Dwarf Planets

Solar System Debris

Planets vs Dwarf PlanetsPlanets

– Orbits the Sun directly– Massive enough to be

rounded by its own gravity– Has cleared the smaller

bodies from its orbit

Dwarf Planets– Orbits the Sun directly– Massive enough to be

rounded by its own gravity– Has not cleared the smaller

bodies from its orbit

Official Dwarf Planets

1. Ceres – discovered on January 1, 1801 (45 years before Neptune),

2. Pluto – discovered on February 18, 1930,.

3. Eris – discovered on January 5, 2005.

4. Haumea – discovered on December 28, 2004. Makemake – discovered on March 31, 2005.

5.

The Dwarf Planets in Comparison

Name

Diameter relative to

Luna

Mass relative to

LunaDensity (Kg/m3)

Temperature (K)

Orbital period (yrs)

Ceres 28% 1.3% 2080 167 4.6

Pluto 69% 17.8% 2000 44 248

Haumea 33% 5.7% 2600-3300 32 285

Makemake 43% ~5%? ~2000? ~30 309

Eris 78% 22.7% 2300 42 557

Ceres• Found in the asteroid belt in 1801

• Considered a planet for half a century before reclassification as an asteroid.

• Once considered the largest asteroid

• Classified as a dwarf planet on September 13, 2006.

Ceres - The numbers– Contains 1/3 the total mass of all the asteroids– Orbital Period: 4.6 years– Semi-major axis: 2.8 AU– Diameter: 950 Km– Temperature: 167 K

Ceres – Discovery• Possibility of its existence first suggested in

1772• Discovered in 1801 by Giuseppe Piazzi• Named for the Roman goddess

of plants

Ceres - Characteristics • Surface like a C-class asteroid• Possibly differentiated interior?• Bright spot of unknown composition• Possible tenuous atmosphere and frost

The Dawn Mission

• Will study asteroids Vesta and Ceres

• Will arrive at Vesta in July 2011

• Will arrive at Ceres in February 2015

Kuiper Belt Objects (KBO)• AKA: Trans-Neptunian Objects (TNO)• Comet-like material• Disk beyond Neptune

Pluto• Considered the 9th planet from 1930 to 2006

• Classified as a planet for 76 years.

• Named for Roman god of the underworld

• Reclassified as a dwarf planet on August 24, 2006

• Became the first dwarf planet

Pluto - Discovery• Observations of Neptune

showed that something was perturbing its orbit

• In 1906 the Lowell Observatory began a search for “Planet X”

• Clyde Tombaugh discovered Pluto in 1930 using a blink comparator

Pluto - Discovery

Pluto in the blink comparator

Pluto - The numbers– Orbital Period: 248 years– Semi-major axis: 39 AU– Diameter: 2300 Km– Temperature: 44 K– 3 known moons• Charon : more than ½ the size of Pluto• Nix• Hydra

Pluto – The Orbit

• Highly eccentric– Inside Neptune from 79-99

• Tilted 17º from ecliptic

Pluto – What is it really?

• Highly eccentric orbit• +Atmosphere thaws and freezes depending on

distance from Sun• +Highly inclined from ecliptic• = comet

Haumea

• A plutoid– Dwarf planets beyond

Neptune

• Named after the goddess of the island of Hawaii

• Has two known moons

Haumea - Discovery

• Discovered in 2004 by Mike Brown at CalTech

• Discovery first announced by a Spanish team …BUT!

• They stole the data• Accepted as a dwarf planet

on September 17, 2008.

Haumea’s Shape• Spins very fast– A rotation in 4 hours

• This rotation causes it to deform

• Formed into football shape

Haumea – the numbers

– Orbital Period: 285 years– Diameter: ~1400Km– Semi-major axis: 43.1 AU– Temperature: <50 K

Makemake

• Plutoid• Named for the

creator god of Easter Island

• No known satellites– Unique among large

KBOs

Makemake - Discovery

• Discovered in 2005 by Mike Brown at CalTech

• Further from ecliptic than other dwarfs

• Accepted as a dwarf planet on July 11, 2008.

Makemake – the nubmers

– Orbital Period: 309 years

– Semi-major axis: 43.1 AU

– Inclination: 29º– Diameter: 1500Km– Temperature: 30-35 K

Eris• Largest dwarf planet in

solar system• 27% more massive than

Pluto• Named for Greek goddess

of discord

Eris - Discovery

• Discovered in 2005 by Mike Brown at CalTech

• Called the "tenth planet” in media reports

• Originally named Xena

• Accepted as a dwarf planet on September 13, 2006.

Eris? Really?

Me again.

Eris – The numbers

– Orbital Period: 557 years– Semi-major axis: 68 AU– Diameter: 2400? Km– Temperature: 42.5 K– 1 known moon• Dysnomia

Other Trans-Neptunian Objects

Pluto’s Demise