The Gefion family (

FIN A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. F ...

: 516; adj. ''Gefionian''; also known as the Ceres family or the Minerva family) is an

asteroid family An asteroid family is a population of asteroids that share similar proper orbital elements, such as semimajor axis, eccentricity, and orbital inclination. The members of the families are thought to be fragments of past asteroid collisions. An ...

located in the intermediate

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids ...

between 2.74 and 2.82 AU at

inclinations Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

of 7.4° to 10.5 °. The family of

S-type asteroid S-type (stony-type or silicaceous-type) asteroids are asteroids with a spectral type that is indicative of a siliceous (i.e. stony) mineralogical composition, hence the name. They have relatively high density. Approximately 17% of asteroids are ...

s is named after 1272 Gefion and consists of more than 2,500 known members. It had previously been known as the Ceres family. It is still known as Minerva family, named after then thought parent body 93 Minerva, until it was identified to be an interloper into its own family.

Properties

The members have

proper orbital elements __NOTOC__ The proper orbital elements or proper elements of an orbit are constants of motion of an object in space that remain practically unchanged over an astronomically long timescale. The term is usually used to describe the three quantities ...

in the approximate ranges At the present

epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided b ...

, the range of osculating

orbital elements Orbital elements are the parameters required to uniquely identify a specific orbit. In celestial mechanics these elements are considered in two-body systems using a Kepler orbit. There are many different ways to mathematically describe the same o ...

of these core members is The namesake is

1272 Gefion 1272 Gefion, provisional designation , 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 Reinmu ...

. The family is fairly large, e.g. the Zappala 1995 analysis found about a hundred core members. A search of a recent proper element database found 766 objects (about 0.8% of the total) lying within the region defined by the first table above. 2631 Zhejiang has a diameter of 34 km, and is the largest core member whose diameter has been reliably estimated, although 2911 Miahelena is brighter, and would have a rough diameter of about 47 km, given the same (very low) albedo of 0.025.

Alternative name and interlopers

Until recently, this family was known as the Ceres family (adj. ''Cererean'') or the Minerva family (adj. ''Minervian'') after 1 Ceres (the largest asteroid) or 93 Minerva. However, spectroscopic analyses showed that these largest members were in fact interlopers in their own family, having a different

spectral class In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

from the bulk of the members. Other known interlopers are 255 Oppavia, 374 Burgundia, 2507 Bobone, and 2559 Svoboda.Identified by inspection of th
SMASSII data set
, S.J. Bus and R.P. Binzel, ''Phase II of the Small Main-Belt Asteroid Spectroscopic Survey'', Icarus Vol. 158, p. 106 (2002). This left the fairly minor asteroid 1272 Gefion as the lowest-numbered member.

List of members

This is a list of the known family members, without the above-mentioned interlopers.

References

{{DEFAULTSORT:Gefion Family * Asteroid groups and families