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it begins at a point in time nearly 4.6
billion years ago
a giant cloud of gas and dust floats
eerily through a remote arm of the Milky
Way chilled to more than 400 degrees
below zero when it's sitting there all
alone nothing much is happening in a
molecular cloud the temperatures are
very low the particles are moving around
very very slowly it's just sitting there
but if you have a nearby supernova an
exploding star it can send a shockwave
through this molecular cloud triggering
its gravitational collapse that collapse
is the first step in a long process that
brings the place we now call the solar
system into existence the evidence of
our past is all around us the four
planets in the inner part of the solar
system are made of rock and metal and
the four planets in the outer part of
the solar system are these giant balls
of gas so clearly different processes
were at play and that tells us something
about how we got here beginning is a
cloud of gas and dust the making of our
solar system will take 700 million years
now just two million years after its
birth the young system takes its first
steps in creating a family of planets
that one day will be as diverse as
Jupiter Saturn
or the earth
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for now though they are chunks of matter
continuing their rollercoaster ride in
the turbulence of the solar nebula the
thick rotating disc made mostly of
hydrogen gas is embedded with solids the
inner zone is filled with small chunks
of rock but outside the boundary known
as the snow line there are also ices of
methane ammonia and water which dominate
the outer disk and for good reason there
are all hydrogen compounds of one form
or another and hydrogen is the most
abundant element in that region of the
solar system at that point that abundant
hydrogen is combining with elements such
as oxygen to form the water or carbon to
form the methane or nitrogen to form the
ammonia and giving us those compounds
which are then freezing out continual
collisions amid the turbulence
make tiny specks of dust and ice stick
together through friction and static
electricity until they're large enough
for gravity to take over eventually they
become planetesimals planetesimals were
the original building blocks of our
solar system they're incredibly small
only about half a mile to a mile across
but there were countless numbers in the
early solar system
it was simply littered with them
these half-mile planetesimals will
eventually form full-scale planets but
of distinctly different sizes the
forming star had this huge solar wind
that was clearing material out of the
solar system Jupiter and Saturn were
fortunate enough to pick up most of this
material in their orbits which is why
they're so large Uranus and Neptune were
a bit later to the game and were unable
to pick up as much material which is why
they're smaller than Jupiter and Saturn
we are now at the most critical point in
the making of our solar system at 50
million years old
the protosun in its forming planets are
barely 1% of their present age
in many systems the central star doesn't
have enough mass to fully ignite but our
Sun is about to overcome that fate it
has reached the critical threshold of
heat and pressure where nuclear fusion
can begin in its core using the same
awesome energy that powers the hydrogen
bomb our Sun bursts into life as a fully
formed newborn star
at about 50 million years into the life
of the solar system since it first began
forming the Sun goes into a different
phase burning hydrogen actually doing
nuclear fusion at that point the Sun
becomes what we think of is now a fully
fledged star nuclear fusion will carry
the Sun into the distant future it will
burn long enough to support the
evolution of life on Earth
shining unceasingly for about ten
billion years
unlike the newly nuclear son the rest of
the solar system is far from mature 40
million years earlier the frozen gas
giants outside the snow line ceased to
grow and achieved an icy stability but
in the hot inner solar system where gas
is rare but rocks abound chaos still
reigns by the time that the Sun has
become a full-fledged star the planets
in the inner part of the solar system
are still trying to grow there are small
little proto planets that are building
together colliding getting larger and
larger eventually to become those four
big planets that we have in the inner
solar system
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