Gefion-asteroid

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Lokalisering och struktur av Gefion-familjen.

Gefion-asteroiderna, eller Gefion-familjen, även känd som Ceres-asteroiderna, eller Minerva-familjen är en grupp asteroider i de centrala delarna av asteroidbältet. Den är en av de största asteroidfamiljerna, den har fler än 2 500 kända medlemmar.

Gemensamt för asteroider i gruppen är att de har en omloppsbana runt solen med en halv storaxel på mellan 2,74 och 2,82 AU och en excentricitet mellan 0,081 och 0,180 AU.

Familjen har fått namn efter medlemmen 1272 Gefion.

Referenser

Den här artikeln är helt eller delvis baserad på material från engelskspråkiga Wikipedia, Gefion family, 27 september 2021.

Media som används på denna webbplats

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Författare/Upphovsman: Tkgd2007, Licens: CC BY-SA 3.0
A new incarnation of Image:Question_book-3.svg, which was uploaded by user AzaToth. This file is available on the English version of Wikipedia under the filename en:Image:Question book-new.svg
Gefion family.png
(c) Deuar, CC-BY-SA-3.0

Diagrams showing the location and characteristics of the en:Gefion family of en:asteroids. Where circles are plotted, their diameter is proportional to the mean diameter of the asteroid.

In the top diagrams, the en:proper orbital elements are plotted (en:inclination ip vs. en:semi-major axis ap on the left, and en:inclination ip vs. eccentricity ep on the right) for numbered en:asteroids in the en:main belt.

In the bottom enlargements, one has:

  • core family members (shown in red) are those identified by the 1995 Zappala (V. Zappala et al., Icarus Vol. 116, p. 291 (1995)) HCM method analysis (as the Ceres family). The data set is here.
  • outer family members (shown in purple) were identified by the same analysis, but are somewhat less certain to be members (were given a quality tag of "1" in the data-set)
  • interlopers (shown in green) were identified either:
    • in A. Cellino et al. "Spectroscopic Properties of Asteroid Families", in Asteroids III, p. 633-643, University of Arizona Press (2002) (table on page 636, in particular),
    • and also by inspection of the PDS asteroid taxonomy data set for non S-type members of the above Zappala 1995 data.
  • additional significant asteroids (shown in light blue) in the vicinity. (en:93 Minerva is not a en:Gefion family member)
  • numbered asteroids in general (shown as small blue dots), from the AstDys database.

The location of asteroids that are very large and/or explicitly named on the plot is shown by a light cross within the circle.

Asteroid diameters were obtained from two sources:

  • (thick circles): From the IRAS survey, when available (data set here).
  • (thin circles): Otherwise, by assuming an albedo of 0.1 (approximate average of non-interlopers in the IRAS survey), and estimating from absolute magnitudes from the AstOrb database here.

The diagrams were created by me (Piotr Deuar) using proper element data for 96944 en:minor planets, which was obtained from the AstDys site. Data was dated March 2005, calculation was by Z. Knezevic and A. Milani.

The top left plot is a slightly modified reduced version of en:Image:Asteroid_proper_elements_i_vs_a.png.