Download The Discovery of Planet X

Dwarf Planets and Kuiper Belt Objects
•
Dwarf planets
•
Pluto
Properties
The Discovery of Planet X
A
Discovered Feb 8, 1930 by then 24-year old Clyde
Tombaugh
Its existence was predicted by Percival Lowell using
the same techniques that Leverrier used to find
Neptune
Moons---Charon, Nix
and Hydra
Ceres, Pluto, Eris,
Haumea, and
Makemake
B
Kuiper Belt Objects
Resonant objects, Classical, Scatered Objects
Orbit: Pluto
Period 248 years
Semi-major axis 39.5 AU
e= 0.25
inclination of 17o to ecliptic
Physical Properties
Neptune Period=164.88 years
Distance= 30.1 AU
Locked in 3:2 resonance with
Neptune
248/164.88 = 3/2
Mass=0.002 x Earth's mass
Radius 0.2 x Earth's radius
Density
1.84 g/cc
Rotation
-6.4 days
Tilt
122o
Temp -223 C (solid methane)
Surface suggests solid ice covers the
planet (N2, CH4, CO).
This ice probably sublimates into a
thin atmosphere during the day and
falls a snow at night.
Pluto-Charon System
6.4 days
Discovered in 1978
Charon
6.4 days
Pluto
19,700 km
! ~ 35 % ice and 65 % rock.
! orbital period of 6.4 days ---identical to the rotation period of Pluto!
!Charon rotates once for each revolution just as the Earth's Moon
does the same side of Charon always faces Pluto
Pluto’s two other
Moons: Nix and
Hydra
Nix and Hydra have
circular orbits in the same
plane as Charon, but are
more distant from the
planet.
a series of eclipses (1985-1991) occurred provided detailed information
on the properties of size Charon
Radius
Mass=
(1/2 Pluto)
11.6% of Pluto
Kuiper Belt Objects
Nix
•The Kuiper belt contains objects with
an average distance to the sun of 30
to about 55 AU, usually having closeto-circular orbits with a small
inclination from the ecliptic.
Nix
Hydra
Hydra
Charon
Orbit Period
Charon 6.4 days
Nix
25 days
Hydra
38 days
Origin for all three satellites---a giant impact led
to the formation of Charon, Nix and Hydra
A vast number of frozen
bodies beyond the orbit of
Neptune, known as "The
Kuiper Belt."
These Kuiper Belt Objects
number in the millions, many
are the size of mountains to
the size of Pluto.
A dwarf planet is a celestial body orbiting the Sun that is massive
enough to be rounded by its own gravity but has not cleared its
neighbouring region of planetesimals and is not a satellite
More explicitly, it has to have sufficient mass to overcome its
compressive strengthand achieve hydrostatic equilibrium
Five dwarf planets:
Eris (.0028), Pluto (.0022), Haumea (.00067),
Makemake (.00067), and Ceres (.00015) ------- Mass(Earth Masses)
Kuiper belt objects are further classified
into the following groups:
Resonant objects---- are locked in an
orbital resonance with Neptune. Objects
with a 1:2 resonance are also called
twotinos, and objects with a 2:3 resonance
are called plutinos, after their most
prominent member, Pluto.
Classical Kuiper belt objects (also called cubewanos) have no such
resonance, moving on almost circular orbits, unperturbed by
Neptune. Examples are Quaoar and Makemake.
The scattered disk contains objects further from the Sun, usually
with very irregular orbits. A typical example is Eris.
(MAH-kay )
It is suspected 2000 dwarf planets may be found when the entire region
is explored.
Plutinos
Orbital resonances
These resonances occur when
Neptune's orbital period is a
precise fraction of that of the
object, such as 1:2, or 3:4.
New Horizons Mission to Pluto
Plutinos
2:3 resonance most heavily
populated with over 200 known
objects is the 2:3 resonance.
Objects in this resonance complete
2 orbits for every 3 of Neptune, and
are known as plutinos---Pluto is
among them.
The 3:4, 3:5, 4:7 and 2:5 resonances are less populated
New
Horizons
Launch 2006, arrive at Pluto by 2015. After Pluto, the spaceship will visit
one or more Kuiper Belt Objects
End of Chapter 13b
Uranus, Neptune, & Pluto
Go to Chapter 14a