Minor Members of the Solar System

Dwarf PlanetsAccording 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.

CeresDiscovered on January 1, 1801Considered as a planet for half a

century before it was reclassified as an asteroid

Classified as a dwarf planet on September 13, 2006

PlutoDiscovered on February 18, 1930Classified as a planet for 76

yearsClassified as a dwarf planet on

August 24, 2006

MakemakeDiscovered on March 31, 2005Classified as a dwarf planet on

July 11, 2008

ErisDiscovered on January 5, 2005The media once referred to it as

the “tenth planet”Accepted as a dwarf planet on

September 13, 2006

HaumeaDiscovered on December 28,

2004Accepted as a dwarf planet on

September 17, 2008

Orbital Attributes of Dwarf Planets

Dwarf Planets

Region of Solar

System

Orbital Radius (AU)

Orbital Period (Earth years)

Mean Orbital Speed (km/s)

Ceres 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

Physical Properties of Dwarf PlanetsDwarf Planet

Equatorial Diameter

Relative Mass (w/ respect to Earth)

Density (g/cm3

)

Surface Gravity (m/s2)

Rotation Period (days)

Moons

Ceres 947.6 ±3.2

0.0002 2.08 0.27 0.38 0

Pluto 2306±30

0.0021 2..0 0.58 -6.39 3

Makemake 1500+400 −200

0.00067 ~2? ~0.5 - 0

Eris 2400±100

0.0025 2.3 ~0.8 ~0.3 1

Haumea 1150+250 −200

0.00067 2.6-3.3 ~0.44 - 2

PlutoSecond largest known dwarf planet in the

solar systemTenth largest body observed directly

orbiting the sunLargest member of a distinct region called

Kuiper Belt Composed of rock and iceRelatively small, approximately one-fifth

the mass of the Earth and one-third its volume

Highly eccentric and highly inclined orbitCharon is classified as its moonHas two known smaller moons, Nix and

Hydra

AsteroidsPieces 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

AsteroidsCeres, 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

AsteroidsOther asteroids are outside the orbit of

JupiterOver 2000 asteroids measuring 1 km in

diameter cross Earth’s orbit at timesAsteroid 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

AsteroidsSome 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