about what lies beyond its reach what
lies beyond the tree floor what lies
beyond the entrance of the cave beyond
the next month in the sea the ocean and
eventually the arises what opportunities
are there other safer or better places
to live this family drove us to wonder
what lies beyond the earth itself how
many worlds await us and are they
inhabited I’ve been thrilled by these
questions since childhood when I go
searching for answer I’m an astronomer
slightly planets beyond our solar system
which are called excellence and although
the question about their existence has
been here for thousands of year it’s
only 22 years ago that two researchers
at the University of Geneva building so
they meet in this very contem the first
exoplanets around
like star so it’s a very severe local
story but it has now a worldwide impact
because there is more than 3000
exoplanets that have been detected
sister and there are two main to main
facts that scientists established and
the first one is that planets
ubiquitous know every other star host a
planet 20% of those Falls at least the
planet that is the size of the earth now
there is a hundred billion storing our
galaxy so that will make for 20 billion
earth-sized planets it’s mesmerizing
but the second fact is to me even more
striking and the fact that there is a
fantastic diversity among the planet
discovered it’s beyond imagination but
it’s actually my job to try and imagine
it and it’s very important this
diversity because how a planet looks
like today is how it formed and if you
are able to understand processes at the
origin of all the planets we know that
it means that we can explain how our
planets form and how life eventually
appear and so these these two facts
raises raise two fundamental questions
if life arose under from there are
billions of is life a common phenomenon
in the universe and however if there is
a huge diversity in life is able to
blossom in very dire
very different from our environment
would we even be able to proceed to
recognize it so I need to make a
simplification here when we talk about
life
I will speak mainly about microbial life
which my father mean it’s the biomass of
the earth
this beautiful organism that you see
here is the reason of your presence in
this room it’s the first organism this
is GMO bacteria in all of photosynthesis
so it’s at the origin it’s ancestor are
the origin of the of the oxygen we are
breathing so it literally 2 and 1/2
billion years ago fill the primordial
and posture of the earth with oxygen so
it completely changed the atmosphere of
the earth and it’s the very reason why
my colleagues and I are looking trying
to look at atmospheres of exoplanets to
try and detect such big changes to
existence of oxygen that could be linked
with microorganism living at the surface
of the planet but in order to try this
microorganism needs to make ingredients
that are united on this country on this
beautiful picture liquid water at the
surface and sunlight and these two other
of these two things are comes together
in only one place in our solar system
it’s the earth now there are all the
places in the star system that looks
like a list and one of the most striking
example is this one so this is the green
of the same sunlight on the sea at the
surface of Titan which is Saturn’s
because the only thing here is that
Titan is very far from the Sun
suppose it’s minus a hundred and eighty
degrees Celsius so it’s low liquid water
that you see it’s a lake of liquid
methane that is actually laying onto the
bed of rocks Lee’s water ice now below
this ice shell that could be some water
ocean one side down on other moons of of
giant planets which are all very cold
the only thing is that some I cannot
reach these places directed and besides
this the solar system we need to very
friendly condition for life to blossom
so what we do is that I will show you
how the the Sun of the temple extent the
fruit of a bunch of the thousands of
exoplanet we have detected having no
places like you have in the solar system
makes it really critical to determine if
there is some cedar places elsewhere
around other stars so I will solve the
planets by their temperature and density
and I will make a pure now 500 of
exoplanets for which we know the masses
the spices hence there
and there are distances to the song so
we can assess their approximate surface
temperature everything you see beyond
that in this picture like overall
stripes we it’s fantasy it’s an art
especially just do not know and to me
this is really fascinating because it is
lots of room for imagination so playing
with the laws of physics chemistry and
climate sciences we use that as its
angles I’m trying to make prediction
that we try to verify and for instance
it would be extremely tempting to apply
a hockey planets that are about the size
of the earth in the window in the
Wrights temperature range so that liquid
water could answer their stories on into
their atmosphere
it’s an unfortunate coincidence that
these planets are precisely the one that
are the most difficult to detect and the
most difficult to characterize it’s much
easier to characterize the atmosphere of
giant hot giant gaseous planets and
while it seems a tad frustrating at
first the left field extraordinary
findings that teachers about candidate
are more logical
so I would like to share with you know
one of these this example it’s maybe the
most exciting discovery I made in my in
my career and it’s about a planet that
is about the size of Neptune Neptune is
up there in the cold part of this
diagram and planet that is emphasized
here is 4 GJ 4 3 6 and that exchange in
spite of being mainly composed of of gas
don’t squash one question even
temperature
that should call these planets gas giant
so by golden baby urchins by lack
of more adapted terminology and it helps
because it’s very close to its stuff so
let me try to give you the feeling of
how close it is in our solar system
mercury is the closest planet to the Sun
its orbit around the Sun in just 88 days
that’s just one year from you if I take
the system of GJ 4 3 6 9 instead of the
Sun this is what they thought it would
look like a star in just three days okay
every three minutes surfaces extreme
environment in terms of standard
recognition fortunately for us the star
is much smaller and colder and rather
than at the Sun and that it’s easier to
observe the atmosphere of the planet and
the key thing here that makes it
possible is the fact that as seen from
the earth the planet is impassive in
front of the star we call these
transients where the planet from the
rocks a tiny bit of the fraction of the
Starlight and when it has an atmosphere
and even tying a fraction is actually
filters actually the Starlight and if
you are able to to analyze the line that
has filters who these are consumed with
the instrument go spectrograph we can
retrieve the composition of the
planetary atmosphere the only thing is
that it’s really challenging because I
as you can see I really are cooled by
the atmosphere or other surface of the
star is very small so it’s very small
signatures so by I do to God
sure was try to get to detect the
lightest possible species in the
atmosphere because it would then be the
top of the items you may recover a
bigger fraction of the surface of the
stomach in the single peak is mostly
composed by hydrogen which is precisely
the lightest gas in the universe so I
thought okay let’s propose to observe to
detect hydrogen in this in this sense
and the observation were only possible
with the help of the Hubble Space
Telescope which is a very competitive
instrument if you want to basically all
astronomers to observe with it because
it’s a kind of our choice so there’s a
lot of demand actually took me four
years to convince my peers in the
selection committee of the observing
programs there that it was worthwhile to
do this this observation but when after
after several years I can to be obtained
all of my data so 2014 I was run against
because what I saw on that I’m going to
show to show to you it’s just something
that nobody was prepared but you see
here and I know it doesn’t look very
impressive and it’s so because it’s all
data from Hubble so you could see
looking at the detector offer virtually
putting your eyelids so it looks all
dirty because it’s it’s not been
properly accused in fact in age of the
staff who spectrograph what they of the
shape will the interesting thing is to
compare what the data
obtained with the Kinect is now in front
of the star to the data set of penguin
and he’s in front of the star and the
sharper eyes the moon you might have
noticed the decrease of the of the
Starlight in the vehicle region here and
the fact that we can see that it is
absolutely extraordinary means that the
signal is huge which in that’s the
atmosphere of the planet it must be huge
in front of the star how huge this is
what my team and I try to determine with
numerical simulation and we found out
that the atmosphere of this planet
associated with child commits cloud of
hydrogen which was completely a complete
surprise and what is happening to this
to these subjects that is so close we
saw that the planet is losing its
atmosphere to space the star strips the
planet out of its atmosphere slowly and
others there are still gaps around it
but the thing that is Rhema summarizing
is when you consider that there are
planets out there that this one but
close to their star and actually this
atmospheric evaporation would explain
existence of a population hot very hot
very close to the star rocky planets
that doesn’t exist in the solar system
and this path of formation of rocky
planet physically evaporates a planet
with orgasm you leave only the rocky
core it’s something that never happened
around the Sun and it’s very interesting
to consider why around there are
basically because the giant planet
Jupiter Saturn did not migrate in more
close to the Sun and that’s very
fortunate for us because studies shows
that if Jupiter had migrated in while
very close to the Sun you could have
ejected all the small planets on its
path including earth so we wouldn’t
either
Jupiter are migrating so looking at
these system review how kind of fragile
we are in a way now let’s finish by
getting back to birth and so you might
folders okay this is all well a nice but
how do we characterize the difference
here of a place where we know there is
there could be life but could we detect
oxygen and water in this atmosphere so
either good or the bad news the good
news is that you can apply exactly the
same technique I just explained to you
the bad news is that Hubble is much too
small to detect something you see the
limp of the atmosphere of the earth it
carries a 2.5 Muir diameter of newer
space the cyber school bus but it’s much
too small and actually my first job as a
PhD students 13 years ago was to
determine to calibrate how big a
telescope should be to be able to detect
this atmosphere of a nose like Venice
the answer is well brutal is 40 meter
telescope in space in the description
below but activity dimensional 400
windows you have to find the good
planets that you want to characterize
and then there is a very because
getting such furniture even they have
already and especially in Switzerland we
are really under the bridge
we have conceived what is now considered
the most the bests planet-hunting device
the hospital graph which is installed in
a telescope in Chile last month the
say-so of this instrument Chinese
spectrograph called espresso that we
and the mass of appendix that is like
now to get the density of such a planet
we need also to measure size unfold it
we will bring Switzerland beyond before
we will switch them to space by building
the first tree-sweet slit space mission
which is specialist of cool chaos and
it’s much smaller than half of it it
will be very sensitive and very precise
with the size of exoplanets and it
involves a lot of institutions with say
London in Europe the instrument has been
bill it’s already in Paris what you see
at the top of the screen and later I
could be launched to leave any for
launch at the end of next year and the
data will arrive in so heavenly UNESCO
in this very contem so
we are ready to find the right planets
but no no I just said if you slide ago
well you need an extremely large
telescope to characterize a certain
sphere so remember from the introduction
is old 7 as an S and you might see
there’s a hole that leads to the Sun its
Atacama Desert which coincidentally is
the best place in the world for us a
little observation this summit has been
engineered it has been flattened to
prepare for the construction of the
biggest telescope ever built
it’s cold then you guess the extremely
large telescope
the size of its mio is 40 meters so we
have never been that close of being able
to detect life elsewhere and I think
this huge beam of makes a good
conclusion for this store because it
actually you know is something in which
which reflects new image and the maybe
the most beautiful I hear in all of this
is that searching for life elsewhere
with Zika teaches about ourselves
thank you very much [Applause]