how do i pronounce this star well that's
a good question so i ran a twitter poll
and the answer is nobody seems to know
well you're an astronomer what do you
say when you're an astronomy conference
and someone says so professor merrifield
what do you think about the latest
happenings on vids uh i
i don't go to that kind of conference
because i don't do stars it's difficult
because it's a corruption of an arabic
name so actually quite how you're
supposed to pronounce a corrupted arabic
name i'm not sure
so you can really pronounce it how you
like but let's go with beetlejuice shall
we it's a star it's a relatively massive
star about 10 times the mass of the sun
it's if you look at the constellation of
orion which is one of the few that most
people recognize is the star at the top
left of her orion and the reason why
everyone's excited about it is because
it's fading at the moment quite
dramatically and the other interesting
fact about it is that in astronomical
terms it's likely to blow up sometime in
the near future and people have kind of
put these two facts together and equated
the fact that it's fading at the moment
as a sign that is about to go wow
is it about to go i think it's unlikely
so i i was a bit careful in what i said
in that i said in astronomical terms
it's going to go pretty soon and that
just basically means it's probably going
to blow up sometime in the next 150 000
years so the chances of it being
tomorrow are pretty slim i would say
he's actually
well documented as a variable star it
has some sort of quasi periodic things
there's a longish time scale variation
there's a shortage timescale variation
so there's lots of variability going in
it on in it
it is a complete mess and so actually
although this is the faintest it's been
in recent times it's not really
unprecedented for it to be fading if and
when it does blow up will that be
preceded by a sudden and dramatic fade
nobody knows because no one's ever seen
one of these things that close up and
seen it before it blew up to know what
it's going to do
so
no one really quite knows and the reason
part of the reason why no one knows is
because it really is a very messy system
it's big extended bloated kind of thing
there's all sorts of processes going on
in it so quite what the sequence of
events would be that you'd actually see
from the outside
is really something of a mystery at this
point
i thought we modeled stars all the time
and we've got all these theories about
what the explosion looks like and how a
supernova works and like it will
supernova presumably it will be a
supernova
and yeah you're right you know we sort
of have a broad brush understanding and
the sort of the physics that's going on
but it's like you know it's like the
difference between climate and weather
right that actually even if you think
you know what's going on in the climate
you don't know what tomorrow's weather
is going to be like and really what's
going on in the outer layers is very
much the weather and the the the climate
is the explosion that's going to occur
right in the core of it and how these
two things are coupled together is
really quite complicated so we really
don't know what you'd expect to see in
the days months years leading up to the
explosion because before
this beetlejuice stuff if you'd asked me
brady what do you think happens to a
star in the year or two or the week or
two before it blows up
i would have said oh i bet it gets
really really bright
and if you'd asked me the same question
i'd probably have said the same thing
you'd think that that would be the what
would be going on but as i say it really
is because what's going on right in the
middle where there are probably are some
pretty frantic nuclear processes going
on right in those dying days of the star
and what you actually see in the outer
parts are really only very loosely
coupled together so it really isn't that
clear what you'd end up seeing in those
last few weeks but you think
like if you're a betting man
i'd be prepared to put a fair amount of
money on it not going in my lifetime
which would be a shame because i'd love
to see it but no probably not all right
it would do a bit of a job of an
astronomy for a while actually because
when it does go it's going to be
brighter than the moon or about as
bright as the moon and so the kind of
astronomy i do i tend to do away from
full moon
and it's going to be like having another
bright light up there this is almost as
bright as the full moon so for a year or
so the kind of astronomy i like doing is
going to be quite hard to do because
there'll be this new bright light in the
sky elon musk will ruin the sky by then
that's true yeah
and i'm you know for the dramatic for
the drama of i'm getting to see your
star blowing up i'm prepared to put up
with not doing my kind of astronomy for
a year i think
you said you'd be willing to put money
on it not being in your lifetime
they should run markets on astronomy
events don't they they don't really ever
do that do they i've never like you can
bet on everything can't you can bet on
who's going to be the next prime
minister and who's going to be there
they should have bets on astronomical
events i bet you could you know if you
wanted to i'm sure your local bookie
would be able to figure out some odds
for you if you wanted to i actually have
an astronomical bet which has been
running and i don't actually know i
don't know where the betting slip is so
i can have to find it one of these days
which is that i put a bet that they
would find
life on mars years and years and years
ago and and it was quite an interesting
process actually because i i went to the
bookmakers and they obviously they
couldn't do anything there and then but
then they they have specialists right
and they put you in touch with their
specialists and i had a chat with a
specialist i had assumed that they would
like insist there being some time limit
you know that you find life on mars
sometime in the next 10 years because
otherwise it's just a bet that goes on
and on forever but actually it turns out
they don't care because they get to keep
your money until the bet's settled so i
have this bet that they will find life
on mars and there were various criteria
like it had to be non-microscopic and
those kinds of things so bacteria
wouldn't count and those kinds of stuff
um so what were you thinking you weren't
thinking little green men i i reckon
well i i didn't know what i was thinking
really i just thought it was a fun thing
to find out whether you could put a bet
on finding life on mars or not rather
than actually thinking they'd find
anything um and i think i i'm trying to
remember the exact terms it didn't
actually have to be alive so they could
find like fossil remains
so as long as it wasn't like microscopic
that then uh then it would i would win
the bet but i have to find the betting
slip one of these days to find out do
you think you're going to lose that bet
or do you still think you might win that
is a winning i reckon there's still a
chance all right yeah it's still it'll
maybe it'll pay off
you know i think
you know mars was a much nicer place a
long time ago and you know there was
water around there was an atmosphere
and so yeah who knows maybe there was
like
when beetlejuice does go yes do we know
any is there anything
will we get any clues that it's about to
go we will get a little bit warning so i
was intrigued by this in that i heard
various stories about whether we get any
advance warning or not and the answer is
we will and so i found a paper
that was published a couple of years ago
neutrinos from beta processes in a
pre-supernova probing the isotopic
evolution of a massive star they do a
calculation of what the last few hours
of a star's life is like just before it
goes supernova remember the way a star
is powered
is it burns the various uh chemical
elements from one to the next so by
nuclear fusion it will turn hydrogen
into helium and then helium into carbon
and so on up creating heavier and
heavier elements
and the problem with doing that if
you're a star
is that each time you get less and less
bang for your back you know each the
hydrogen to healing processes you get
quite a lot of energy out helium to
carbon a bit less and so on and each
time you get less and less energy out
which means that in order for the star
to kind of hold itself up it has to burn
things at an ever more frantic rate in
order to do so so the last stages of
burning are really very intense but not
very energetic they don't actually
produce much energy and they don't last
very long because it uses up the fuel
very very quickly
and so this is looking at those last few
stages and asking you know what are the
processes and actually more importantly
is there anything we could detect that
would tell us that those processes were
going on
and in particular the thing that we'll
get straight out from the star are the
neutrinos so one of the byproducts of
lots of nuclear reactions
is that you produce these pathetic
little particles called neutrinos
basically whenever you turn a neutron
into a proton or a proton into a neutron
in some process
you tend to produce one of these
neutrinos and neutrinos are such
wimpy little particles that they'll
actually travel straight through the
star
and so they don't really care there's a
whole body of a star around it so any
neutrinos that are produced will stream
straight out
and what these guys did is they did some
calculations as to say how many of these
neutrinos are there and in those last
few frantic hours when you're burning
all these things as quickly as you
possibly can turns out the processes are
so intense you make a lot of neutrinos
so star spends all that time burning
fuel
and
over millions of years but the final
fuel event is something measured over
hours hours yes literally hours so and
it really is that frantic that it's
desperately trying to stay alive and so
it's using up all the fuel that possibly
can it's quite sad almost it's pathetic
really it's like it's drowning yeah no
it really is this frantic oh my god oh
my god i've got to keep going you know
it keeps burning all these things and
eventually you know it just runs out of
things to burn so they do these
calculations they figure out how many
neutrinos get produced
and so here they are this is the number
of neutrinos being produced per second
and so they did a couple of calculations
15 solar masses and 30 solar masses
beetlejuice is around probably around 10
but so this is reasonably close to the
kind of thing that would be going on in
betelgeuse and you can see this is the
luminosity in the number of these things
being produced per second and you can
see as it's coming up towards the end
here these curves are all going up and
up and up and up this is one hour before
the thing goes we're looking at 10 to
the 52 neutrinos being produced per
second
so it's a huge number of neutrinos
then of course they spread out through
space so by the time they get to the
earth there's many fewer of them and
then you need a neutrino detector and
that's a hard thing to do because
neutrinos just pass straight through
everything and so stopping neutrinos
detecting neutrinos is a hard thing to
do but we have some neutrino detectors
on earth and they're mostly designed to
do things like detect neutrinos from the
sun but it turns out that we might
actually hope to detect some of these
using the earth-bound neutrino detectors
so they go through that bit of the
calculation as well to figure out what
you'd actually expect to see so they
looked at various neutrino detectors
june and juno don't actually exist yet
so they're ones that are being built at
the moment supercamioconda is one that
does exist now
and they add up all the neutrinos you'd
expect to detect and they reckon you
detect slightly less than half a
neutrino which doesn't sound too
promising
until you realize that this calculation
was done assuming a star that was about
five times further away than beetle uses
and so the number of new so the
neutrinos spread out through space they
kind of fill the whole area which means
that the number of neutrinos you detect
decreases as one over the distance
squared so if the thing's five times
closer that means you see 25 times as
many neutrinos so while half a neutrino
turns into about 12 neutrinos
that doesn't sound very many but
remember that the only previous time
we've detected neutrinos from a
supernova was when the supernova went
off in 1987 in the large magnetic cloud
and there they got very excited because
they detected 10 neutrinos
so this is kind of in the ballpark that
people are used to detecting from
neutrinos and getting excited about when
they detect them um so actually it will
sort of set off the neutrino alarms when
it happens and they will actually have
this advanced notice they even i think
have some directional information so
they'll even know that these are
neutrinos that came from the general
direction of beetlejuice is there a
system in place for
the detector to tell all the telescopes
to swing around and point at beetlejuice
i'm not sure there is um and actually
i'm not sure they can process the data
that quickly whether that whether it
would only you'd only find out after the
fact which is what happened with
supernova 1987a they actually only found
out afterwards that actually yes we did
detect it in neutrinos
the good news is if it hangs on for a
few more years these other neutrino
detectors come online and you can see
that actually where supercamioconda is
only detecting half a neutrino the juno
detector will detect 17. so and again
remember that will go up by a factor of
25 just because it's closer than that so
if we wait around until juno is online
then we'll detect lots and lots of
neutrinos and that really would be a big
burst that would be
set off some alarms i suspect you talk
about advance notice but that's not
because anything bad will happen if
beetlejuice blows up not to us no we're
far enough away that actually all you'll
see is a nice big bright light in the
sky um but it's not you know the gamma
rays or anything like that aren't gonna
kill us from uh beetlejuice when it goes
how far this is a long way away isn't it
so this is like all stuff in the past
yes it's uh it's 700 light years away so
yeah it could have gone by now and we
might have to wait around for a few
hundred years for the event to get to us
the neutrinos travel to earth at the
same speed as light so like it's not
like the explosion will overtake the
neutrinos no and in fact because and
because there'll be neutrinos created in
the explosion itself and again a really
really big number of neutrinos so
actually this is the sort of
pre-supernova stuff but when the
explosion really goes there'll be a huge
burst of neutrinos and actually they
will get to us before we see the light
because the neutrinos come streaming
straight out but you've got to have this
explosive shock wave has got to work its
way through this uh the body of the star
before we actually see the the light of
the supernova so in fact when the
supernova goes we'll get a little bit
more warning that the neutrinos will
arrive before the explosion does
but earth is safe so i mean something
that far away it's not like that we're
going like there's going to be any
warmth heading towards earth that's
going to cook us or no it really won't
or as i say all we'll see is it will be
a dramatically bright light in the sky
but nothing's going to fry how dramatic
will you see it in the daytime and it'll
be visible in daytime it'll be about the
same brightness as the moon so visible
in during the day
for and i think you'll see it during the
day for a matter of weeks or months and
it'll be visible to the naked eye for a
year or so
awesome
has there ever been a supernova
in our
galaxy that we've observed
not in recent times i mean there were so
the chinese records has uh records of
supernovae around a thousand years ago
so there have been supernovae in the in
the milky way
crab nebula was one of those exactly the
crab members one the only one that sort
of in in recent times was supernova
1987a which was in the large manchester
united cloud in our near neighbor rather
than actually being in our galaxy
okay ah i'd love to see one it would be
pretty cool you should call the
bookmaker and find out what odds they'll
give you on beetlejuice going yeah
probably not very good at the moment
because there's been so much noise about
it
you didn't see the picture you didn't
see what building you know
what's that you've got yeah so here's a
picture this is what beetlejuice just to
give you a sense of what a supergiant
star actually looks like this is a
picture of beetlejuice it's sufficiently
big
that with the very high resolution
telescopes that we have like the atacama
large millimeter array where we can see
exquisite detail we can actually make a
picture of the disc of the star itself
and that's partly because this telescope
can make incredibly high resolution
sharp images but it's partly because the
thing's enormous in that somebody's
drawn on here what the orbits of the
planets in the solar system would be and
you can see that actually it's bigger
than the orbit of jupiter
it's a truly enormous object the other
thing you can see about it is it is a
complete mess right that actually is not
a nice
uniform sphere there's a bright patch
over here there's indications that it's
not even exactly round that's because it
is this very sort of
churning convective system it has huge
convective cells there's things rising
things falling things being spat out
that actually it's a very uh non-relaxed
system and that i think is probably what
lies behind the current fading that
there's one of these
phenomenas going on that's just maybe
it's spat out a load of dust or
something which is currently obscuring
it so we're all we're currently seeing
is just some one of these processes
that's going on in the outer layers of
the star
which just just made it fade in this
rather dramatic way
do stars this big have planetary systems
as i understand them like do they well
if this one i mean it might have had
remember this is in its supergiant phase
before that it was a you know a regular
sized star so if it had a solar system
like the earth
it would have been
eaten up by now
so somewhere inside beetlejuice might be
like the remains of civilizations well
fried at this point i suspect yes