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Asteroid Classification
Asteroids are commonly classified into groups
based on the characteristics of their orbits and
on the details of the spectrum of sunlight they
reflect.
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Orbit
Groups And Families
Asteroids
are divided into groups and families based on
their orbital characteristics. It is customary
to name a group of asteroids after the first member
of that group to be discovered. Groups are relatively
loose dynamical associations, whereas families
are much "tighter" and result from the
catastrophic break-up of a large parent asteroid
sometime in the past.
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Spectral
Classification
In
1975, an asteroid taxonomic system based on colour,
albedo, and spectral shape was developed by Clark R.
Chapman, David Morrison, and Ben Zellner.
These properties are thought to correspond to the composition
of the asteroid's surface material. Originally, they
classified only three types of asteroids:
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X
C-type asteroids - carbonaceous, 75% of known
asteroids
X
S-type asteroids - silicaceous, 17% of known asteroids
X
M-type asteroids - metallic, most of the remaining
asteroids
This list has since been expanded to include a
number of other asteroid types. The number of
types continues to grow as more asteroids are
studied. See List of asteroid types for a complete
list. Note that the proportion of known asteroids
falling into the various spectral types does not
necessarily reflect the proportion of all asteroids
that are of that type; some types are easier to
detect than others, biasing the totals.
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Problems
With Spectral Classification
Originally, spectral designations were based on
inferences of an asteroid's composition:
X
C - Carbonaceous
X
S - Silicaceous
X
M - Metallic
This has led to great confusion though in that
an asteroid's type is not indicative of its composition.
While asteroids of different spectral classifications
are likely to be composed of different materials,
there are no assurances that asteroids within
the same taxonomic class are composed of similar
materials.
Also see
vAsteroids
In Solar System
vAsteroids
Discovery
vAsteroids
Exploration
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