The
____________________
System
is
made
up
of
the
____________________
and
all
of
the
smaller
objects
that
move
around
it
.
Apart
from
the
Sun
,
the
largest
members
of
the
____________________
System
are
the
____________________
major
____________________
.
Nearest
the
Sun
are
four
fairly
small
,
rocky
____________________
-
Mercury
,
Venus
,
Earth
and
Mars
.
Beyond
Mars
is
the
asteroid
____________________
?
a
region
populated
by
millions
of
____________________
objects
.
These
are
left
-
overs
from
the
formation
of
the
____________________
,
4
.
5
billion
years
ago
.
On
the
far
side
of
the
asteroid
belt
are
the
four
gas
____________________
-
Jupiter
,
Saturn
,
Uranus
and
Neptune
.
These
planets
are
much
____________________
than
____________________
,
but
very
lightweight
for
their
size
.
They
are
mostly
made
of
____________________
and
helium
.
Until
____________________
,
the
furthest
known
planet
was
an
____________________
world
called
Pluto
.
However
,
Pluto
is
dwarfed
by
Earth
?
s
Moon
and
many
astronomers
think
it
is
too
____________________
to
be
called
a
true
____________________
.
An
object
named
Eris
,
which
is
at
least
as
big
as
Pluto
,
was
discovered
very
far
from
the
Sun
in
2005
.
More
than
1
,
000
icy
____________________
such
as
Eris
have
been
____________________
beyond
Pluto
in
recent
years
.
These
are
called
____________________
Belt
Objects
.
In
2006
,
the
International
Astronomical
____________________
decided
that
Pluto
and
Eris
must
be
classed
as
?
dwarf
planets
?
.
Even
further
out
are
the
____________________
of
the
Oort
Cloud
.
These
are
so
far
away
that
they
are
invisible
in
even
the
largest
____________________
.
Every
so
often
one
of
these
comets
is
disturbed
and
heads
towards
the
Sun
.
It
then
becomes
____________________
in
the
night
____________________
.
