Kind: captions
Language: en
aliens
extraterrestrials celestial beings
call them what you will we spent a lot
of time here on earth preparing for
contact with some sort of intergalactic
creature
[Music]
perhaps a nice one like e.t
he's a man from outer space and we're
taking him to a spaceship or perhaps a
bad encounter as in war of the worlds
what's that
the flame springs in the mirror that
leaps right at the advancing men
strike some head-on
lords are turning into flames
there's no shortage of artistic
interpretations of aliens but far far
away from the bright lights of hollywood
a lot of questions remain such as
what might extraterrestrial life
actually look like
what would we have in common would we
recognize some piece of ourselves in
them
and what would actually be alien to us
earthlings accustomed to carbon-based
water loving life
and cards on the table how likely are we
really to make contact
odds are earth probably doesn't host the
only life in the universe but if we ever
do find it it'll probably look like
well why don't we find out
today on nova now universe revealed the
search for alien life in our galaxy for
anyone or anything listening out there
i'm your friendly podcast hosting
earthling alok patel
[Music]
when you think about the word for alien
we think about extraterrestrial so okay
we gotta find a terrestrial world but in
chinese right i'm half chinese
the word for alien in chinese is why
shinrin which is other star person
so i think in chinese they're already
ready for us to find life on an
exoplanet because we gotta go to another
star which is pretty cool
anjali tripathi is an astrophysicist at
nasa's jet propulsion laboratory and the
science ambassador for nasa's exoplanet
exploration program in other words she
searches the galaxy to discover
exoplanets that is planets outside of
our solar system
i tell people my job is sort of like
being where's waldo but on an
astronomical scale
in the last few decades astronomers have
discovered thousands of exoplanets
revolving around stars in our galaxy so
it's amazing to me that within my
lifetime we've discovered all of these
exoplanets because i remember being a
kid there were nine planets and then we
lost one poor pluto and then the number
just kept growing
though there's some dispute over when
the first exoplanet was found there were
definitely some important discoveries
made in the
1990s in 1992 there were these polish
astronomers who were looking at
millisecond pulsars they've got these
beams of light coming out of them that
they're spinning really fast so that's
that millisecond thing that each second
it's gone around like a hundred times to
understand the pulsar timing method
picture a lighthouse with its light beam
revolving at regularly timed intervals
scientists can measure the timing of
pulsars so if they detect that the
rotating light beam is a little early or
a little late that could be due to a
planet's gravitational pull
suggesting there might be a planet
orbiting that neutron star
and so it was from observing these
pulsars and noticing the timing was off
that these astronomers discovered that
there were a couple of planets actually
orbiting these dead dying stars but in
exoplanet astronomy we often also talk
about 1995 as being this big turning
point because that's when we started
finding planets that were big puffy
jupiter-like planets and they were
actually found around stars that are
like our own sun so rather than a dying
star these are solar type stars and so
that was the sort of beginning of the
era of exoplanet astronomy
could you walk us through the methods
that are used to discover these
exoplanets and how do they work
so the way that 51 pegasi in 1995 was
discovered that first planet was
discovered using what's known as the
radial velocity or doppler method and
that's the fact that a planet and its
star that it's circling or stars are in
a little bit of a dance kind of like you
could imagine that star is wearing a
hula hoop and in order to keep that hula
hoop going you've got to wiggle your
hips and so that star is going to move
back and forth and that's actually
something that we can track the motion
of that star's light here on earth
so as a planet travels around a star
making it wobble back and forth the
wavelengths of the starlight get
alternately squeezed and stretched as
the star moves slightly closer or
farther from us respectively
similarly if you've got just the right
angle that you're looking at the star
and planet you can actually see the
planet or planets crossing in front of
the starlight blocking it out a little
bit so you've got your starlight
blinking at you dimming the light
repeatedly and if we can see that
happening regularly enough
we say hey there might be a planet and
so that's a really popular method called
the transit method there are other
methods that we're using to find planets
but they haven't yet found as many in
large part due to technology limitations
so far we've found a majority of the
exoplanets using the transit and the
radial velocity methods but in the
future scientists hope to capture direct
images of exoplanets say cheese you sexy
exoplanet
so this is where you actually see the
planet which is the thing that you most
want to see because you're finding it
directly but you actually can't do this
in a lot of cases right now because it's
like trying to look at you know a fly
next to
a lamppost right the light is so
blinding it's really hard to see unless
that's really far away from the star but
with the coming technologies and
upgrades in instrumentation we're really
hoping that we can then be able to block
out the starlight and see planets
closing so that you can find these
worlds that are just as exciting as with
the other techniques but we can see the
planet
astronomers have been able to detect
exoplanets from here on earth but the
number of known exoplanets exploded when
nasa launched its kepler spacecraft in
2009 three
two engine start
one zero and liftoff of the delta ii
rocket with kepler on a search for
planets in some way like our own
chamber
it would not be an overstatement to say
it revolutionized the field of
exoplanets because just staring at this
one patch of the sky it found thousands
of exoplanets
and when it found so many exoplanets
right you know we were in the tens
hundreds of exoplanets before kepler
not only did it find a huge number but
it found an incredible diversity or
menagerie of planets because we found
planets of all different sizes we found
that they had all kinds of different
properties from anything that we had
seen thus far and so kepler really
opened our eyes to what else could be
out there that we just are starting to
scratch the surface of the kepler space
telescope relied on the transit method
to find exoplanets since 2018 it's been
remaining in quiet orbit around the sun
far from earth enjoying its happy
retirement
so that's kepler can you tell us about
tess the transiting exoplanet survey
satellite mission
tess is the follow up or test is the
successor to kepler
it is still operating at this very
moment unlike kepler which stared at one
little patch of the sky tess is actually
looking at 85 percent of the sky so it's
looking at the whole sky
and what it's doing is saying hey let me
try and find the nearest brightest
candidates where we can then go and
follow it up for planets because kind of
like you might see someone in a crowded
room you know who's got pink hair and
you say oh they seem kind of interesting
but if you're far away you're never
going to be able to get to know them
scientists are using tests to locate
nearby exoplanet candidates to observe
with the james webb space telescope
which launches next month in december
2021 this powerful telescope will zoom
in on these exoplanets observing their
infrared light and analyzing their
atmospheres
so far scientists have confirmed the
existence of over 4 500 exoplanets in
the milky way and that number continues
to grow
we've only scratched the surface of the
total number of exoplanets in our galaxy
alone they're about 100 billion stars in
the milky way galaxy milky way is one of
maybe 100 billion galaxies
and we know that every star almost every
star we should say has a planet or
probably a few so that means that within
the milky way we've got
hundreds of billions of potential
planets to go out to discover so you
think about that number and the fact
that we've found a few thousand there's
this huge room for discovery and it's
hard to say at what point we'll uh catch
up with the total number of exoplanets
but i'd say there's gonna be a lot more
coming
when we think about planets orbiting
stars it's natural to imagine our own
solar system and how it's configured
with rocky planets closer to the star
and gaseous planets farther out but
that's not always the case so one of the
really common populations of exoplanets
that we find and i'm very fond of them
are called hot jupiters so these are big
planets that are the size of jupiter
really puffy gas giants but they're
about a hundred times closer to their
star than jupiter is and so that means
that you put this ball of gas right next
to the star
and it's kind of like blowing a fan at
somebody with a toupee you're gonna
watch things sort of blow in the wind
and it's gonna reveal some things
and so the reason that we find so many
hot jupiters it's as you might imagine
easier to see big effects and big things
in space than little ones with our
technology and if it's right next to the
star that means it repeats a lot faster
so a year could just be about four days
for some of these planets and so that
means that you know you only have to
watch it for about 12 days to say oh hey
that might be a planet
so with these exoplanet systems we not
only find that the planets within them
can be really diverse and have different
sizes and temperatures and distances
from the planets in our own solar system
but also you find that they could orbit
multiple stars you could have the
alignment be
totally different you could be orbiting
the pole of the star so you might have
seasons every couple of hours on your
planet
and so just because we haven't found a
copycat of the solar system i think what
we're finding is that that doesn't mean
that we are the only ones who look like
this it's just that that's the only
thing that we've seen
yet and there's a lot more to come
once astronomers discover an exoplanet
they use what they know about its
physical properties to picture what it
might look like on its surface if it
even has a surface
[Music]
so you can imagine there are planets
that are just so close to their star
or you know the star has just got all
these properties that make it really hot
on the surface of a planet and it can be
so hot that you wouldn't even be able to
have rock sit there without melting you
might be seeing a world of magma or we
like to call them lava worlds which of
course is totally foreign to us here in
the solar system but we find lots of
planets that have those properties
i can take the mass divided by the
volume of a sphere and say i have a
density and i can compare that to the
density of things i know
so if that density is really light i
might say hey that's a gas giant planet
we can also say i've got this density
that's kinda in between rock
and gas
there must be a good fraction of water
on that planet maybe that's an ocean
world or a water world
it can be so hot on some planets that
the clouds have the ability to
effectively rain glitter or some of the
minerals that are used to form rubies
and sapphires
and there are some planets also if we go
back to our pulsar planets where you've
got that light beam spinning all the
time if you were on that planet it would
probably feel like being at a disco all
the time right because you've just got
the strobe light in the sky
going around
so between that and the fact that you've
got planets that can orbit multiple star
systems so tatooine is not just from the
movies we've found
planets that are orbiting two stars
we've found planets orbiting four stars
a whole number of things you know it's
not one day one sunset it's
lots of sunsets to get to enjoy there's
all kinds of things that i can't even
begin to tell you how excited i would be
if i got to see that because right now
it's just all in our imagination based
on the data
and learning about these alien worlds
can actually teach us something about
our own little blue planet so it turns
out that some of our atmosphere actually
drifts off into space on its own right
it gets enough energy that it says hey i
can overcome gravity i'm out of here and
it's something that's pretty mild on
earth but when you look at hot jupiters
you end up having just huge amounts of
gas right we're talking millions of
kilos and just drifting off into space
so the fact that
i now know hey
you know the earth mars even pluto
they've all got their atmospheres
escaping off into space is something
that you had to see it on a really
extreme scale in exoplanets to
appreciate within our solar system
and so being able to see the diversity
of what's out there and as we're
exploring and finding more worlds it
makes you really reflect back on how
special it is that here we are
and so i often get the question what's
your favorite planet
and people think it's a cop-out my
answer is always earth because this is
the one that i get to experience and
enjoy and i think it's really special to
see how unique that is for now until we
find more that's out there
with so many exoplanets in our galaxy
you gotta wonder could any of these
alien worlds be home to actual aliens
the search for life on other planets
after the break
my parents were showing me a partial
eclipse of the sun when i was 12 and it
blew my mind that anyone
could predict the movement of the skies
like that and it just felt like the
greatest still does feel like the
greatest power imaginable and i wanted
it and so that was it
clara souza silva is an astro chemist at
the harvard smithsonian center for
astrophysics her job is to search the
galaxy for indications of alien life and
in my specific work so looking for signs
of life at a molecular level i'm looking
at things that are so small so far away
that we're talking about
molecules
on atmospheres
surrounding planets
orbiting stars
many many many light years away and to
do that you need to understand molecular
behavior which means understanding
quantum how the quantum behavior of
molecules produced by alien life can be
detected from here
so now i'm a quantum astro chemist
this is so cool
this is like one of the coolest
realizations of a childhood interest
as a quantum astro chemist clara
examines the atmospheres of faraway
exoplanets to look for chemical
signatures of life
but life can take many forms so how does
someone like clara define the term life
in her otherworldly searches
so it is inevitable that we are biased
i'm human i use oxygen and most of the
life that i like also loves oxygen
and so
one of the things when the looking for a
lot is earth earth-sized planets with
thick atmospheres that are oxygen-rich
but it's worth remembering that life is
not one thing for example on earth
for the longest time there was no oxygen
in our atmosphere and life thrived we
then did
fill the atmosphere with oxygen and that
was actually a biological catastrophe
everything died very little survived
that transition it was a absolute global
massacre that we're very thankful for
because out of that came life that
eventually evolved into us
but
that is one of the things that in my
work i think about a lot that earth has
been many planets
life no matter how different and weird
it might be it will still have to be on
a planet or on a moon surrounded by some
environment
and we'll have to make use of that
environment
and when it does it will take the stuff
from its atmosphere and its surface and
its liquids
and will do things with it and then it
will produce waste products because
nothing in the universe is so perfect so
efficient that it doesn't release
something doesn't produce waste
and i look for that waste
so i want to circle over to some of the
molecular chemistry biology that you
were referring to you know i remember
learning about the acronym sponge and
how every life form we know contains
these elements sulfur phosphorus oxygen
nitrogen carbon hydrogen very good and
is it just these chemicals that we know
of that are necessary for life to exist
is there more that you're looking for
could you tell us a little bit about
your search using these elements as a
guide and is it possible
is there non-carbon life forms out there
are there aliens who look at us and
they're like who are these weirdos using
carbon so
sponge or schnapps depending on usually
which side of the atlantic you are um
are not the only elements needed to make
life they're just most popular ones
they're just available
and so it's true that when i do my work
particularly when it's really
computationally demanding i start with
sponge schnapps i start with the obvious
elements
and so
yes these are popular and they're
popular for a reason they're really good
at variety you get a lot of biochemical
variety from these elements a lot of
interesting evolutionary choices can be
made with these environments with water
as a solvent it's a rich playground for
life
and so we do start there but i certainly
don't stop there
life uses other more obscure elements
currently in my
database of biosignatures that i develop
i consider 16
367 different molecules wow all of which
i think could be associated with life
and detectable on alien planets so
that's a lot of potential signs of life
so i definitely try to not create too
strict a boundary on my expectations of
life a biosignature is any
characteristic that can be considered an
indicator of life clara's research
focuses on molecular biosignatures in
the atmospheres of planets but not every
exoplanet is included in her searches
for example i put boundaries when i look
where if it's so
high pressure and so hot that complex
molecules would just disintegrate
i'm calling that a no-go so there are
limits here a planet that has no
atmosphere and no safe subterranean
environment like an underwater liquid
ocean is also not good a planet that is
so close to its star that gets destroyed
by stellar winds and radiation at
regular intervals that's probably not
good either but outside those limits
there's a huge variety of planets and
stars that they orbit and we look for
anything anything weird
so no we're not just looking for life on
earth like planets we're looking for
life on moons of planets
we're looking for life on planets where
we know very well we would die a quick
and horrible death
so we very much look at anywhere that
could be considered habitable by some
definition
if an exoplanet is determined to be a
good candidate for hosting life
astrochemists like clara analyze the
molecules in that planet's atmosphere to
look for biosignatures
molecules interact with light
and that is a universal truth
we can experience it here and we can
watch it happen everywhere else in the
universe and so when we get light from a
star we can break up that light into a
rainbow
we have basically fancy prisms that
break up the light from stars
and when we do that we get a stars
rainbow
and if a planet with an atmosphere
containing molecules crosses in front of
our star we might not see that event
because the planet is so small compared
to the star and they're both so far away
but the light from that star can go
through the atmosphere of that planet
and when it does
molecules in that atmosphere will absorb
some of the colors of the rainbow
and so we see
this beautiful stellar rainbow
once every orbit change
and some colors go missing
and we know from work here on earth that
for example if light goes through an
atmosphere that contains water then
there's very specific colors of the
rainbow that water will absorb very
different from if that light goes
through an atmosphere that has methane
or phosphine or ammonia or molecular
oxygen and so basically we see what
colors are missing from this rainbow and
we know what molecules that light must
have gone through
clara has a favorite molecule to search
for in the atmosphere of exoplanets
phosphine
phosphine became very much my favorite
molecule
in that
nothing i will ever love will produce
phosphine phosphine is an extremely
dangerous molecule for the life we find
pleasant
but
not all life will like oxygen
and there is still on earth
environment and life in those
environments that doesn't really like
oxygen these are anaerobic life forms in
swamps and
in our intestines
and at the bottom of lakes
and this life is trying to avoid oxygen
as much as possible
and that life produces phosphene so when
they figure that out i thought
what if a whole planet was like that
we as a planet used to not be filled
with oxygen most planets we have found
are not filled with oxygen
so maybe life there could produce
phosphene
and so we often look for these molecules
on these alien planets but the question
becomes if you find these molecules have
you found life
or could there be some strange
geological event or
thunder and lightning falling on some
type of liquid that could produce these
molecules without any life being needed
we call these false positives for life
and most molecules have them
most molecules that life makes are not
that hard to make and so the universe
makes them accidentally spontaneously
with no need for life and how do we tell
the difference
and that's what makes phosphine so
special to me because phosphine is
almost never made spontaneously so it'll
be hard to find it but if we do
it will very likely mean life because it
is so difficult to make
and that just seemed extremely cool
scientists aren't just scanning far away
exoplanets there are other planets in
our own solar system that might host
alien life and since phosphine could be
an indicator of life it was all the more
interesting when clara and her team
found phosphine in the clouds of venus
in september 2020 but the data are still
under debate
this is
done very much at the edge of technology
with sensitive noisy data that we're
still arguing about
there are ways of processing the data
where the signal disappears altogether
and there's ways of processing the data
where the signal is there loud and clear
and statistically significant
and even teams that agree that the
signal is real disagree on whether it
must be phosphine there are other
molecules whose quantum behavior can
mimic that of phosphine in some
circumstances like sulfur dioxide
ultimately we need to collect more data
to know for sure and if we do
it will be wonderful not just because it
means we have neighbors
but because we have neighbors producing
phosphine my favorite sign of life
gazing at distant alien rainbows isn't
the only method we've used to search for
alien life the seti institute short for
a search for extraterrestrial
intelligence has been looking for
evidence of technological civilizations
in our galaxy since 1985 but so far we
haven't had any luck with
extraterrestrial communications no
matter what hollywood says we have a
ships in the night problem
we have had let's say a couple of
centuries of communication and less than
that of listening in
it is possible that we as a civilization
will obliterate ourselves in only a few
centuries more on earth we've had i
think historically something like five
billion species
and only one intelligent and barely so
and for very little time
and so it becomes very easy to imagine a
galaxy full of life
full with life teeming with life
everywhere but very few civilizations
able to communicate for long enough
before they're obliterated
what exactly are techno signatures and
how do we actually search for them on
other planets or try to detect them
so
complex pollutants are a very depressing
but very reliable
signal for life
so if aliens were looking at earth and
detected the pollution we have way too
much of in our atmosphere they'd be like
oh there's probably life there but they
would be
sure that they got really lucky and
caught us just before we completely
destroyed the environment and ourselves
so looking for complex pollutants
i would love to find them because there
will be no ambiguity
but i would be very worried for my alien
colleagues and their longevity
so do you think this will humble
humanity if we do find life like what
what difference do you think it'll make
in every person's mind
i certainly hope so i think a little
humility would go a long way
i think people sometimes talk about how
it will unify us because now we have
this you know common enemy and i
certainly hope that does not happen
that we don't
just transfer our desires for us and
them to
a galactic scale
but i i certainly hope that it will feel
humbling and comforting all at once
that's how it feels to me
but that's why we need more than quantum
astro chemists and
engineers we definitely need
philosophers and
lawyers and
poets and artists to make sense of it
all
and odds are of the hundreds of billions
of possible planets in our milky way
galaxy
some number of them are likely to host
life
so my favorite way of thinking about
this is
are we special or are we not
and
the sun is a wonderful star i love it
wouldn't trade it for the world but is
not a particularly special star
the molecular cloud that formed our
solar system
had wonderful components in them but
they weren't special they weren't rare
they were actually extremely abundant in
the universe
the planets in our solar system
have a reasonably unusual configuration
with the planets themselves they're not
rare at all we know of thousands of
planets like them
and so
the sun is not special
our planets aren't special
our origin story is not special
so
i think it is foolish to believe that
life is special on earth i think life is
inevitable
because
any theory that starts and ends with the
exceptionalism of us is likely to be
wrong or at least mathematically
implausible
so life is resilient
life is great at finding opportunities
and so i think life is common
but whether intelligent life is common
there i have very little hope there's
only us barely so and for a blink of an
eye
[Music]
nova now universe revealed is a
production of gbh and prx it's produced
by terence bernardo jenny cataldo ahri
daniel caitlin falls and jocelyn
gonzalez julia court and chris schmidt
are the co-executive producers of nova
suki bennett is senior digital editor
christina manan is associate researcher
robin kasmer is science editor robert
boyd is digital associate producer shyla
duff is digital video intern and devin
maverick robbins is managing producer of
podcasts at gbh
i'm a look patel
we'll be back next week for
get this a journey where we travel into
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