[Music]
this video looks at the characteristics
of the outer planets dwarf planets moons
and comets
to see the review of the inner planets
watch this video
the common feature of the outer planets
is that they are all gas giants they
have no solid surface
what we observe is a ball of gas or
vapour so we cannot land on them
there is a lot to take in so you may
want to pause the video to have a good
read
[Music]
which of the gas giants has rings
pause the video while you think of an
answer
the answer is that all four of them have
rings but only those of saturn are
visible from the earth
until 2006 a verse to recall the
planetary order could have been
my very elegant mother always jumps
sideways underneath pillows
in that year it was decided that pluto
was not a true planet and so was
reclassified as a dwarf planet poor
pluto
there are certain rules to be a planet
firstly you must be in orbit around the
sun
secondly you must be heavy enough to be
almost spherical in shape
and thirdly you have cleared your
neighborhood of rocks and debris
pluto joined other named dwarf planets
which are bodies that orbit a star and
have a stable shape
but have not cleared their orbit of
other debris
the large asteroid ceres is another
example of a dwarf planet and others
well beyond pluto are being discovered
a moon is a natural satellite
it's a body which orbits a planet
and so of course is part of the solar
system
as you will have seen some of the
planets have a large number of moons and
some none at all stop the video if you
want to go back and look
earth is unusual as our moon the moon is
large when compared to the planet in
orbits
it is thought that the moon was created
very early on in the life of the earth
after a significant interplanetary
collision which ejected rock which was
then captured in orbit
there are other objects that are part of
our solar system we rarely see
comets
people once thought the appearance of a
comet in the night sky was a warning of
a tragic event about to happen
comets are similar to large dirty
snowballs a few tens of kilometers
across
that follow a huge elliptical path
around the sun
that may take decades centuries or
longer to complete one orbit
it was sir edmund haley who was first to
successfully predict the return of a
comet that now bears his name
it returns every 75 years
and was last seen in 1986
you do the maths these ancient objects
only become visible when their orbit
brings them near to the sun
that's when a huge tale of vaporized
material is lit up by sunlight
notice that the tail always points away
from the sun as it passes by
showing the effect of the invisible
solar wind leaving the surface of the
star
before you go did you remember the verse
to recall the order of the planets