it's that time of the year again it's
the nobel prizes always charge my phone
up you
you never know do you but uh again
overlooked yeah i just
need to check the number
i called it yes i'm feeling a bit smug
about this because about five minutes
before the announcement i suddenly had
this feeling who was going to win and
sure enough they did or at least they
won half the prize anyway and the other
half of the prize went to a guy called
jim peebles a good call to see jim
peebles get half the nobel prize he's
regarded i think as the father of modern
cosmology did you put a bet on or
anything i should have done shouldn't i
really yeah
but no i didn't i
and it was literally five minutes before
the announcement it wasn't that clever a
prediction because i was certainly
wasn't the only person predicting it and
it's they've been sort of one of the
runners and riders for a number of years
now but i sort of thought it was their
time it's a slightly strange
uh award and actually so the citation
reads was awarded for contributions to
our understanding of the evolution of
the universe and earth's place in the
cosmos
which could be pretty much for anything
really because that covers pretty much
everything there is but jim peebles is a
cosmologist
and he's really one of the towering
founding figures of modern cosmology in
that he did a lot of the work he was
part of the group that was
predicting the existence of the cosmic
microwave background he did a lot of
work about the growth of structure in
the universe
the impact of dark matter on how
structure would grow so really i mean he
is if you if you teach a course on
cosmology in large part you're talking
about his work the model which is
fitting the data so well
has his
influence on every single part of it he
is a theorist but he's one of those
theorists who actually maintains a very
close link to the observation so some of
his work you know has actually he's
written papers which are presenting
observational data but more in a fairly
theoretical framework so you would think
of him as a theoretical astrophysicist
he's just demonstrated that in modern
cosmology these are the key ingredients
we look like we need and he he was there
at the start of each one of them playing
a role so he can be i think properly
regarded as the father of the subject
and
the expert
says that they're on your board
oh yeah father of modern cosmology yeah
that's what i decided to comment i did a
tutorial today we we have tutorial
system here at nottingham where all the
first years get to have a
there's usually six in the group i
screwed up i had to do 12 because and so
i thought well you've got to tell them
about the nobel prize or at least the
bit i know about it
if you were talking about jim peebles
you wouldn't say ah he did so and so
because there is just so much he's
contributed so the other half of the
prize was shared between michelle mayor
and didier kalo and they worked on
studying exoplanets they still work on
studying exoplanets so planets outside
the solar system
and it was awarded for and let me get
the exact wording here for the discovery
of an exoplanet orbiting a solar type
star so it was really their discovery in
1995 was what kicked off the entire
field of exoplanet studies because like
exoplanets these days are like candy
aren't they they're like you know
there are many many thousands of them at
that point there was only one actually
that's not quite true because there were
other planets and that's it's
interesting the way they worded the
citation it says an exoplanet orbiting a
solar type star the first exoplanet was
actually found uh orbiting a pulsar a
neutron star rotating neutron star which
is a very weird system and no one really
expected to find planets around pulsars
and so it was clearly something very
strange and so although it was
interesting it was like everyone was
well it's nothing like the solar system
so it's not really a planet in the sense
that we would understand it
there were also tentative discoveries of
planets orbiting giant stars that
preceded uh the mayor and kelo discovery
but this was really the first
announcement of one which we would sort
of equate with something like the solar
system so it was a solar type star very
like the sun with a planet in orbit
around it do you happen to know like
what star it was it was obviously a
nearby
uh it's 51 pegasus is the star and the
planet's called 51 pegasus b it's about
50 light years away it's very ordinary
star as i say it's a g-type star so very
like the sun a little bit more massive i
think 1.1 times the mass of the sun's a
tiny bit more massive but really
almost a twin of the sun very bulk
standard kind of style what method did
they use to
just discover it so they use this uh
radial velocity method i mean there are
now a whole slew of methods that are
used for discovering and studying
exoplanets but one of the the
foundational techniques and the one that
made this first discovery was this
radial velocity technique where if
you've got a star and you think of a
planet in orbit around it the sort of
simple picture is the star is stationary
in the middle and the planets orbiting
around but of course they're actually
tugging each other and sort of orbiting
around their mutual center of gravity
what that means is that the planet is
tugging the star backwards and forwards
as well as the uh the star tugging the
planet backwards and forwards so the
star is actually oscillating and so
sometimes it's moving towards you and
sometimes it's moving away from you and
by studying the spectra of the star and
looking at those little dips where there
are spectral lines in the star you can
see whether they're being shifted
doppler shifted towards the red end of
the spectrum or the blue end of the
spectrum so you measure that backwards
and forwards wobble of the star and that
gives you a measure of the mass of the
thing that's orbiting around it as well
as how rapidly it's orbiting around it
by how quickly the thing oscillates
backwards and forwards you know that's a
that's a good method i imagine i imagine
that method had been thought of for
quite a while and all the astronomers in
the world have access to telescopes and
telescope time
what did these scientists do that made
them a would be first like what what
method or trick or idea did they have
that made them the winners
so there's a couple of aspects here
firstly people weren't really looking
that hard at the time
because there was no expectation that
you'd actually be able to detect much
because we had this and so if you think
about what's easy what's easy to detect
in this case you want something where
there's a strong gravitational pull
between your planet and the star to tug
it a long way so it's got to be a big
planet so there's two things you want it
to be a big planet so it's massive so
it'll take the thing backwards forwards
and actually you want them close
together so the pull of gravity is
strong so that the movements are bigger
and so what you'd really want is a
planet like jupiter close to the star
now at the time we only knew about one
solar system and jupiter in our solar
system is a long way out as is the way
with scientists you know if you've only
got one example of something you
convince yourself that that's the way
the universe works so we had all these
ideas at the time back in the 1990s and
before that actually jupiter-like
planets only existed in the outer
reaches of solar systems and things
close to their stars were all little
things like mercury and earth which you
wouldn't be able to detect
and so because of that there wasn't
really a huge expectation that we'd be
able to detect this kind of effect and
what these guys actually found was
something that's about half the mass of
jupiter very close to a star
and so actually and subsequently of
course we found many of these hot
jupiter-like planets so jupiter-like
planets which are close to the star and
so it turns out that actually the
universe doesn't work the way we thought
it did back then and there are
mechanisms where even if a
big planet forms a long way out in a
solar system
there are mechanisms by which you can
kind of migrate inwards towards its star
so they found something that no one was
really that much expecting to find
which is why there wasn't a huge rush to
try and find these things the other
thing is they had some very clever
instrumentation they actually built a
custom built spectrograph that allowed
them to measure very small doppler
shifts they were down at sort of tens of
meters per second that they were
measuring these wobbles in these stars
which did require very good
instrumentation very stable
instrumentation where you can actually
calibrate things with that kind of
accuracy to really measure those very
small shifts so you couldn't have just
had like an off-the-shelf night of vlt
and have found it sort of thing like you
probably could now with vlt but in the
1990s no you really wanted a
custom-built instrument it wasn't on
that larger telescope it was i think it
was a two meter telescope so even by
then those standards the standards of
the 1990s it wasn't a particularly huge
telescope but it was just a very clever
spectrograph and they were looking for
something that no one else was really
looking for
as an astronomer
and you're an astronomer in the 90s i
was yes do you kick yourself and think
oh i could have done that that would
have been like a week's work and i could
have i could have been the one to find
it so the interesting thing is
before
their paper in the 1990s in the 1980s
let me show you another so let me show
you their paper so here's their paper
published in 1995
a jupiter mass companion to a solar type
style
nobel prize right there and it's you
know it's actually
not a particularly long paper it's not
got many pretty pictures in it a few
graphs
not even a picture of the star even a
picture no nothing spectacular about it
at all i mean you know nice looking data
here's the so here's the
the wobble backwards and forwards of the
star
so sometimes it's going away from us
sometimes it's coming towards us and you
can see so here's the scale 50 meters
per second so there's small shifts that
you're actually measuring here so that's
the wobble that they were measuring so
here's the interesting thing that was
the 1990s in 1989 this paper came out
the unseen companion of telephone number
a probable brown dwarf and it turns out
they had actually also discovered a
jupiter-like planet he's on there as
well there he's actually myo is on there
as well so he's one of the authors but
the the primary mover this guy called
dave latham was actually in an office
just over the corridor for me at the
time because i was a phd student and he
was a proper serious scientist at that
point
at the cfa in boston he wasn't very
excited about this result i mean he was
a bit excited but he was actually you
know because and again it comes back to
the fact that no one was expecting to
find planets
and the reason why he didn't know that
he'd found a planet so brown dwarfs are
sort of one up from planets they're sort
of failed stars and no one was you know
people were expecting to find brown
dwarfs because we find binary stars
quite a lot of the time and they have
different mass ratios and it wouldn't be
terribly surprising if once in a while
the littler one turned out to be not
quite making it as a star so people were
not that surprised to be finding stars
with brown dwarfs in orbit around them
because they're basically just
very closely related binary stars that
we know exist like a failed binary it's
a one half of it's kind of failed to
ignite so one half is a star the other
half didn't quite make it because they
weren't expecting to find planets he
convinced himself he hadn't found a
planet and the reason why there's an
ambiguity because you might think well
you know we know what mass is brown
dwarfs are we know what massive planets
are wouldn't he have known turns out
there's an ambiguity in this method and
the ambiguity in this method is i kind
of drew this you know when i was waving
my hands around i did it like that but
we don't know whether the system's like
that or whether it's sort of i can't do
it that way that way
like that and of course if the planet's
orbiting that way you don't see the the
star is still moving
but it's being tugged in the plane of
the sky so you don't see these doppler
shifts so this is ambigu and of course
you can have anything in between
so actually if you see a certain
movement it could be like uh if it's you
know you see a certain movement it could
be a relatively low mass thing that's in
the plane of the sky so we're seeing all
the movement of the star or it could be
it's almost in the much more massive
thing and actually this thing's really
jerking around all over the place but we
don't see most of the motion because
most of it's in the plane of the sky
rather than towards us or away from us
you've got to get lucky it's kind of you
need it to be punching you in the face
rather than wobbling around to get the
biggest signal you really want to be
lucky and just catch the thing edge on
so you see the biggest signal because
there's a less ambiguity
you you can't tell really directly from
the observation whether you're seeing a
brown dwarf kind of in the plane of the
sky close to the plane in the sky or a
planet close to edge on and because they
had this expectation that they shouldn't
be finding these planets they convinced
themselves that they were seeing a brown
dwarf star binary fairly close on and it
was a bit unlikely because actually it
has to be surprisingly close to face on
for it to work but they sort of convince
themselves they do actually say
somewhere in the paper or it could be a
large planet so they do actually at
least make you know say we might have
found a planet the extra thing that uh
mayor and kayla did is they also looked
at the properties of the star
so they actually could measure
how fast the star is rotating because
you can see one half that if the stars
rotating one half of it's coming towards
you the other half's going away from you
and so you can actually see what you end
up seeing is a kind of a broadening of
the lines so instead of seeing the line
wobbling you see part of the line being
shifted one way part of it the other way
the net effect of that is you see a
slightly broader line so you could
measure the rotation of the star
kind of the the at least but again it's
the same thing like is it a star that's
rotating in the plane of the sky or is
it rotating edge on
but they knew some of the properties of
the star you could just make
observations of it find out what kind of
star it is and we know how fast stars
typically actually rotate that are of
that type
so they have this measurement of
this kind of one component of how fast
the things are rotating and it could be
either a very fast rotating star that's
sort of pole on or it could be a
relatively slowly rotating star that's
age on but we know intrinsically how far
stars like this actually rotate from
that you can figure out that actually
this system is relatively close to edge
on so there's one more leap here which
is that as long as the star's axis of
rotation is the same as the planet's
axis of rotation which for example it is
pretty much in the solar system the
sun's rotating about kind of the same
axis that the solar system is then that
actually tells you that the system has
to be relatively close to edge on
and once you've got that then you know
you've found a planet so that was the
sort of the extra bit that i guess is
what really got them the nobel prize
plus actually just the confidence to say
we found something that no one expected
to find so in the future of one day we
go and visit other systems and other
planets and we can somehow do this
this will be this plant this particular
nobel prize want to be a good one to
visit wouldn't it be like historic one
it'd be like visiting like for humanity
this was a this was a historic site for
us it probably i mean it's not the
easiest one to get to because it is 50
light years away and we know
we now know about planets you know there
are only a few light years away um so
it's probably not the first one that
would ever get visited but yeah when it
becomes routine it will become one of
the stops on the tourist trail i suspect
there's of course there could be other
planets in the system we've just seen
this one
fairly massive jupiter-like planet very
close to the star which really wouldn't
be very hospitable because it's going to
be a gas giant and it's going to be very
hot and very unpleasant
but who knows there could be other
planets further out in the solar system
father of modern cosmology does that
mean there's an older cosmology like
where does it where did where did old
cosmology transition to modern cosmology
i'm giving the transition time around
the 1960s
which by the way is another important
time for the that's the epoch of higgs
and kibble and
brought and angler and people the
discovery of the cosmic microwave
background radiation i think that kind
of transformed the field from being one
that was
full of speculation
and promise in solving einstein's
equations without really knowing what
the background material was in the
universe to first the first time we
established that this radiation this
remnant
of the hot big bang that emerged when
the first atoms were formed say 400 000
years after the big bang and then just
propagated outwards for the next 3.8
billion years that the detection of that
in the 1960s 1965 in fact it was
announced by penzias and wilson
that
where the associated a temperature to
this radiation
that i think is what you might cut i'm
calling here that it's kind of the the
start of modern cosmology and peebles
was there in fact
it's not very well known
but um the paper by penzias and wilson
which is one page long
one
there we are busting a gut writing all
these long
one page paper
about the third or fourth line
having announced that they discovered
this radiation that they don't really
know what it is they say that in the
preceding paper in the journal
which is jim peeble's paper with decay
and roll and wilkinson they say they've
come up with an explanation for what
this could be and it is in fact you know
the microwave background radiation
at a temperature around at the time they
say 3.5 kelvin um
so it's now about scene is about 2.7
kelvin but that's that's okay it was 3.5
plus or minus 0.1 so they were perfectly
okay
but peebles was there and in fact not
only was he there he he he's the one
that actually in the previous paper the
one that literally appears before it
which is a mind blowing four pages long
so that's a huge paper by comparison
he's the one along with
his co-authors who suggest that actually
this
remnant radiation is linked to the hot
big bang and he and that it's got these
thermal properties it's that i think
which is really key that that you can
pin down as being one of people's main
contributions here that he he recognizes
a the significance of the the radiation
has been linked to the early universe
and and the second thing that he does
which i hadn't seen done before he
points out that because we now know the
temperature of that radiation and
because we believe in the idea of
general relativity and we can understand
how that radiation
changes its temperature as the universe
changes scale because it gets redshifted
it cools down as the universe expands it
means it's hotter earlier on and so he's
able to link the temperature you've got
today to an estimate of what the
amount of matter must be in the universe
today because he knows
what it must be sort of in the around
the time of nuclear synthesis he's got a
bound he can use
and and by doing that he actually in
this paper
without i don't think necessarily really
realizing that they're saying there must
be some sort of dark matter he's
actually points out that the estimate
for the amount of baryons matter in the
universe in terms of baryons is actually
lower than the critical matter amount
that you need
that we see today we believe the
universe today is spatially flat that
means there's a critical amount of
matter in there and he said in his
calculations there's not there's not
enough
and if at the end of his first paper the
one that appears with pensions and
wilson comes up with ways of trying to
increase the amount but he was there he
was pointing out this
connection between measurement of the
radiation
and the density of matter in the
universe and that's absolutely integral
to the rest of cosmology in fact the man
in the street
probably hasn't heard of the lambda cdm
model but i think if you said the
standard model of cosmology
that's what you would say peebles
was responsible for the standard model
of cosmology has various contributions
to the overall energy budget
so before peebles was around we knew
that there were baryons right and and
but we didn't necessarily know how many
and people began to put a bound on that
from this paper
but then he made some even bigger
contributions in some sense
the next thing he sort of realized was
that again using the fact that you've
got this cosmic microwave background
that had been detected by penzias and
wilson
he was aware of the fact that there's
fluctuations to be expected in this
cosmic microwave background
and he's the one along with you who who
actually
was the first to fully do sort of
numerical simulations of different types
of cosmology
and predict what these the doppler the
acoustic oscillations were that we see
in the microwave background remember
those peak structures that are big peaks
and then they go down as you as a in the
cmb he was the first to numerically show
what different cosmologies would predict
and so he in in amongst that he showed
what a flat universe would do
and that's the one that pretty much is
observed by first of all by wmap and
then by planck the initial anisotropies
were demonstrated by kobe but the
original work solving the numerical
codes to to show roughly what they would
look like is from peebles what made him
good like why is he why is he good at
this what is it about him that all the
other cosmologists
haven't got i don't think anybody
has his overview
his a is very very strong mathematically
he he's he's developed the statistics
that are you that's used in much of the
analysis of the c and b and of large
scale structure when you're looking at
correlations of different regions of the
sky he developed the techniques you need
more than that and his ability to solve
equations and do integrals and things he
had this he has he's still there he's 85
but he's still very active and really on
the ball he has this overview this he
can see the bigger picture he can see
how a given calculation a given
observation tells you something about
something else in the universe
by extracting out from that small
initial observation that sort of its
impact on the whole of the background
evolution and and to do that is not easy
to because there's so many balls in the
air
and he's able to juggle them all in the
end i think that in many ways is his big
skill have you ever met him oh yeah i've
met him many times at conferences he's
such a nice guy
he's one of these people that
he's
always prepared to give you his time if
you're walking for dinner or having
lunch or
he's
he asks really pertinent questions
and um but he's
i've always found him to be somebody
that is easy to get on with that when he
asks questions he's very polite and but
he's not afraid to tell you if he thinks
you're wrong which he's done to me a
couple of times professor i know in
cosmology there are kind of different
camps and schools of thought you know
people who like string theory and a b
and c and all that is his peoples in in
yours on your side or on the opposite
side
people sit sort of above it all
he i don't think he's worried about the
camps to be honest he's he he goes where
the science tells
really him neil because it's for lithium
batteries
and so he's gone on a battery safari
some of you know that neil is a
motorcyclist he has an electric
motorcycle