Gefion family

Lore & Background

The Gefion family is an S-type asteroid family located in the intermediate belt. Its members have proper orbital elements in approximate ranges of 2.74 to 2.82 AU and inclinations of 7.4° to 10.5°. The family was originally known as the Ceres family, after 1 Ceres, the largest asteroid, and later as the Minerva family, after 93 Minerva, which was thought to be the parent body. However, spectroscopic analyses showed that both Ceres and Minerva are interlopers, belonging to a different spectral class than the bulk of the family. This left the relatively minor asteroid 1272 Gefion as the lowest-numbered member and the namesake.

The family is fairly large; the Zappala 1995 analysis found about a hundred core members. A search of a recent proper element database identified 766 objects (about 0.8% of the total) lying within the defined region. Among the core members, 2631 Zhejiang has a reliably estimated diameter of 34 km, while 2911 Miahelena is brighter and would have a rough diameter of about 47 km, assuming the same very low albedo of 0.025.

Known interlopers include 255 Oppavia, 374 Burgundia, 2507 Bobone, and 2559 Svoboda, in addition to Ceres and Minerva. The family is also designated FIN: 516.

Reader's Guide

The Gefion family's significance lies in its role as a cautionary example in asteroid taxonomy, where the largest members of a family were found to be unrelated interlopers. This discovery reshaped understanding of asteroid family formation and identification, demonstrating that spectroscopic analysis is essential for confirming parent bodies. The family's history—from being called the Ceres family to the Minerva family, and finally the Gefion family—illustrates the evolving nature of asteroid classification. With more than 2,500 known members, it is a substantial group in the intermediate belt, yet its core members are relatively small, with the largest reliably measured being 2631 Zhejiang at 34 km. The presence of interlopers such as 1 Ceres and 93 Minerva, which are much larger and spectrally distinct, highlights the complexity of asteroid families and the need for careful analysis. The family's legacy includes its use as a reference for studying collisional evolution and the dynamics of the asteroid belt, as well as the ongoing refinement of family membership through proper element databases.

Did You Know?

• The Gefion family was previously known as the Ceres family and the Minerva family.
• 1 Ceres and 93 Minerva were found to be interlopers in their own family due to different spectral classes.
• The family contains more than 2,500 known members.
• 2631 Zhejiang is the largest core member with a reliably estimated diameter of 34 km.