Download Minor Members of the Solar System

Dwarf Planets
According to IAU (International Astronomical
Union), a "dwarf planet" is a celestial body
that
1) is in orbit around the Sun,
2) has sufficient mass for its self-gravity to
assume a nearly round shape,
3) has not cleared the neighborhood around
its orbit, and
4)is not a satellite.
A dwarf planet has been referred to by
some astronomers as “something that
looks like a planet, but is not a planet.”
 There are five known dwarf planets –
Ceres, Pluto, Makemake, Eris and Haumea.
 Dwarf planets may also be called minor
planets, subplanets or planetoids.

Ceres
Discovered on January 1, 1801
 Considered as a planet for half a century
before it was reclassified as an asteroid
 Classified as a dwarf planet on September
13, 2006

Pluto
Discovered on February 18, 1930
 Classified as a planet for 76 years
 Classified as a dwarf planet on August 24,
2006

Makemake
Discovered on March 31, 2005
 Classified as a dwarf planet on July 11,
2008

Eris
Discovered on January 5, 2005
 The media once referred to it as the
“tenth planet”
 Accepted as a dwarf planet on September
13, 2006

Haumea
Discovered on December 28, 2004
 Accepted as a dwarf planet on September
17, 2008

Orbital Attributes of Dwarf Planets
Orbital
Radius (AU)
Orbital
Period
(Earth
years)
Mean
Orbital
Speed
(km/s)
Asteroid
belt
2.77
4.60
17.882
Pluto
Kuiper
belt
39.48
248.09
4.666
Makemake
Kuiper
belt
45.79
309.9
4.419
Eris
Scattered
disc
67.67
557
3.436
Haumea
Kuiper
belt
43.34
285.4
4.484
Dwarf
Planets
Region of
Solar
System
Ceres
Physical Properties of Dwarf Planets
Dwarf Planet
Equatori
al
Diamete
r
Relative
Mass (w/
Ceres
947.6
±3.2
Pluto
Density
(g/cm3)
Surface
Gravity
(m/s2)
Rotation
Period
(days)
Moons
0.0002
2.08
0.27
0.38
0
2306±30
0.0021
2..0
0.58
-6.39
3
Makemake
1500+400
0.00067
~2?
~0.5
-
0
Eris
2400±100 0.0025
2.3
~0.8
~0.3
1
Haumea
1150+250
2.6-3.3
~0.44
-
2
−200
−200
respect to
Earth)
0.00067
Pluto
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Second largest known dwarf planet in the solar
system
Tenth largest body observed directly orbiting the sun
Largest member of a distinct region called Kuiper
Belt
Composed of rock and ice
Relatively small, approximately one-fifth the mass of
the Earth and one-third its volume
Highly eccentric and highly inclined orbit
Charon is classified as its moon
Has two known smaller moons, Nix and Hydra
Asteroids
Pieces of irregularly shaped, solid bodies
or rocks orbiting around the sun
 All are moving counterclockwise around
the sun, just as planets do
 Vesta is the brightest asteroid but it
cannot be seen by the naked eye
 In the asteroid belt, they range in size
from tiny particles to about 1000 km in
diameter

Asteroids
Ceres, the largest asteroid and first one
to be discovered has a diameter of about
940 km
 Some asteroids have orbits that cross the
orbit of Mars
 Trojan asteroids follow the same orbit as
Jupiter
 One group of Trojan asteroids travels
ahead of Jupiter, while the other group
trails behind

Asteroids
Other asteroids are outside the orbit of
Jupiter
 Over 2000 asteroids measuring 1 km in
diameter cross Earth’s orbit at times
 Asteroid belt is an area between the
orbits of Mars and Jupiter where most
asteroids exist
 Asteroid belt may have been formed
when a planet was pulled apart into
fragments by gravitational force of Jupiter

Asteroids
Some larger asteroids may have been
ejected from the asteroid belt and are
currently scattered in the solar system
 Several asteroids have been named after
Filipino scientists and educators, Kintanar,
Edwelda, Badillo, Biyo and students who
won in the Science and Engineering Fair,
Estrella, Rara, and Macalintal
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