it is quite amazing i mean usually so
this is a very big collaboration of
people and usually word leaks out
somewhere the sort of analogous thing
that happened not that long ago were the
first results about gravitational waves
and there there were kind of nods and
winks going on and if you knew the right
people then you could probably get a
little bit of an inside track
this has been absolutely nothing they've
really kept it
completely under wraps the data they're
going to be presenting today was
actually taken in 2017 so they've been
analyzing for the last couple of years
it's kind of the nature of this data it
is incredibly complex so actually
getting it to a point where you go from
the raw data to something that looks
like an impressive image is a lot of
work
and they so that would have taken most
of the last couple of years but at this
point they must know that they've got
something good so this thing called the
event horizon is kind of that point of
no return it's the point where you can
know even light can no longer escape
from from the region around a black hole
the region we would hope to see today is
a bit bigger than that it's probably
about two or three times that event
horizon size
really because well it's because the
distorting effects are so strong because
what we're actually going to see is sort
of light from around the black hole
radio wave light
and that radio wave light is originating
a little bit further away and also this
you've got this massive object in the
case of the one in the middle of milky
way it's about four million times the
mass of the sun which really means that
the piles of light you think about light
traveling in straight lines but because
the gravitational field is so intense
and the space-time is so curved the
light actually travels in very bent
paths technique they're using is the
thing called very long baseline
interferometry so the object that
they're trying to resolve
the the size of this the event horizon
is about 30 times the radius of the sun
so it's absolutely tiny at the distance
of the galactic center
and uh the region that they're trying to
see is a bit bigger than that but it's
still absolutely tiny the analogy that's
been drawn is it's like trying to take a
picture of a golf ball on the moon okay
so the technique the and
the technique they're using really
involves making the diameter of the
telescope bigger and bigger and so one
thing you can do is instead of having a
single telescope you have multiple
telescopes and then as you move them
further and further apart the sharpness
of the image increases because of the
the ultimate sharpness is limited by the
distance between your two most distant
parts of your telescope in the technique
they're using they're actually recording
the data on different radio telescopes
all around the world so d is enormous
it's the diameter of the earth is the
diameter of the telescope they're using
but then the tricky part is then having
collected all that data you then have to
combine it all together
and that's this the the technique that
they're using this thing called very
long baseline interferometry involves
taking all that signal um and actually
it's so they collect so much data it's
not something you can just transfer over
the internet they actually end up
recording the data on hard drives
shipping the hard drives to a place
where you can kind of correlate all that
data together and combining the
information from the telescopes to
extract an image from it so the trouble
is everyone has in their mind the movie
interstellar right because they had the
most amazing graphics of what one of
these super massive black holes would
look like um and they were actually you
know they had real physicists involved
in it there was actually lots of serious
general relativistic calculations went
into making those uh those graphics for
the movie of course the trouble is they
could do that at whatever resolution
they wanted we're limited by the
resolution that we can achieve with the
wavelengths that we have with the
diameter of the earth that we have which
really means that you're not going to
see those incredibly pinch-off images
the whole thing is going to be a bit
blurry
but hopefully it's going to be a blurry
image of something really exciting and a
blurry image of something really
exciting is probably pretty exciting
itself there is one other thing to
mention which is that there's another
candidate out there they're actually
observed two objects so they'll observe
the object in the middle of the milky
way um which is this black hole of about
four million times the mass of the of
the sun
they also were looking at the black hole
in the middle of a much bigger galaxy
messier 87 in the middle of the virgo
cluster um which is several thousand
times further away so actually the the
the quality of the images will be
several thousand times poorer because
you're trying to look at something
further away so everything's much
smaller but the black hole in the middle
of messier 87 is several thousand times
bigger than the black hole in the middle
of the milky way and it turns out that
uh event horizon size
scales with the mass of the of the black
hole so if you've got a black hole which
is a couple of thousand times bigger
uh in mass then it's it's event horizon
will be a couple of thousand times
bigger as well so the whole thing scales
up in size so it turns out the ultimate
sharpness of the image that they'll get
from the black hole in the middle of
messier 87 is about the same as from the
milky way
and it's a bit of a toss up which one's
going to make the nicer pictures
i think my betting's still on the milky
way because it's actually works that
when you do the calculations it works
out you end up with slightly sharper
images for the milky way but there's not
much in it
[Music]
galaxy m87
and this is the first level image of the
world
but these simulations are not sufficient
if you want to know what a black hole
looks like
um so
from our chatting before the press
conference i was wrong and i was right
i was wrong because i picked the wrong
black hole
i said they're looking at two the one at
the middle of the milky way and the one
in messier 87 and i thought they'd be
more likely to find something about our
one
but it turns out that this is the one
they got the result from today's
announcement was pretty special actually
because i've been working on black holes
myself
for 20 years i did my phd in black holes
i've been working on them ever since in
one form or another so today feels like
quite a profound day
and to make it even more special i was
watching the press release downstairs
uh with my six-year-old son
and uh he had his toy black hole with
him and he was sitting there comparing
it with the thing on the screen and it
does look more or less as we were
talking about before that there is this
kind of ring of fire effect
um that or more particularly you're kind
of not seeing any light from the middle
there and it really is just down to this
effect that the light is being so bent
by this black hole somewhere in the
middle there
that the light you're seeing kind of
coming out around the sides is are being
emitted around the back of the black
hole and being bent right round so i've
been bent by 90 degrees and more to head
towards us and into our line of sight
and that really is sort of the
definition of strong gravity right i'm
coming late to the party here it is
currently
2 40 nottingham time and it's been half
an hour since the results were released
in that time i've been interviewing
prospective undergraduates
and i actually made them sit down and
watch the press release up until the
point where we saw the image of the
black hole and then i i thought we'd
better get on with the business of the
the interviews he said yes it looks
looks like our toy black hole um but the
real black hole doesn't have eyes
and the real black hole isn't as cute
and cuddly as this one
and he said my toy black hole doesn't
have the ring of fire around it we know
that light gets bent by gravity this has
been known for actually almost exactly
100 years the first measurements of this
effect were made almost exactly 100
years ago when they were looking at what
happens during a total eclipse of the
sun where stars near the sun the
position of the stars shifts a little
bit just because the light from those
stars is being bent tiny bit by the
by the gravity of the sun so we've known
about this effect in kind of that weak
gravity limit that thinks light can get
bent a tiny bit by something as massive
as the sun now we're talking about light
getting bent through 90 degrees and more
and now you're talking about really
really strong gravitational fields so
that gets us very much into the einstein
end of general relativity if you were
just presented with a picture like that
and said what's going on
you could come up with many explanations
as to what it was that there's a there's
a cosmic donut out there in space or
there's a sphere and you're seeing the
edges of a sphere or whatever you know
there are lots of ways you could explain
there are many things in space that look
like rings
but the thing is here they said okay so
we think that general relativity is
right
and we think there's a massive black
hole in the middle of this galaxy and we
think that it's got a lot of this sort
of radio emitting material around it
what would we expect to see if those
things were the truth
and then they predicted this is what you
want to see pretty much
and then you go out and take the picture
and there it is and then so in some
sense that's the best proof there ever
is is when you actually predict
something before you go and see it
and so i think this in that sense this
probably is the best evidence there has
ever been
for a supermassive black hole in the
middle of a galaxy again there are lots
of ways that you can get those kind of
asymmetries the most likely i think
is that what's actually happening is
that the material is rotating it's not
it's not just sort of uniformly spread
around there it's actually spinning
around because we know further out
there's a disc of material which is
spinning around so the stuff we're
staying close to the black hole is
probably in a rather turbulent messy way
still rotating around and what happens
is the bit that's coming towards you
gets a big boost in energy there's this
thing called the doppler effect and in
light the way one of the ways that
manifests itself is that the light gets
a lot brighter there's a lot more energy
in it whereas the stuff that's going
away from you you see a
lower energy and so you basically see it
as fainter and so i think that asymmetry
we're seeing there is just to do with
the rotation of material around the
black hole i mean there's a lot of
structure there as well that it looks
like there's something that points out
this way as well which i'm kind of
intrigued by and again one of the things
that might be expected is you might
expect jets of material to be flying out
of the black hole
and the material would probably be
rotating around those jets of material
so it sort of fits together but again
that's kind of down near the
limits of what you can actually see on
an image like that but this i really
this is just my very first reaction to
it um so i am really looking forward to
reading about the science that's come
out of this about whether the structures
that i'm seeing in the background here
are real and what they mean
and just how these predictions match up
not just on a qualitative level but on a
quantitative level to the data that's
actually been gathered i mean the other
thing that you sort of have to take your
hats off to the people involved in this
experiment is you have to bear in mind
the technique they're using vlbi it's
not just like taking a picture with the
camera you've got to take all these data
from all these different radio
telescopes combine them all together
and from
that so basically you take sort of every
pair of radio telescopes and you get a
bit of information from the sort of the
phase delay the difference in the signal
between each pair and each of those
gives you a little bit of a picture but
actually you don't have the whole
picture and it is it's essentially
because you know if you've got a
regular camera you've kind of got your
lens or your mirror if it's a telescope
is sort of filling the entire aperture
in this case you've just got a few
dishes sort of scattered within your
aperture that means there's a lot of
missing information which means that you
then have to kind of reconstruct that
missing information
and they're actually
there isn't generally a unique solution
to this so there is a little bit of kind
of prejudice that goes into this that
says because you can you know there are
many different images you could
reconstruct from those data most of them
look completely ridiculous and so you
can sort of throw them out on the basis
that they look unphysical they're just
very noisy or they just
don't match what you'd expect from a
real astronomical object
and so there's sort of a lot of
processing that has to go into turning
this data into an image now what's going
to happen over time is that more and
more dishes get added to this network of
telescopes so you have more and more
pairs of telescopes which gives you more
and more information so as time goes on
they're going to be repeating these
experiments with more and more
information so the images will get
better and better and there'll be less
of that kind of interpolation of
figuring out the missing data just
because there'll be less missing data
but for the moment there's a lot of work
that has to go into turning
the raw data into an image like this and
so that's i think fundamentally the
reason why it's taken all the time from
when they took the data two years ago to
now to actually produce an image like
this from the data they collected so
there's talk about putting radio
telescopes into space because remember
what dictates the sharpness of the image
is how far apart your most distant parts
of your telescope are if you could put
your telescopes into orbit if you could
put one of them on the moon if you could
put them all into orbit around the sun
then in principle you can make longer
and longer bass lines there's not a lot
to this picture is there really
it's like you know it's a ring with a
hole in the middle but actually i think
that's absolutely astounding how amazing
is that that you know millions of light
years away you can actually see a black
hole in another galaxy down to the scale
i mean the black hole remember the
the black region in the middle it's
about three times the ultimate size of
the black hole itself so the black hole
itself is actually not much smaller than
this we really are getting right down
into that strong gravity regime right
next to the event horizon of a black
hole uh actually i said it exceeded my
expectations with simulations of what
this might look like and they look more
or less exactly like this but i thought
all with scattering of light and
instrumental effects and noise
you know they'll be lucky to get it to
get the prediction as accurately as that
but it looks
bang on so it's pretty pretty special so
yeah we're seeing this radio synchrotron
radiation from
the immediate vicinity of a black hole
you can see the black hole itself
shadowing
uh the light so you can see its
influence
um it's pretty special yeah that people
will be analyzing these data for years
to come i think so um
it feels like it does feel like a real
breakthrough yeah well i mean so
remember you're looking at radio waves
here so you can actually make this any
color you want it to be fundamentally um
and they've clearly just picked
something which looked nice you know you
could perfectly well have done it in
black and white or you know because
these are what you're really looking at
here are millimeter waves not optical
light at all so
yes there are there is a certain amount
of aesthetics as to what color you end
up reproducing these images in and it
makes a big difference that's the other
interesting thing that you know nasa
employs uh graphic designers who know
what looks really nice because you do
have that degree of freedom because it
is all about how you present the data
and you know it's not there's no
dishonesty here in that there is no
right color because as i say these are
radio waves radio waves aren't either
blue or green they're radio waves so
actually you really can pick whatever
color looks nicest if a galaxy is the
size of a football the supermassive
black hole in the nucleus is the size of
a hydrogen atom so they're absolutely
tiny
but the energy they can produce is and
they can
more than enough to blow the galaxy to
bits many times over so they
uh understanding the link between these
super massive black holes like the one
they found they announced today and the
broader galaxies that they're embedded
in i think that's a really key
issue for me personally it's an area i
work on how do galaxies form how do they
switch offs forming stars black holes
may play a role and now we know that
there really are black holes in there so
we knew that before but we've got an
actual image of one for the first time
so there's been loads of evidence for
black holes but no actual
image to take a picture of one so it's
pretty special
we've made quite a few videos about
black holes over the years
i'm going to put a link in the video
description and here on the screen also
our astronomy channel deep sky videos
we've got a video all about m87 already
on there so if you want to find out more
about m87 again links on the screen
video description