1272 Gefion

1272 Gefion, provisional designation 1931 TZ1, is a stony asteroid and parent body of the Gefion family from the central region of the asteroid belt, approximately 7 kilometers in diameter. It was discovered on 10 October 1931, by astronomer Karl Reinmuth at the Heidelberg Observatory in Germany. The asteroid was named after Gefjon from Norse mythology.[3]

1272 Gefion
Discovery [1]
Discovered byK. Reinmuth
Discovery siteHeidelberg Obs.
Discovery date10 October 1931
Designations
(1272) Gefion
Pronunciation/ˈɡeɪfiɒn/ or /ˈɡɛfiɒn/[2]
Named after
Gefjon [3]
(Norse mythology)
1931 TZ1 · A917 SF
main-belt · (middle)
Gefion [4]
AdjectivesGefionian /ɡɛfiˈoʊniən/[5]
Orbital characteristics [1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc99.50 yr (36,344 days)
Aphelion3.2076 AU
Perihelion2.3604 AU
2.7840 AU
Eccentricity0.1521
4.65 yr (1,697 days)
215.36°
0° 12m 43.92s / day
Inclination8.4185°
321.56°
3.6671°
Physical characteristics
Dimensions6.965±0.169 km[6]
7.016±0.066 km[7]
12.62 km (calculated)[8]
2.900±0.0012 h[9]
3.087±0.0005 h[9]
0.057 (assumed)[8]
0.2489±0.0256[7]
0.252±0.041[6]
SMASS = Sl [1]
C (assumed)[8]
12.785±0.005 (R)[9] · 12.9[7] · 13.0[1] · 13.01±0.21[10] · 13.22[8]

    Orbit and classification

    Gefion is the namesake and parent body of the Gefion family (516),[4] a large family of stony asteroids in the intermediate main belt.[11]:23 The family is also a suspected source of the L chondrites, common group of meteorites.[12]

    It orbits the Sun in the central main-belt at a distance of 2.4–3.2 AU once every 4 years and 8 months (1,697 days; semi-major axis of 2.78 AU). Its orbit has an eccentricity of 0.15 and an inclination of 8° with respect to the ecliptic.[1]

    The asteroid was first identified as A917 SF at Heidelberg in September 1917. The body's observation arc begins at Heidelberg, six days after its official discovery observation.[13]

    Physical characteristics

    In the SMASS classification, Gefion is a Sl-subtype that transitions from the common stony S-type asteroids to the rather rare L-types.[1]

    Rotation period

    In 2010 and 2011, two rotational lightcurves of Gefion were obtained from photometric observations in the R-band by astronomers at the Palomar Transient Factory in California . Lightcurve analysis gave a rotation period of 2.900 and 3.087 hours with a brightness amplitude of 0.22 and 0.20 magnitude, respectively (U=2/2).[9]

    Diameter and albedo

    According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Gefion measures between 6.965 and 7.016 kilometers in diameter and its surface has an albedo between 0.2489 and 0.252.[6][7] The Collaborative Asteroid Lightcurve Link assumes a standard albedo for carbonaceous asteroids of 0.057 and consequently calculates a much larger diameter of 12.62 kilometers based on an absolute magnitude of 13.22.[8]

    Naming

    This minor planet was named after Gefjon a goddess in Norse mythology. It is also named for the Gefion Fountain in Copenhagen, Denmark. The official naming citation was mentioned in The Names of the Minor Planets by Paul Herget in 1955 (H 117).[3]

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    References
    1. "JPL Small-Body Database Browser: 1272 Gefion (1931 TZ1)" (2017-03-29 last obs.). Jet Propulsion Laboratory. Retrieved 17 November 2017.
    2. Joseph Thomas (1915) Universal Pronouncing Dictionary of Biography and Mythology
    3. Schmadel, Lutz D. (2007). "(1272) Gefion". Dictionary of Minor Planet Names – (1272) Gefion. Springer Berlin Heidelberg. p. 105. doi:10.1007/978-3-540-29925-7_1273. ISBN 978-3-540-00238-3.
    4. "Asteroid 1272 Gefion – Nesvorny HCM Asteroid Families V3.0". Small Bodies Data Ferret. Retrieved 26 October 2019.
    5. Charles Dickens, ed. 1861. All the year round, 4:445.
    6. Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Dailey, J.; et al. (November 2011). "Main Belt Asteroids with WISE/NEOWISE. I. Preliminary Albedos and Diameters". The Astrophysical Journal. 741 (2): 20. arXiv:1109.4096. Bibcode:2011ApJ...741...68M. doi:10.1088/0004-637X/741/2/68. Retrieved 17 November 2017.
    7. 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:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90.
    8. "LCDB Data for (1272) Gefion". Asteroid Lightcurve Database (LCDB). Retrieved 17 November 2017.
    9. 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 17 November 2017.
    10. 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 17 November 2017.
    11. Nesvorný, D.; Broz, M.; Carruba, V. (December 2014). Identification and Dynamical Properties of Asteroid Families. Asteroids IV. pp. 297–321. arXiv:1502.01628. Bibcode:2015aste.book..297N. doi:10.2458/azu_uapress_9780816532131-ch016. ISBN 9780816532131.
    12. Nesvorný, David; Vokrouhlický, David; Morbidelli, Alessandro; Bottke, William F. (April 2009). "Asteroidal source of L chondrite meteorites" (PDF). Icarus. 200 (2): 698–701. Bibcode:2009Icar..200..698N. doi:10.1016/j.icarus.2008.12.016. Retrieved 17 November 2017.
    13. "1272 Gefion (1931 TZ1)". Minor Planet Center. Retrieved 17 November 2017.

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