THE SOLAR SYSTEM
Asteroid 243 Ida with
its satellite, Dactyl, imaged on
28 August 1993 by the Galileo
spacecraft. Ida is a member of
the Koronis group of
asteroids, moving around the
Sun at a mean distance of 430
million km (267 million miles)
in a period of 4.84 years. Itmeasures 56 24 21 km (35
15 13 miles); Dactyl has a
diameter of about
1 km (0.6 mile). The separation
is about 100 km (60 miles).
Both bodies were probably
formed at the same time when
a larger object broke up
during a collision.SOME MAIN-BELT ASTEROIDS ASTEROID TYPES
DesignationType Example
C Carbonaceous; spectra resemble carbonaceous 1 Ceres
chondrites
S Silicaceous; generally reddish; spectra resemble 5 Astraea
chondrites
M Metallic; perhaps metal-rich cores of former larger 16 Psyche
bodies which have been broken up by collision
E Enstatite; rare, resemble some forms of chondrites 434 Hungaria
in which enstatite (MgSiO 3 ) is a major constituent
D Reddish; surface rich in clays 336 Lacadiera
A Almost pure olivine 446 Aeternitas
PPeculiar spectra; not too unlike type M 87 Sylvia
Q Close-approach asteroids; resemble chondrites 4581 Asclepius
V Igneous rock surfaces; Vesta is the only large 4 Vesta
example
U Unclassifiable 72 FeroniaName Distance from Sun, Period, Type Diameter, Mag. Rotation
astronomical units years km period
min. max. max. hour
1 Ceres 2.55 2.77 4.60 C 940 7.4 9.08
2 Pallas 2.12 2.77 4.62 CU 580 8.0 7.81
3 Juno 1.98 2.87 4.36 S 288 8.7 7.21
4 Vesta 2.15 2.37 3.63 V 576 6.5 5.34
5 Astraea 2.08 2.57 4.13 S 120 9.8 16.81
10 Hygeia 2.76 3.13 5.54 C 430 10.2 17.50
16 Psyche 2.53 2.92 5.00 M 248 9.9 4.20
44 Nysa 2.06 2.42 3.77 S 84 10.2 5.75
72 Feronia 1.99 2.67 3.41 U 96 12.0 8.1
132 Aethra 1.61 2.61 4.22 SU 38 11.9?
253 Mathilde 1.94 3.35 5.63 C 66 48 46 10.0?
279 Thule 4.22 4.27 8.23 D 130 15.4?
288 Glauke 2.18 2.76 4.58 S 30 13.2 1500
704 Interamnia 2.61 3.06 5.36 E 338 11.0 8.7
243 Ida 2.73 2.86 4.84 S 52 14.6 5.0 Preliminary map of Vesta,
from the Hubble Space
Telescope in 1994 (blue
light). The dark circular
feature (Olbers) may be
a 200-km (125-mile) crater.
The lower panel is a
false-colour composite of
visible and near-infra-red
images, indicating that
different minerals dominate
the hemisphere of Vesta
on the left and right. Vesta, from the Hubble
Space Telescope, in
November–December 1994.
The images in each row
were taken in red light,
9 minutes apart; the axial
spin is clearly demonstrated.C Atl of Univ Phil'03stp 2/4/03 3:07 pm Page 91