Because there are so many asteroids, they are classified into groups with similar characteristics. The defining characteristics are
q - the closest the asteroid gets to the Sun (perihelion).
a - the farthest the asteroid gets from the Sun (aphelion)
The orbital period sometimes has a relationship (resonance) with a planet.
The following is not an exhaustive list of groups and sub groups (values of a and p are given in Astronomical Units - i.e. the mean distance of the Earth from the Sun)
Amor q> 1.017 and q<1.017
Apollo q<1.017 but a>1
Aten a<1
Damocloids named after Asteroid 5335 Damocles, these objects are in orbits similar to short-period comets (like Halley's Comet). They could be old comets that have shed their gaseous envelope and now resemble an asteroid, rather than a true minor planet.
In 1998 Jiri Borovicka reported to the IAU Colloquium in Tatranska Lomnica of a fireball he detected in 1997. This had a retrograde cometary orbit which suggests it was a Damocloid.
It is interesting that the meteorite was quite compact and that its velocity was 65km/s.
CCNet 97/2001 4 September 2001
Hungaria asteroids orbit in the inner portion of the main asteroid belt, at a distance of about 1.9 AU. They have high inclinations, ranging from 20 to 30 degrees and low eccentricity (man value around 0.05) Some people think the Hungaria asteroids may be an early stage for Near-Earth asteroids.
Flora a > 2.1 and a < 2.3 Inclination 11 degrees
Main Belt Asteroids p >Mars a <Jupiter
Cybeles a >3.31 and a< 3.57 (approx) 4:7 resonance with Jupiter
Hildas a > 3.9 and a <4.1 2:3 reonance with Jupiter
Thule so far only one object in this class (namely Thule itself) It has a resonance of 3:4 with Jupiter. There is a gap in the asteroid belt juts after Thule.
Trojans a> 5 and a <5.4
Centaurs a >5.4 and a < 30 (approx) The definition of this group is not absolute.
Trans Neptune Objects a>30
Plutinos (like Pluto) 3:2 resonance with Neptune a>39 and a <41
Cubewanos (like 1992 QB1) a> 41 and a < 47 (approx)
1997 SZ 10 (one object in this class) has a resonance of 2:1 with Neptune.
Surface temperature could be as high as 1300 Kelvin when closest to the Sun!
1995 CR
0.12
3200 Phaethon
0.14
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