Europa Clipper

Kuiper Belt, Dwarf Planets & the Oort Cloud

Kuiper BeltDiscovered in 1992Named for Dutch Astronomer Gerard Kuiper, who had PREDICTED its existence in 1951.Region beyond Neptune; 30 to over 50AUAt least 70 000 small, icy, slow-moving, objects

Dwarf Planets

And TNOs

The Problem of PlutoPluto was discovered in 1930. Named after the god of the dead.

Its position was predicted by perturbations in Neptune’s orbit

From the beginning it was unlike any other planet.

Its orbit is on a far different plane than the other planets, at a 17° angle from them and…

is so elliptical (30 – 49 AU) that

it crosses Neptune’s

orbit.

Pluto and CharonIts size is very small, less than half

Mercury’s radius and its mass is even less at only .002 of Earth

Its Composition was at first thought to be a terrestrial planet, though isolated beyond the Gas Giants, later its composition was discovered to be icy, more like a comet than Earth.

Its moon, Charon is unusually large, at half Pluto’s radius and orbits very close at 19,600 km.

All this made Pluto very unique until…

Eris, and a new type of planetIn 2005 another ‘planet’, called Eris after

the Greek goddess of discord, was discovered

It was very much like Pluto, a little larger with similar composition, a tilted (44°)

and elliptical (39 – 97 AU) orbit, and a large moon.

Recently more, (6+) other similar objects have been found.

In August 2006 they and Pluto were called a new category of celestial objects, “Dwarf Planets”

A Dwarf Planet:• Orbits the Sun• Has enough mass so that gravity

makes them roughly spherical• But have not cleared their orbit of

other objects

CeresOne Dwarf planet does have a

composition similar to Earth…Ceres

Located in the asteroid beltIt was once considered an asteroid it

orbits in the asteroid belt between Mars and Jupiter at 2.77 AU

It is between 909 & 975 km in diameter.

Dawn Mission

Trans-Neptune Objects (TNO’s) and other dwarf planets

Pluto, Eris, Sedna and Orcus are all icy dwarf planets that cross Neptune’s orbit or come close to it

At their greatest distance they pass into the Kuiper belt where comets orbit,

They are known as ”TNO’s” About 10 such objects are known.There are probably many more

dwarf planets orbiting far beyond Neptune.

Possibly 100,000+ over 100 km in diameter.

PlutoidsPlutoids are icy dwarf planets similar to Pluto.They orbit in the Kuiper Belt and in composition resemble comets.(Although exactly what gas the ice is varies)They Include: Pluto, Eris, Makemake

and HaumeaSome such as Sedna, Quaoar, Orcus and Varuna await a further observation

before determination

Pluto’s Transient Atmosphere

Nitrogen is especially common on Pluto

It has an atmosphere of mostly nitrogen that only exists when its closer to the Sun.

It freezes when Pluto reaches aphelion and vaporizes again as it approaches perihelion

Pluto and Charon are a “binary planet” because:

1. Charon has a radius (635km) more than half that of Pluto.

2. They orbit each other and are tidally locked so that both always face the same side to each other

Two true moons Nix and Hydra orbit the pair.

ErisEris, with a radius of 1200 km, is the largest of the Plutoids.It takes over 500 years to complete its 68 AU average orbit.It has one small Moon: Dysonomia

Makemake And HaumeaAt a radius of 950 km Makemake is the third largest

plutoid.Debate raged over the status of Haumea

Its elongated shape is the result of it fast spin.

At a period of 4 hours, the fastest known

So now it qualifiesIt has two small moons, Hi’iaka and Namaka

Oort Cloud

Oort Cloud

Hypothetical spherical cloud. No direct observations.Proposed by Ernst Opik (1932), Jan Henrik Oort (1950)50 000AU; defines gravitational boundary of solar systemSource of long-period Comets

Oort Cloud• Objects composed of ices (water,

methane, and ammonia)• 2 regions: outer sphere, inner

disc• Comets can not have formed on

their current orbit• Must be held in an outer

reservoir• Debris are redirected (as comets)

by disturbances, such as passing stars, collisions, etc.

Sources• http://www.lpl.arizona.edu/faculty/malhotra_preprints/ISP_Nov04/Kuiper

Belt.jpg• http://www.cnes.fr/automne_modules_files/standard/public/p1135_ed77

069b38b89947b9f6e5678e9af2adkuiper_pluton.jpg• http://discovermagazine.com/2004/nov/cover/outer-oort.jpg• http://www.myastrologybook.com/OortCloud10q8x7.jpg• http://en.wikipedia.org/wiki/Oort_cloud• http://en.wikipedia.org/wiki/Ceres_(dwarf_planet)• http://www.astro.ubc.ca/~lallen/kbo/general.html• http://www.enchantedlearning.com/subjects/astronomy/solarsystem/kui

per.shtml• Universe: The Definitive Visual Guide