Download The Solar System At least 7 billion miles across, home to 8 planets

SCIENCE
The Heliosphere
ESO level 1
Apendix 5
The Solar System
At least 7 billion miles across, home to 8 planets, 166 moons, and billions of asteroids, comets and meteorites.
But in galactic terms, this is our local neighborhood. Welcome to Space School!
Today’s topic:
At 4.6 billion years old, is the solar system. Its planets, including our own Earth, formed out of what was left
over after the birth of the sun. Amazingly, these 8 massive, celestial bodies grew out of tiny specs of dust
orbiting the new star. Time and again the young planets collided with floating debris, eventually reaching their
current size. The sun’s gravity then locked them into orbit. The solar system is divided into two distinct regions:
Mercury, Venus, Earth and Mars make up the inner solar system while Jupiter, Saturn, Uranus and Neptune
make up the outer solar system. The four planets of the outer solar system make up 99% of the known mass
orbiting the sun.
It was in that distant region of the solar system that in the year 2006 astronomy was shaken to its very
core. After almost 80 years Pluto lost its status as the ninth planet. The International Astronomical Union
couldn’t ignore findings that similar, even larger bodies than Pluto, traverse the outer solar system. Forced to
define the term for the first time, astronomers established three distinct criteria to earn the name “planet”. First
the object must orbit the sun. Second it must have sufficient gravity to maintain a planet’s spherical
shape. Finally, after millions of collisions the body must have cleared away other objects from its own orbital
neighborhood. This last point is where Pluto fails, so it’s been demoted to a dwarf planet, and joined two other
dwarfs, Eros and Series. Astronomers believe there may be as many as 42 dwarf planets in our solar system.
Pluto and beyond is not simply the beginning of endless, open space, but the inner edge of a gigantic region
filled with asteroids, comets and meteorites. Billions of miles beyond our sun stretches the Kuiper Belt, an
area larger than our entire planetary system. It’s home to most of our solar system’s comets: icy, flying
rocks. There are more than 3,350 known comets in our solar system.
Further out still is the Scattered Disk, a belt of strangely orbiting objects, often small and icy minor
planets. Finally we reach the Heliosphere, an immense, magnetic bubble which forms the outer edge of the
solar system. This area is thought to be the boundary between solar and interstellar winds, the boundary
between our own neighborhood and the great expanse of interstellar space. For us the solar system seems
enormous, its distances almost beyond comprehension. But incredibly it’s just a tiny corner of the giant Milky
Way Galaxy. Still, despite overwhelming odds, we humans have set out on a journey of exploration. We are
sending one spacecraft after another into the farthest reaches of the solar system, all on a quest to understand
our place in the universe and the mystery of the great beyond.
This is Space School signing off. Class dismissed.
Francisco González Moreno [email protected]
Francisca Jurado Lorente [email protected]
CEIP DUNAS DE DOÑANA
MATALASCAÑAS (HUELVA)
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