- [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.