- [Instructor] At the
edge of the solar system
Pluto pushes the boundaries
of our understanding
of the universe.
Nestled within the far flung Kuiper belt
the dwarf planet is believed
to be one of the countless
celestial objects left
over from the formation
of the solar system.
While it is one of the
Kuiper belts largest bodies,
Pluto is only half as wide as
the contiguous United States
and about two thirds the
size of Earth's moon.
Making it easily dwarfed
by the solar system's
eight true planets.
This tiny world takes 248
earth years to orbit the Sun
and it does so from an average distance
of over 3.6 billion miles
or 40 times the space
between Earth and the Sun.
Such a distance from the solar
system's main source of heat
causes extreme temperatures
on the dwarf planet's surface
between negative 375 and
negative 400 degrees Fahrenheit.
The frigid temperatures
play a crucial role
in shaping the geological
composition of Pluto.
It's core, likely made of rock and metals,
is encapsulated by a mantle made of ice.
The dwarf planet's crust
is made of rock material
and other types of ice such as
frozen carbon monoxide,
methane and nitrogen.
These frozen gases cover Pluto's
approximately 6.4 million
square miles of surface area.
Which is barely the size of Russia.
The icy terrain is much like Earth's.
With polar ice caps,
valleys, planes and craters.
It even has glaciers
made of frozen nitrogen
and frozen water on the surface
makes giant floating mountains.
(peaceful music)
Such varied terrain is
influenced by the presence
of weather patterns or an atmosphere.
Pluto's atmosphere is thin
and reaches a high altitude
due to the dwarf planet's low gravity.
Which is only about 6
percent as strong as Earth's.
The atmosphere's comprised
of nitrogen and methane gases
plus red hydrocarbon particles
that scatter sunlight
to give Pluto blue skies.
Parts of the atmosphere may
even freeze and fall like snow.
Floating high above the
dwarf planet's atmosphere
are five moons.
The largest, Charon is about
half the size of Pluto.
The four other moons;
Nix, Hydra, Kerberos and
Styx, are much smaller.
While the eight true
planets were discovered
by the mid-1800s.
Pluto was not spotted until 1930.
Pluto, named after the
Roman god of the underworld,
was considered the ninth planet.
But in 2006, Pluto lost this status.
At the time, worlds similar to
Pluto were being discovered,
deeper in the Kuiper belt.
This initiated close scrutiny of Pluto
and the definition of a planet.
The International Astronomical
Union evaluated Pluto
based on the characteristics
necessary to be a true planet.
It must orbit the Sun.
Is not a moon and has enough
mass and gravitational pull
to assume a round shape.
However it was the fourth characteristic
that compromised Pluto's status.
It's inability to clear
it's orbit of debris.
So Pluto was reclassified
and arguably demoted
from being a true planet
to being a dwarf planet.
Pluto's story represents
our evolving understanding
of the universe.
There is always more to discover
and we are continuously
reaching toward it.
