an asteroid is a big
chunk of rock a lump of rock in space um
which is big enough to be
fairly readily observable but small
enough that no one wants to give it the
honor of being a planet but it's not
quite a planet and it's bigger than a
bit of dust obviously when you first
discover something you're very excited
about it you give it a name you come up
with a nice fancy symbol for it and so
for example uh the first minor planet
was discovered was ceres in 1801
and
ceres is a roman goddess of agriculture
and so it was actually given a symbol as
well as a name and the symbol it was
given was kind of a little sickle symbol
with a cross on the bottom of the sickle
uh making it like the the venus symbol
so a female agricultural symbol and so
when you're first discovering the first
of these you know obviously you have
time to think about it and you can come
up with a nice
uh appropriate looking symbol for it but
obviously as time goes on you more and
more of these things were discovered and
by the time you know they're up into the
tens to hundreds of them at that point
it starts getting a little silly trying
to come up with symbols for them so at
that point they sort of admitted defeat
and just started using numbers for them
all and now we're up to a quarter of a
million of the things that actually have
numbers that's obviously most of them
don't even have names let alone symbols
at this point you can see the the outer
planet and if you zoom in this is the
earth orbit and venus mercury
now i want to switch on the asteroids
and this is where all the asteroids are
so these are the asteroid orbits this is
of course not all
every asteroid there's millions of
asteroids and this is just you know the
biggest ones or the most famous ones and
i think it's around 40 or so that i show
so there is a a kind of a belt
of asteroids uh in the in the solar
system and it's thought to be
classically thought to be a kind of a
failed planet that all this rubble sort
of collected there and because of the
tidal influences of the other planets it
never all collected together to form a
planet so it stayed as this kind of
rocky rubble the first time we
got very close to an asteroid was in
1991
and so we went up to an asteroid called
gaspar and then in 1993 again we went to
ida
and this was the galileo probe and it
just went quite close to them as they as
it went on towards jupiter and
we didn't really know what they would
look like because we could only see them
with ground-based telescopes but they
look like
giant potatoes essentially they're not
spherical they're kind of elongated and
they have a bunch of pot marks in them
so it looks like other things have hit
them they have craters um so this is if
you look here this is the mars orbit and
this is the jupiter's orbit and then
there's this this asteroid belt where
most of the asteroids
actually orbit the sun it's kind of one
planet's worth of stuff that's kind of
spread out around the entire orbit so
actually the amount the total amount of
material although a planet's worth is is
quite a lot of material it's spread out
over a large space so actually no you
could fly quite happily through the
asteroid belt and the chances of you
bumping into anything are actually
pretty low because that was the other
thing i always wondered when i read
about probes like the voyages being sent
to the outer planets i always wondered
how they made sure they didn't hit
something in the asteroid belt
potentially there's a risk and of course
with a space probe you don't need
anything very big to hit it for
something bad to happen and so you know
the only ones we actually see the only
ones we have documented are the big ones
and so there is always a risk that that
any kind of space probe can run into a
chunk of rock out there in space
fortunately space is a very big place so
the chance of it happening really is
very low but it is a risk there's
nothing very much you can do about most
of the orbits you can see um if i tilt
it to the side
most of the orbits are in the in the
planetary plane
but there's some like this one for
example which is um tilted towards it
well i think most people will think that
they're interesting because there's a
chance that some asteroids could
actually hit earth so that's a bit
frightening and a bit exciting all at
the same time we can see
meteors meteor craters
throughout the earth there's some that
we've discovered with satellite images
and there's some that are just
completely obvious when you walk past
them there's a meteor crater in arizona
which is just fascinating never actually
been there in person but the photos are
incredible should we be scared of them
they have this reputation don't they
should we be afraid of asteroids yes is
the short answer i mean not very afraid
it's a classic problem in that the
chances of an asteroid smashing into the
earth during your lifetime is actually
pretty low
but if one did it could be
catastrophically bad
and quite how much you want to worry
about things where there's a very low
probability of it happening but if it
does happen it's very very bad
it's not really a well-defined problem
but yes potentially you know there could
be an asteroid that will come along and
wipe us all out do asteroids excite
astronomers or are they just rubbish in
between the interesting stuff depends
which astronomer you talk to if you talk
to a cosmologist they'll probably have
very little interest at all in asteroids
if you talk to somebody who's interested
in asteroids they'll tell you they're
the most fascinating objects in the
universe and with a kind of growing
interest in the formation of planets
it's pretty clear that asteroids are
sort of either the rubble left over from
when you've been building planets or
the sort of raw material from which you
might build a planet so actually you
know if you're interested in planet
formation studying asteroids is probably
some of the most interesting things you
can study
but there's a second asteroid belt so if
we zoom out basically and beyond neptune
somewhere one of these red ones is
actually pluto there's these are again
many many objects they orbit further out
in the solar system and this is called
the creeper belt um so this is this is
huge this probably goes out a few
screens or so by now
um for example there is sedna which is
quite a famous asteroid which is this
outer orbit i can zoom out a bit more so
you can see how vast that orbit actually
is i suppose most even people are
interested in asteroids probably would
would be prepared to concede that they
really are just lumps of rock the
interesting point is where they are in
the solar system uh what they're made of
how they might all come together to form
planets those kind of things so so
they're kind of providing clues to how
the solar system formed so individually
they're not that interesting just as you
know if you're studying a galaxy the
individual stars aren't particularly
fascinating
but it's the fact it's the kind of
viewing them as a whole and what they
mean for how planets might form it's
kind of the interesting question i think
the video game asteroids so this is a
game from
i guess the late 1970s
um where so
the quality of graphics was appropriate
to the late 1970s little line drawings
and you had this little spaceship
and so the idea then was to try and
eliminate these asteroids rather than
bumping into them what were you like
adam i got to be pretty good i'm ashamed
to admit
you