we're going to talk about a star called
eater Kareem I eat a Kareem I yes is
that how it's pronounced that's how I
pronounce it it is a starling that's so
the reason why it's called eater is
because it's in this stellar
classification scheme where you go
through a constellation and you name the
stars through the Greek alphabet and so
eater left with the Greek alphabet and
Kareem I because it's in the
constellation of carina this is the
coolest star in the sky by a long way
you don't mean calling the astronomer
you don't know I mean calling the
amazing sense yes it is a truly
astounding object process of outside
chance it might kill us all so it's kind
of good to know about it's a star that's
kind of right at the end of its life
there's a possibility it's going to blow
up its possibility so what are you blown
up given that it's seven and a half
thousand light years away there's a
outside possibility that when it blows
up it'll create one of these gamma-ray
bursts there's an even more outside
possibility that gamma-ray bursts will
be pointed directly at the earth and
when that gamma ray bursts hits the
atmosphere it will fry that's a popular
story in fact if you hunt around the
internet you'll find that eater green is
going to kill us all but actually it's
not and so for various reasons firstly
almost certainly because of the nature
of the object when this thing explode
it's not going to produce gamma-ray
bursts and as you'll see from the
geometry of it we're pretty sure that if
there is a gamma-ray burst it won't be
directed in our direction anyway so no
it's not going to kill us it will be
pretty spectacular if it goes supernova
then it will be as bright as the full
moon when it goes for you know a year or
so afterwards so actually it will be a
pretty spectacular sight in the sky when
it goes but it's really not going to
kill us the guns probably not loaded and
even if the gun is loaded it's not
pointed at us actually so so we're not
looking down the barrel
we'll be fine we don't know a huge
amount about this star it's actually
quite hard to figure out exactly what's
going on and so observational E it's
hard to see what's going on
theoretically we really don't understand
these very last stages of a star's life
particularly well so the short answer is
yes it could go off tomorrow or it could
go off in 50,000 years time and we
really don't know which so this is what
this thing looks like so it really is
pretty spectacular looking object when
you point the Hubble Space Telescope at
it and the reasons for this weird
structure will come through in a second
but the stars come and somewhere down in
the middle there it's a slightly weird
star because actually it's very variable
and so it was when it was first
documented in the
18th century it was sort of a naked-eye
object then in the 19th century very
briefly became incredibly bright it
became the second brightest star in the
sky for the while second only to Sirius
and then it faded out of out of naked
eye sight entirely faded down again and
so it varies around a lot so it's
clearly there's something pretty
dramatic going on think we're stars
usually they sit around for millions
billions of years not doing anything
very much and the fact that this thing
is varying on a timescale of years tells
you that something pretty dramatic going
on in all this other stuff you can see
that the thing you can see around it is
called the homunculus nebula because
it's supposed to look like a little
person really see it myself but there we
go and what I don't know what a monk
Ellison means a small small person all
that stuff you see around it this
homunculus nebula is actually associated
with this massive brightening that
happened in about 1840 what's thought
the hand is the star almost exploded at
that point it almost went supernova and
in the process so there's a very massive
star in the middle there it weighs about
120 times the mass of the Sun and in
about 1840 it through threw off about 20
or 30 times the mass of the Sun so a
good fraction of its total mass got
thrown out into space and what you're
seeing there is that debris kind of
expanding away from the star could
easily have exploded entirely at that
point but it looks like it just lost
about 30% of its mass at that point is
this a common occurrence for stars to
have a sort of a not quite a near-death
experience I think it's the only one we
really know about I mean this is it is
very massive stars it's more than 100
times the mass of the Sun they're quite
rare and this is the closely the example
it's about it's only about 7 and 1/2
thousand light-years away which actually
you know sounds a long way but but
actually four stars that massive this is
a relatively nearby example of it
because they really are very few and far
between
what happens next does it does that does
it get another cracker or is it missed
its chance to go out in a blaze of glory
our understanding of these late stages
of stellar evolution are really
sufficiently poor that we just don't
know probably it'll blow up at some
point there's a further complication
which we'll come to which is actually is
not a single star it's got a companion
so there's another star around it so the
main star is about 100 times the mass of
the Sun there's another little star
which is only about 20 or 30 times the
mass of the Sun in orbit around it and
in fact these two stars as we'll see are
quite closely interacting which further
com
our understanding of what's going on
this is a two-dimensional view of this
star and you can kind of infer the
three-dimensional shape sort of just by
looking at it but the neat thing that's
been recently done is some astronomers
have figured out how to turn this
two-dimensional picture into a
three-dimensional picture essentially by
using the expansion of the of the lobes
because this material is all flying out
you can actually measure the speed at
which the different bits of it are
expanding by looking at the Doppler
shift in the light that's being emitted
and so you look at a particular spectral
line something that should be occurring
at a particular wavelength and you
should see how much it's blue shifted
already fitted to figure out how fast
it's moving and by making some
assumptions about how the things
expanding you can then turn that speed
into the third dimension in space
essentially because the further you are
away from the star the faster things are
moving so if you see something moving
very fast it's probably a long way from
the star if you see things moving more
slowly it's kind of closer to the star
so that sort of gives you that third
dimension and that allows you with a
some fairly clever analysis to turn this
into a three-dimensional picture what
this thing looks like this guy's
published a paper about this and so
here's their three-dimensional model of
what that expanding groups pair of blobs
looks like they also produced a 3d CAD
model for what they've done and so that
anyone who's got a 3d printer can go out
and print their own so we printed our
own star go Odyssey so here it is a 3d
printed version so I went to our guys
you know in the University of Nottingham
there's a group who do a thing called
additive manufacturing which is
basically figuring out really clever
things to do with 3d printers and
although this is not they're kind of
their main business they can 3d print
anything pretty much unlike you know the
usual
3d printers they can actually put in
lots of different materials as well so
they actually printed this out for me in
titanium this is a star printed in
titanium based on that 3d model of what
this exploding star looks like I have to
say this is far beneath their dignity to
do this kind of thing that actually they
can do the most amazing stuff there are
ultimate ambition these guys is they
want to 3d print a mobile phone which
works as soon as you take it out of the
printer so that's the kind of level of
ambition so you can see this is really
not pushing their technology
particularly hard we try and see if we
can orient it kind of the same way as it
is in it's going to be tough because you
know what were you're looking at things
from
it's just kind of something like that I
think from where you are thank you so
the main things you can see are those
kind of two lobes presumably the there's
an axis to the star of something to do
with its directional rotation probably
there was a kind of disk of material
around the star which stopped it from
expanding in that direction and
therefore it expanded sort of towards
the poles of the star these two lobes
you can see sticking out are the results
of that explosion kind of out along the
poles of the star but you can see
there's a lot of other structure as well
there were these little is a little
dimple in the end and this strange kind
of groove channel in the end here and
the other thing that they really studied
really for the first time of these two
bits sticking out to the side which turn
out to be might be telling us something
well the fundamental about the nature of
the explosion and this is the first time
they've really been able to see this the
sort of three-dimensional structure at
these strange wings sticking out to the
sign they printed out in plastic and
being able to look at it they actually
using this lots of uses for this this
actually allows you to study things in a
way that they've not been studied before
they're also very useful aids for
example if you're trying to explain
astronomy to blind people being able to
produce three-dimensional models of
things and so that they've become much
more tactile so they're useful from an
educational perspective as well but
actually you can learn things about the
structure of something just by being
able to look at it really in three
dimensions it's so much more somehow
more real when you have a little three
dimensional model or something rather
than just looking even animated on the
computer screen the other thing that's
interesting about this object it is is
it is a binary star that was actually
only discovered about ten or fifteen
years ago and the way that the easy way
that we know it's a binary star is
because actually things vary in this
thing in a periodic way every 5 and 1/2
years for example this object produces a
sudden burst of x-rays and so it's been
monitored over quite a long period of
time and they've monitored a series of
these x-ray bursts and what's happening
there is you've got these two massive
stars so one remembers about 110 solar
masses something like that
about probably 20 or 30 solar masses
each of those stars is actually
hazardous of strong stellar winds which
are these throwing particles off
throwing its outer layers off the whole
time and it's on there on a very the low
mass one lower mass one is on a very
eccentric orbit around the higher mass
one and so they kind of orbit around
each other and and you've got these
winds coming off them so the wind from
one smacks into the wind from the other
and you get this very intense
interaction where the winds collide with
each other form shocks get heated up to
very high temperatures and amid x-rays
and obviously when the thing which is
close to its closest approach the small
star approaches the bigger star you get
this sudden burst of x-rays because this
is something very strong the interaction
between the two and what happens is that
the the little a star has a lower
density but higher speed wind which kind
of clears out a cavity in the bigger
bigger star so you can see this is sort
of strange little spiral structure
appears but the more interesting thing
is that most of the time the structure
looks something like this that the
little R star is kind of cleared out a
region of the bigger star it looks like
pac-man eating a power pill so exactly
and but the interesting thing is that
how wide the pac-man's jaw is open here
which is about 120 130 degrees and the
direction in which this opening is
pointing because if we go back to this
little model for a second there are
these two little lobes sticking out to
the sides and the angle between them is
about 130 degrees and in fact the
direction in which they're pointing is
the exactly the same as the direction of
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