P.C. 12210).[16]


  1. ^ a b c Electronic Telegram No. 279, (3309) Brorfelde, 7 November 2005[5]
    Photometric observations obtained from 25 October to 3 November 2005, revealed that 3309 Brorfelde is a binary system with an orbital period of 18.48±0.01 hours. The primary rotates with a period of 2.5041±0.0002 hours, and its light-curve has a brightness variation of 0.13 magnitude, indicating a nearly spheroidal shape. Mutual eclipse/occultation events with an amplitude of 0.07-0.15 magnitude suggest a ratio of 0.26±0.02 for its secondary-to-primary mean-diameter. Assuming G = 0.15, the calibrated data gives an absolute magnitude of 13.4±0.2.
    B. D. Warner, Palmer Divide Observatory, Colorado Springs; P. Pravec and P. Kusnirak, Ondrejov Observatory; W. Cooney, J. Gross, and D. Terrell, Sonoita Research Observatory, Sonoita, AZ; and S. Nudds, Elginfield Observatory, University of Western Ontario Central Bureau for Astronomical Telegrams No.279
  2. ^ Lightcure plots of (3309) Brorfelde at the Center for Solar System Studies (CS3) in 2014


  1. ^ a b c d e f "JPL Small-Body Database Browser: 3309 Brorfelde (1982 BH)" (2017-05-02 last obs.). Jet Propulsion Laboratory. Retrieved 3 July 2017.
  2. ^ a b c Schmadel, Lutz D. (2007). "(3309) Brorfelde". Dictionary of Minor Planet Names – (3309) Brorfelde. Springer Berlin Heidelberg. p. 276. doi:10.1007/978-3-540-29925-7_3310. ISBN 978-3-540-00238-3.
  3. ^ a b c "3309 Brorfelde (1982 BH)". Minor Planet Center. Retrieved 9 January 2017.
  4. ^ a b c d e f "LCDB Data for (3309) Brorfelde". Asteroid Lightcurve Database (LCDB). Retrieved 9 January 2017.
  5. ^ a b c d e Warner, B. D.; Pravec, P.; Kusnirak, P.; Cooney, W.; Gross, J.; Terrell, D.; et al. (November 2005). "(3309) Brorfelde". Central Bureau Electronic Telegrams. 279 (279): 1. Bibcode:2005CBET..279....1W. Retrieved 9 January 2017.
  6. ^ a b c d Nugent, C. R.; Mainzer, A.; Masiero, J.; Bauer, J.; Cutri, R. M.; Grav, T.; et al. (December 2015). "NEOWISE Reactivation Mission Year One: Preliminary Asteroid Diameters and Albedos". The Astrophysical Journal. 814 (2): 13. arXiv:1509.02522. Bibcode:2015ApJ...814..117N. doi:10.1088/0004-637X/814/2/117. Retrieved 9 January 2017.
  7. ^ a b c d Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Nugent, C.; et al. (November 2012). "Preliminary Analysis of WISE/NEOWISE 3-Band Cryogenic and Post-cryogenic Observations of Main Belt Asteroids". The Astrophysical Journal Letters. 759 (1): 5. arXiv:1209.5794. Bibcode:2012ApJ...759L...8M. doi:10.1088/2041-8205/759/1/L8. Retrieved 9 January 2017.
  8. ^ a b Warner, Brian D. (July 2014). "Asteroid Lightcurve Analysis at CS3-Palmer Divide Station: 2014 January-March". The Minor Planet Bulletin. 41 (3): 144–155. Bibcode:2014MPBu...41..144W. ISSN 1052-8091. Retrieved 9 January 2017.
  9. ^ a b c Warner, Brian D.; Pravec, Petr; Kusnirak, Peter; Harris, Alan W.; Cooney, Walter R., Jr.; Gross, John; et al. (April 2011). "Lightcurves from the Initial Discovery of Four Hungaria Binary Asteroids". The Minor Planet Bulletin. 38 (2): 107–109. Bibcode:2011MPBu...38..107W. ISSN 1052-8091. Retrieved 9 January 2017.
  10. ^ a b Pravec, P.; Scheirich, P.; Vokrouhlický, D.; Harris, A. W.; Kusnirák, P.; Hornoch, K.; et al. (March 2012). "Binary asteroid population. 2. Anisotropic distribution of orbit poles of small, inner main-belt binaries". Icarus. 218 (1): 125–143. Bibcode:2012Icar..218..125P. doi:10.1016/j.icarus.2011.11.026. Retrieved 9 January 2017.
  11. ^ Warner, Brian D. (July 2009). "Analysis of the Hungaria Binary Asteroid 3309 Brorfelde". The Minor Planet Bulletin. 36 (3): 108. Bibcode:2009MPBu...36..108W. ISSN 1052-8091. Retrieved 9 January 2017.
  12. ^ a b c Wisniewski, W. Z.; Michalowski, T. M.; Harris, A. W.; McMillan, R. S. (March 1995). "Photoelectric Observations of 125 Asteroids". Abstracts of the Lunar and Planetary Science Conference. 26: 1511. Bibcode:1995LPI....26.1511W. Retrieved 9 January 2017.
  13. ^ a b Behrend, Raoul. "Asteroids and comets rotation curves – (3309) Brorfelde". Geneva Observatory. Retrieved 9 January 2017.
  14. ^ 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:1504.04041. Bibcode:2015AJ....150...75W. doi:10.1088/0004-6256/150/3/75. Retrieved 9 January 2017.
  15. ^ Pravec, Petr; Harris, Alan W.; Kusnirák, Peter; Galád, Adrián; Hornoch, Kamil (September 2012). "Absolute magnitudes of asteroids and a revision of asteroid albedo estimates from WISE thermal observations". Icarus. 221 (1): 365–387. Bibcode:2012Icar..221..365P. doi:10.1016/j.icarus.2012.07.026. Retrieved 9 January 2017.
  16. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 9 January 2017.

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