THE DWARF PLANETSTHE DWARF PLANETS

What makes a PLANET?What makes a PLANET?

Planets must:Planets must: Be in orbit around Sun.Be in orbit around Sun. Have enough mass so gravity makes them round.Have enough mass so gravity makes them round. Have cleared their orbit of similar objects.Have cleared their orbit of similar objects.

Dwarf PlanetsDwarf Planets

According to the According to the International Astrnomical International Astrnomical Union (IAU)Union (IAU), , these are types of celestial these are types of celestial bodies in the solar system that has a bodies in the solar system that has a

rounded shape rounded shape like a major planet, but like a major planet, but

is is too small to clear other bodiestoo small to clear other bodies from the region of space around its orbit from the region of space around its orbit

with its own gravity.with its own gravity.

Dwarf PlanetsDwarf Planets

They have sufficient mass to overcome They have sufficient mass to overcome rigid body forces and achieve rigid body forces and achieve hydrostatic equilibriumhydrostatic equilibrium*.*.

Hydrostatic equilibrium Hydrostatic equilibrium happens when the happens when the pull of gravity is balanced by a pressure pull of gravity is balanced by a pressure gradient which creates a pressure-gradient gradient which creates a pressure-gradient force in the other direction.force in the other direction.

Dwarf PlanetsDwarf Planets

They They orbit the Sunorbit the Sun, and may have moons , and may have moons and atmospheres like planets.and atmospheres like planets.

Usually are found in regions of the solar Usually are found in regions of the solar system that contain swarms of other system that contain swarms of other small bodies: the small bodies: the asteroid beltasteroid belt, the , the Kuiper BeltKuiper Belt, and the , and the Oort CloudOort Cloud..

They should not be confused with minor They should not be confused with minor planets.planets.

Dwarf PlanetsDwarf Planets

Adopted in Adopted in 20062006 as part of a three-way as part of a three-way categorization of bodies orbiting the sun, categorization of bodies orbiting the sun, brought about by the increase in dis-brought about by the increase in dis-coveries of coveries of Trans-Neptunian Objects*Trans-Neptunian Objects* ..

A A Trans-NeptunianTrans-Neptunian Object Object is any object in the Solar is any object in the Solar System that orbits the Sun at a greater average distance System that orbits the Sun at a greater average distance than Neptune. The first trans-Neptunian object to be than Neptune. The first trans-Neptunian object to be discovered was the dwarf planet Pluto in 1930.discovered was the dwarf planet Pluto in 1930.

Trans-Neptunian ObjectsTrans-Neptunian Objects

Dwarf PlanetsDwarf Planets

Currently recognized dwarf planets Currently recognized dwarf planets include include PlutoPluto (formerly counted as the (formerly counted as the ninth planet), ninth planet), ErisEris, , MakemakeMakemake,, HaumeaHaumea and and CeresCeres (formerly (formerly considered the largest asteroid).considered the largest asteroid).

Only Ceres and Pluto have been Only Ceres and Pluto have been observed in enough detail and proven observed in enough detail and proven to fit the definition of a dwarf planet.to fit the definition of a dwarf planet.

THE FIVE DWARF THE FIVE DWARF PLANETSPLANETS

ERISERIS Largest known Largest known

dwarf planet.dwarf planet. Approximately Approximately 2, 2,

500 km 500 km in in diameterdiameter

27 %27 % more more massive than massive than Pluto.Pluto.

ERISERIS Current distance Current distance

from the sun is from the sun is 96.7 96.7 AU.AU.

Orbits Orbits 3 times 3 times more more distant than Pluto.distant than Pluto.

557 years557 years to make to make one revolution one revolution around the Sun.around the Sun.

ERISERIS Has one moon, Has one moon,

Dysnomia.Dysnomia. Surface might Surface might

be covered be covered with with frozen methane.frozen methane.

First spotted in First spotted in 20052005

PLUTOPLUTO PlutoPluto was the Roman name was the Roman name

for Hades, the for Hades, the Greek god of Greek god of the Underworldthe Underworld..

Discovered in Discovered in 19301930 by by Clyde Clyde TombaughTombaugh using a blink using a blink comparator. This allowed comparator. This allowed astronomers to quickly look astronomers to quickly look for differences in two for differences in two photographs shot on different photographs shot on different nights of the same part of the nights of the same part of the sky.sky.

SecondSecond largest dwarf largest dwarf planet and planet and tenthtenth largest largest body observed directly body observed directly orbiting the sun.orbiting the sun.

Once thought of as Once thought of as usually the usually the furthest furthest planetplanet from the sun. from the sun.

2/32/3 the size of our the size of our moon.moon.

Has one large moon, Has one large moon, CharonCharon, and two smaller , and two smaller ones, ones, NixNix and and HydraHydra..

PLUTOPLUTO

So cold that So cold that oxygenoxygen and and nitrogennitrogen in its in its atmosphere is atmosphere is frozen frozen solidsolid except when except when Pluto is nearer the Sun.Pluto is nearer the Sun.

Only planet not visitedOnly planet not visited by a spacecraft.by a spacecraft.

Pluto takes Pluto takes 248 years 248 years to make one orbit to make one orbit around the sun!around the sun!

PLUTOPLUTO

ThirdThird largest dwarf largest dwarf planet, after Eris and planet, after Eris and Pluto.Pluto.

One of the two largest One of the two largest Kuiper Belt Objects (KBO)Kuiper Belt Objects (KBO)

Diameter is Diameter is ¾¾ that of that of Pluto.Pluto.

No known moons or No known moons or satellitesatellite, unlike the other , unlike the other largest KBO’s.largest KBO’s.

MAKEMAKEMAKEMAKE

310 year 310 year orbit.orbit. Reddish appearance, Reddish appearance,

possibly due to possibly due to nitrogen icenitrogen ice, , frozen frozen methane methane and and ethaneethane on its surface.on its surface.

Discovered on Discovered on March March 20052005; announced on ; announced on July 2005July 2005..

Formally classified as Formally classified as plutoid plutoid in July 2008.in July 2008.

MAKEMAKEMAKEMAKE

In the In the Rapa Nui Rapa Nui mythology of Easter mythology of Easter Island, he is theIsland, he is the

creator ofcreator of

humanityhumanity,,

the the godgod

of fertilityof fertility

MAKEMAKEMAKEMAKE

A Makemake carved on a rock

Dwarf planet discovered Dwarf planet discovered in in 20042004; accepted as a ; accepted as a dwarf planet on dwarf planet on September 2008September 2008..

Sort of a football shape Sort of a football shape ((ellipsoidellipsoid) due to its ) due to its rapid rotation.rapid rotation.

Extreme elongation Extreme elongation makes it unique among makes it unique among the TNO’s.the TNO’s.

HAUMEAHAUMEA

Mass 1/3 of Pluto’s.Mass 1/3 of Pluto’s. 285 year orbit.285 year orbit. Two moons:Two moons:

Haumea I Hi’iakaHaumea I Hi’iaka & & Haumea II NamakaHaumea II Namaka

Hawaiian goddess Hawaiian goddess of of fertilityfertility and and childbirthchildbirth..

HAUMEAHAUMEA

SmallestSmallest identified identified dwarf planet and only dwarf planet and only one in the asteroid belt. one in the asteroid belt.

Diameter of about Diameter of about 950 950 km km and is the and is the largest largest known known asteroidasteroid..

Contains Contains 1/31/3 the mass the mass of the Asteroid Belt.of the Asteroid Belt.

SphericalSpherical in shape. in shape.

CERESCERES

Believed to have a Believed to have a rocky rocky corecore, and possibly a , and possibly a liquid layer liquid layer below the below the surface.surface.

No known moonNo known moon.. The The DawnDawn space probe space probe

is currently visiting the is currently visiting the asteroid Vesta. This asteroid Vesta. This summer it will leave summer it will leave Vesta for Ceres, arriving Vesta for Ceres, arriving in February 2015.in February 2015.

CERESCERES

Named after Named after the the Roman goddess Roman goddess of of agricultureagriculture, , graingrain. . 

CERESCERES