the earth is not alone in the last few
years scientists have found that our
planet is just one of billions out there
in the Milky Way galaxy
there's a really decent chance that
there are more planets in the galaxy
than there actually are stars
we're now scouring these planets for
evidence of atmospheres liquid water and
life itself
we are going to know where in the night
sky
you can point and find another earth we
have a scientific method to actually
determine whether there is life on
another planet another earth alien life
the truth is out there but are we ready
for it
the earth gives us the blueprint for
life as we know it the Sun warms our
oceans creating the perfect environment
for all scales of life from the very
smallest to the Giants that eat them
Mountains Plains and forests teen with
plant and animal species and it's all
cocooned in a thick atmosphere that
nurtures and protects for us it's
paradise twenty years ago
a group of scientists decided to find
out if there were other paradises out
there so-called exoplanets orbiting the
stars that light up our night sky just
in the last decade we've had this
expl*si*n and the discovery of these
exoplanets which has revolutionized the
whole field of astronomy
the early days of exoplanet hunting
turned up enormous jupiter-sized planets
by the boatload
these hot gas each iins proved easy to
find but hostile to life as we know it
now though new telescopes and
technologies have allowed astronomers to
target smaller planets earth-sized ones
and the stunning results have
transformed the way we see our place in
the universe
we now know something precious that our
planet Earth is not unique it's not even
rare there are tons hoards flocks if you
will of other earth-like planets out
there fluttering around the other stars
some stars probably have multiple earths
orbiting them that's how common
earth-like planets are
we owe this exoplanet expl*si*n to a
Space Telescope called Kepler the Kepler
space telescope is an observatory in
space that is staring at one spot in the
sky it's looking at roughly 150,000
stars and it's looking for the tell-tale
sign of planets orbiting those stars
then every time the planet passes in
front of the star it'll block a little
bit of that star light and if you plot
the amount of light you get from the
star it drops and then goes back up as
the planet passes in just four years
scientists have detected over a thousand
exoplanets just from their shadows
but Kepler has a problem it can't tell
if the shadow is made by a giant gassy
planet hostile to life or a potentially
habitable earth-like planet
what we're measuring when a when a
planet passes in front of its host star
is what is the area of the planet
relative to the area of the star that
it's passing in front of it's a it's a
ratio basically but Jupiter sized
planets crossing giant stars full Kepler
because they block the same fraction of
light as earth sized planets crossing
smaller stars to prove a planet is earth
sized you first need to measure the size
of its star using the world's biggest
telescopes but that's time-consuming
expensive and it creates a huge
exoplanet backlog but astronomer Kavon
Stassen has come up with an ingenious
shortcut by turning the raw Kepler data
into sound what the Kepler telescope
directly measures and the data that we
use is small changes in brightness that
a star produces due to the flickering
arising from the boiling and roiling
motions of gas at its surface what we
can do then is take that light
flickering data and transform it in a
sound studio for example into audio
frequencies and so then we can represent
with sound what we're actually detecting
with light
the bigger the star the more its surface
boils with activity making big stars
flicker more powerfully converted to
sound this boiling becomes a deafening
hiss well let's listen to some stars
okay can we hear the red giant star
please I'm gonna bring up the volume
here
this is a very large star very low
density and so that large amount of hiss
is the result of vigorous boiling and
churning at the surface of this large
red giant star can we get the dwarf star
please on smaller stars sunspots
dominate the sound profile creating a
low-frequency drone
actually sounds like a series of clicks
come but below the clicks lies the faint
hiss Kavon needs to size the star
underneath it at a very low level is a
little bit of hiss
that little bit of is actually the light
flickering that we're interested in by
accurately measuring the level of this
background hiss Kavon can work out the
size of the star in this case it's
around the same size as our star the Sun
cave-ins work could be the breakthrough
exoplanet hunters have been hoping for
it's cheap the results are practically
instantaneous and once you know the size
of the star figuring out the size of the
planets casting shadows over it is
child's play
it feels like a very privileged time to
be a scientist to be an astronomer
working in this area and contributing to
the hunt for the next earth here we are
actually discovering these worlds by the
hundreds and now on the cusp of being
able to identify the next earth
astronomers suspect there could be tens
of billions of rocky earth-like planets
in the Milky Way places where perhaps
life has gotten a foothold
but life as we know it requires water
how can scientists possibly find this
miracle substance on planets light-years
away water divides our living world
those with it prosper
those about suffer remarkably the water
we drink today contains the same atoms
as the water dinosaurs drank 100 million
years ago it's the same water that
formed clouds of the earlier four
billion years ago and every organism
that has ever existed on earth has used
this single ration of water as the
biochemical powerhouse that keeps it
alive
on earth all life requires liquid water
to grow and reproduce it's the common
ecological requirement for life liquid
water is just so good for getting
evolution going molecules can dissolve
in the water actually interact with each
other for more complex chains it does it
with charge there's positive charges and
negative charges separated between the
hydrogen and the oxygen in h2o those
charges break apart the hydrocarbons the
carbon-based molecules that persist
everywhere in nature
now that's very rare hardly any other
liquids do that so liquid water is a
natural starting place when you look out
into the universe and say what planets
could possibly have life
to understand how much liquid water is
out there astronomers must first
calculate how common water is in all its
forms
amazingly they find it everywhere they
look water is incredibly common in its
gaseous form we see water vapor filling
the space between the stars we see it in
clouds of material that are actually
forming new stars and planets right now
since water is a fundamental building
block of stars and planets exoplanet
worlds must surely have it in abundance
but if you're looking for life you need
to find liquid water and plenty up to
find it
astronomers take their cue from a fairy
tale
everybody knows the famous story of
Goldilocks and the three bears and the
the cup of para girar one was too hot
one was too cold I was just right when
it comes to cooking up life like a
porridge you need to have an environment
that's not too hot not too cold just
right and traditionally we look for that
at a certain distance around a star at
first astronomers based this magical
distance known as the Goldilocks zone on
the Earth's orbit around the Sun but as
they found more and more exoplanets
they've had to re-evaluate the
boundaries for liquid water there isn't
a single distance it depends on the
brightness of your parent star a dim
star you need to be closer a hot star
very bright need to be farther away
scientists have calculated just how many
rocky planets may lie within the
Goldilocks zone of their stars
it comes out to over 30 billion
potentially watering worries even more
remarkably recent discoveries have shown
us it's not just planets that can bask
in the warmth of the Goldilocks zone
there may be moons paint blue with
oceans - most of the planets were
finding our big jupiter-sized planet
however a lot of them were are orbiting
roughly where the earth is orbiting the
Sun so even if the planet that we're
finding can't support life it could have
a moon a moon with an atmosphere that
could support life
and the biggest of these rocky moons may
resemble our home there could be
billions upon billions of XA means out
there and even perhaps countless
paradises teeming with life
David kipping searches for exomoons by
looking for double dips in the
brightness of distant stars we look for
XA means in a very similar way to the
way that we look for planets by looking
for them transit the host star
now if that planet had a moon then we
should expect to have one big dip due to
the planet and then one smaller depth
either to the left or to the right due
to the new
habitable exomoons may play host to one
of the most spectacular sights in the
universe
imagine a warm rocky world just like our
own with oceans mountains but in the sky
a massive ringed planet with a fiery
sister moon sh**ting hot magma into
space
exoplanets and now the vast potential of
exomoons int a galaxy filled with the
possibilities for life but a rocky
surface and liquid oceans may not be
enough
biology needs the breath of life air
backlit by the Sun a halo appears around
the earth a pale blue ring of light our
atmosphere and we owe it everything the
Earth's atmosphere provides the gases
that fuel the biochemistry of advanced
life but it also protects the oceans
from the full fury of the sun's rays
preventing the water from boiling away
into space without an atmosphere there
would be no wind no rain no fresh water
and probably no life atmospheres are
absolutely essential for life take a
look at the planet Earth and you realize
that just like the skin of the Apple the
skin of the apple preserves the Apple
well the atmosphere of our planet
preserves the oceans and makes possible
the presence of life as we know it
scientists in search of living
exoplanets hope to detect the thin gassy
envelope that should surround these
alien worlds to do it they're turning to
the power of rainbows in the same way
that water splits sunlight into a
rainbow astronomers use instruments to
split starlight into a band of colors
called a spectrum
it's one of the oldest tricks and
science
and one of the most revealing several
hundred years ago scientists first began
to take something like a prism and put
it in front of their telescope so he
started taking the light from stars like
the Sun and actually spreading it out
into a spectrum and what they saw was
kind of surprising so instead of seeing
a rain continuous rainbow of light they
saw that rainbow but they saw these dark
lines superimposed on top
each chemical elements of the star's
atmosphere absorbs different parts of
the spectrum creating signature dark
bands for instance up the top there's a
pair of lines in the yellow part of the
spectrum which are due to sodium like a
DNA profile for stars spectral analysis
has taught us almost everything we know
about stars today but these same lines
may hide a marvelous secret the faint
signal of alien atmospheres and perhaps
also alien life so the challenge is that
these planets are very small and very
faint so we can't actually go and
directly measure the light emitted from
the planet the same way that you go and
measure this lovely spectrum for the Sun
instead we have to rely on more indirect
methods so one indirect way of doing
that is to wait until the planet passes
in front of the star when the light of a
star passes through an EXO atmosphere
the gases that surround the planet
should stamp their own faint lines on
the star's spectrum so as we watch the
light from the stars transmitted through
that atmosphere its
atmosphere is going to act like a little
filter so a part of the star light is
going to pass through that atmosphere
and we're gonna see that in printing
extra lines on it which are due to the
planet's atmosphere so that change in
the spectrum tells us something about
the properties of the planet's
atmosphere
the one chemical astronomers most want
to find is oxygen because only life can
produce enough oxygen to be easily
detected it's a so-called bio signature
the race is now on to find bio
signatures in the atmospheres of rocky
exoplanets and while some groups look
for rainbows indirectly others are
tackling the challenge head-on 29 all
right we're off
then Oppenheimer is part of a team
trying to take direct photographs of
exoplanets using massive ground-based
telescopes
we're within minutes of taking our first
long exposure and I hope it's good the
greatest challenge to imaging exoplanets
is the blinding light of the parent star
which shines tens of millions of times
brighter than the planet itself
the trick is to stop the light of the
star from entering the telescope sensors
by blocking it using a series of masks
and lenses called a coronagraph right
now we're standing right underneath the
telescope's primary mirror and the light
comes through a hole in the middle of
the mirror and goes into this crazy box
here which is full of optics motors
sensors and electronics that all allow
us to precisely control the star light
that's coming through the system using
state-of-the-art software they
manipulate the coronagraph to black out
the unwanted light under good conditions
we can actually carve dark holes into
this image of the star so that we can
see really faint things in those regions
coronagraphs present an intriguing
problem though errors within the optics
produce tiny flares of starlight called
speckles that look just like exoplanets
but man has come up with an ingenious
way to tell speckles from planets so
we've developed a technique where we
exploit an aspect of speckles which is
that they change position in the image
depending on what color you take your
image at so Ben takes the same image of
the star through different color filters
and runs them like a movie the speckles
appear to move across the screen but the
planets stay stuck still allowing Ben to
easily pick them out and so I'd like to
point out that there is a little thing
right here that if you watch for you're
careful you'll notice that it doesn't
move and the speckles are washing over
it
this stationary blob is a candidate
exoplanet and below it and to the left
is a second they both appear to orbit a
star around 200 light-years from the
earth just a decade ago capturing an
image like this through a telescope was
unthinkable but today thanks to the
ingenuity of astronomers like Ben we
have hundreds
and by analyzing the light for these
distant worlds scientists can work out
their chemical composition
and potentially the fingerprints of life
at this point we're studying much larger
planets gaseous things like Jupiter that
most likely don't have any kind of life
like we know it but that's a first step
and we're going to fainter and smaller
and smaller planets as time goes on as
we develop this technology in the
not-too-distant future scientists may be
able to simply scan a star for
earth-like planets and find the
signature of life there we can look
right at the light from a little planet
around its distant star and that opens
up a whole range of possibilities for us
to not just detect the planet but to
starting the planet I mean this all
sounds like science fiction but there is
a reality to this we have a scientific
method to actually determine whether
there is life on another planet life is
one thing intelligent life another all
together that requires billions of years
and a powerful force field like the one
we owe our lives to every day
if an alien astronomer were to file a
report on our home solar system they
might make a surprising observation
because of all the eight planets that
orbit the Sun they could easily conclude
the two not one were suitable for life
it's an easy mistake to make because the
Sun has two planets within its
Goldilocks zone
the Earth and Mars
both planets have surfaces warm enough
for liquid water to pool on but while
the earth is blessed with warm liquid
oceans Mars is dry and dead
the one crucial difference between these
two planets could be the key to finding
truly habitable exoplanets a magnetic
shield our Sun is constantly hurling
deadly radiation out towards us only our
magnetic shield the magnetosphere saves
us without it the solar wind would blow
our atmosphere away and without an
atmosphere liquid water could not exist
on the surface in order to have liquid
water not only do you need the right
temperature but you need the right
pressure you know if there were no
atmosphere here right now even at the
same temperature we are today all of the
water would boil off into vapor
immediately so where does the Earth's
magnetosphere come from and why does it
Mars have one actually in the past both
Earth and Mars had magnetospheres but
Mars lost its around 4 billion years ago
and with it the potential for life
both the earth and Mars were born into a
realm of v*olence asteroids smashed into
their surfaces turning rock and metal
into a molten mass
as they started to cool a solid crust
formed on surface but the molten metal
below churned as the planets turn
inducing a magnetic field which rose
high up above the surface of both
planets at the same time active
volcanoes pumped gas into the space
around each planet protected by the
newly formed magnetic field these gases
built up into thick atmospheres creating
the air pressure for liquid water to run
on the surface for over a hundred
million years both Mars and Earth for
warm wet paradises primed for life to
take off then quite suddenly
Mars's magnetic protection disappeared
the solar wind blew its atmosphere into
space and its oceans boiled away leaving
the dry sterile red rock we see today
Mars is fundamental problem is is that
it's smaller than Earth and because it's
smaller the internal core of Mars cooled
down and solidified and once it becomes
a solid metal there's no more magnetic
field magnetic field shuts off
essentially and the atmosphere therefore
is vulnerable to both energy and
radiation from the Sun and the rest of
the galaxy and probably just blew off
whatever life was on there at least on
the surface is now completely exposed
all rocky planets will one day lose
their magnetospheres as their cores cool
and turn solid so to know if an
exoplanet is alive you need to work out
if its magnetosphere is still active but
magnetospheres are tough to measure
because they are unbelievably weak the
earth has a magnetic field of
approximately half a Gauss which when
you think about it is actually really
weak our fridge magnets are about a
hundred Gauss they're much stronger
Excel planets are too far away for us to
measure such weak magnetic fields
directly but there is an indirect method
when electrons in the solar wind
interacts with a planet's magnetosphere
they emit radio waves that beam out into
space turning the planet into a giant
radio beacon
astronomers like of geniu hoped to use
these signals to spot habitable
exoplanets not only that the frequency
of the signal should also tell her how
big the planet is if we're looking for
the magnetic signature in the radio
waves of a giant planet say a hot
Jupiter we expected to have a strong
magnetic field and therefore would have
a high frequency and around 100
megahertz kind of where the limit of
this radio is however a weaker field
like Earth's requires us to go down to
lower and lower frequencies so instead
of a hundred megahertz we go down to ten
megahertz but hunting for exoplanets at
ten megahertz presents a unique
challenge
because the Earth's own magnetic sphere
creates a deafening radio roar at that
frequency so define alien Earth's using
radio requires a dish in space when we
want to look for magneto spheres of
extrasolar planets we really need to get
outside of the earth-moon system in
order to get away from all the radio
frequencies that are bouncing around the
earth
with a slew of new technologies and
upcoming technologies scientists are
edging ever closer to the ultimate prize
finding a second earth
I wouldn't be surprised if we have that
data about an earth and about life on it
around another star in 10 or 15 years
I'm hoping to see that soon
using shadows rainbows and now radio we
finally have the tools to detect a
planet just like our own
but in the rush to find the Earth's
identical twin are we missing something
big
what if earth is an outlier a freakishly
lucky place on the very fringes of
habitability could there be another kind
of planet out there even better for life
for years astronomers have scanned the
heavens for planets that could sustain
life they faced their search on the
earth seeking the exact same conditions
an exact same size I think right now
there is a huge focus to finding
earth-like planets now whether or not
there actually is life there that is
another question altogether but after 20
years of searching for an earth clone
the exoplanet hunters may be about to
switch targets recent observations have
revealed a brand new class of planet
it's one that may eclipse our own home
we've learned something in the last few
years that really shocked us with the
Kepler space p*rn telescope we have
found hordes of planets that are a
little bigger than the earth we never
imagined that there would be such
planets in fact in our own solar system
there are no planets between the size of
the earth and the next largest planet
that of Uranus and Neptune astronomers
call these mysterious planets super
Earths
super earths are about three to five
times the mass of the earth and there's
nothing like that here we don't know
what they're like it's an entirely alien
sort of planet in just the last few
years astronomers have begun to imagine
the conditions on this new class of
planet and they've come to a startling
conclusion super earths could be super
habitable
there are probably planets out there
that are even more hospitable for life
planets that have even more chemicals
necessary to create the organic
materials that create life conditions
that make it more likely to get life off
the ground
imagine a rocky planet twice the size of
the earth
dramatic volcanism on the surface
betrays a vast heart of fire that beats
within its core
we expect that a heavier earth will be
more geologically active that the
increased amount of geothermal heat
within the super earth will lead to
stronger motions of the magma underneath
the crust
belching volcanoes dot the surface of
this super earth
their gases feed a super thick
atmosphere and help to regulate a super
stable climate many times life on Earth
was nearly extinguished for example once
upon a time the earth was snowball earth
completely covered in ice maybe in these
other planets there are earth in which
snowball earth never happened that the
taught climate was always stable and
temperate the grip of gravity is three
times stronger here than we're used to
it pulls mountain ranges down to a third
the height they'd be on earth
gravity also flattens the ocean bed
making shallower CDs filled with
volcanic island chains and the
nutrient-rich waters that surround these
archipelagos provide the perfect
conditions for life
in these other planets perhaps they have
conditions which would make DNA get off
the ground much earlier and flourish
much more quickly
finally our super earth may be protected
by a super magnetosphere the magnetic
field strength is a condition both of
the mass of the planet as well as its
rotation speed and so it is quite likely
that a planet that is a couple of times
bigger than the earths would be able to
develop a stronger magnetic field may
shield the planet even better than our
magnetic field shields us having a
stronger magnetosphere would be a
distinct advantage for life on a super
earth surrounding the Milky Way's most
plentiful kind of star the M dwarf or
red dwarf star red dwarf habitable zones
are much closer in than the earth is to
the Sun because their host star is so
dim as if you took the terrestrial
planets in our own solar system and
zapped it with a shrink ray g*n and
shrunk them down to orbital periods that
are less than about 30 days meaning that
they're very close to their stars some
astronomers believe these planets are at
risk from solar activity such as deadly
flares
but a super-earth with a super
protective magnetosphere may well resist
these deadly rays allowing life to
flourish under a psychedelic sky full of
swirling Aurora's if one was standing on
a super earth we would see the aurora
come down to lower latitudes might get
different colors
if I had the opportunity to travel to
one of these exoplanets I would snap
that up pretty quickly most intriguing
of all if life does exist on a red dwarf
super earth it could be home to the
longest-lived civilizations in the
entire universe the advantage of the M
Dwarfs is that they last for much longer
and if you had a super earth then
keeping a strong magnetic field going
for billions and billions of years
especially now around a red dwarf that
is going to exist for billions and
billions of years you might be in that
perfect system where life can exist and
evolve into even more complex beings
than us
we're getting so close
our local neighborhood of stars teens
with red dwarfs bursting with the
potential for advanced life
but they're also cosmic K*llers out
there lurking in our galaxy prime to
wipe out life on a regular basis
is anywhere safe the exoplanet
revolution is in full swing the Kepler
space telescope has scanned our local
neighborhood of stars for planets and
it's found them by the thousands
for a long time we didn't know if the
other stars in our galaxy had planets
and for thousands of years there was no
way to answer that question finally now
with modern technology we can do that
and to our surprise we found they are
extremely common from Kepler's small
sample astronomers believe there could
be tens of billions of rocky earth-like
planets throughout the Milky Way where
life may already be thriving but how
many of these countless worlds is held
onto this life long enough for
intelligence to evolve
the answer surprisingly may depend on a
planet's galactic zip code
the universe is not a happy safe place
the universe wants to k*ll us
it's incredibly violent out there
they're solar flares and supernovae and
black holes and colliding galaxies and
all these really amazingly dangerous and
violent events it's actually kind of
amazing that we're here at all
in order to develop advanced intelligent
life an exoplanet
may have to avoid these cosmic K*llers
for over three billion years if we look
at the history of the earth the first
thing that happens that's important is
the origin of life right away very
quickly but then nothing for a long time
you have nothing but microbes stomping
on the earth
for the first two and a half billion
years the earth was ruled by
single-celled Goom multicellular life
has only been around for a billion years
fish for 500 million mammals for 200
million
and modern humans have only walked the
earth for the last 200,000 years
the lesson is clear it takes a long time
to cook up intelligent life
but most planets in the Milky Way don't
have that kind of time
astronomers believe that a planet's
position within a galaxy may determine
if it gets hit by global extinction
events there's an idea of a habitable
zone for a galaxy and it's an analogy to
the habitable zone around stars stars
too close to the galactic center are in
the f*ring line from their violent
neighbors which frequently blast them
with deadly high-energy radiation
in the middle of a galaxy we have a lot
of bright stars and young stars and
maybe even supernova going off and so
there's a very harsh radiation field
that's not good for life fired up by the
supermassive black hole that sits at the
center of the Milky Way
this cosmic Killzone stretches out
around 8,000 light years from the
galactic center and extends out along
the densely packed spiral arms any
planets that exist within this zone are
likely to have their surfaces regularly
scrubbed clean of life fortunately for
us our home star the Sun sits in a
relatively empty quiet zone between two
of the galaxy's spiral arms so there's
this idea that there's a band in the
middle of the galaxy that's the Galactic
habitable zone where you don't have too
many stars going off you don't have too
many supernovae so it's quiet in that
way those might be great places for
complex life
these green zones are like the suburbs
the Milky Way galaxy they're sheltered
from the worst of the galaxy's radiation
it's here that earth-like worlds will
have the luxury of long uninterrupted
periods for life to take hold and
develop into more complex forms and
eventually perhaps intelligent life like
us
the Galactic habitable zone is no more
than a fledgling theory but if it's true
it reduces the number of places where
advanced life could flourish in the
Milky Way
the good news is those places should be
near us and aliens more likely to be on
our doorstep and with our technology
getting better every day it surely won't
be long before we find them
I think in 20 years time I'm gonna be
able to look up into the night sky and
say there really is another place I
could stand like this and feel at home
suddenly we humans will realize for the
first time that there are other cultures
other civilizations probably other
religions out there among the stars and
we are just one member of a grand
galactic tribe to have cousins that we
one day may communicate with seems to me
to be potentially one of the greatest
developments that humanity will ever
ever experience and if that isn't worth
doing I don't know what is
03x09 - The Search for a Second Earth
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Science documentary television series that provides scientific explanations about the inner workings of the universe and everything it encompasses.
Science documentary television series that provides scientific explanations about the inner workings of the universe and everything it encompasses.