and we have a really special talk for
you tonight somebody who just popped up
on my email saying oh I'd love to give a
talk and I was like oh this is great
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want to follow me unfortunately the
weather is not permitting tonight to
those of you who brought the umbrellas
in no definitely not pretty and
unfortunately the observatory is not
permitting the observatory is closed for
repairs until further notice they had
some problems with their dome and they
emailed me today that they don't know
when they'll be able to reopen
so you
go to md dot space grant org you will
find this webpage over here on the right
and the observatory status will not say
check back on Friday it will say that
check back next month or in a few weeks
and will be able to tell you when the
repairs will be done ok
so unfortunately for the next couple of
months possibly we will not have the
Maryland space grant observatory ok all
right now our news from the universe for
November 2017 the first story tonight a
wrinkle in space-time as you know I like
to make small puns here this of course
is playing off Madeleine L'Engle famous
story a wrinkle in time and what I'm
talking about of course is the LIGO
project the laser interferometer
gravitational-wave Observatory which I
told you about early last year has these
two detectors one in Hanford Washington
one in Livingston Louisiana and you can
see they are these big long arrays that
they send laser beams down each one of
them and they the Blazer beams bounce
off a mirror and come back and they
measure the distance very very very
accurately so that when the distances
change they could tell by an incredibly
small amount and they did measure an
incredibly small amount of change and
see what was observation done I can't
remember the exact date of this
arbitration but this was the detection
of a black hole black hole merger that
was about 1.3 billion light years away
the first detection of gravitational
waves and it was seen here is the data
versus the predicted for Livingston and
same for Hanford in fact it was detected
in both of them and with the proper time
delay per light to travel between them
first detection of gravitational waves
and on October 3rd of this year it was
awarded the 2017 Nobel Prize in Physics
to these three gentlemen of the LIGO
Virgo collaboration for the decisive
contribution
to the LIGO detector and the
observational gravitational waves now we
all sort of knew this was going to come
because I could detect gravitational
waves for the very first time
yeah that's worthy of a Nobel Prize I
personally did not expect it to come so
quickly all right but you know since the
discovery of those first blackhole
mergers they've discovered three or four
more black hole black hole mergers so
they're getting more observations but
last summer on August 17th they also saw
a neutron star neutron star merger okay
so black holes are even alright so
neutron it's a star can end up in
several different ways okay a medium
mass star low mass star ends up is
what's called a white dwarf and that's
about the the the the density of the the
atop the at the atom okay and it's
supported by electron degeneracy
pressure yada yada yada but it's about
the density of an atom about the size of
Earth okay all right and then there is a
if you are more massive you can collapse
down to what we call a neutron star
which is about the density of an atomic
nucleus okay and that's about the mass
of the Sun compacted to about ten
kilometers across or about the size of
the Baltimore Beltway okay so take all
the Sun could pass down to the Baltimore
Beltway size a ten kilometer cross and
that's what you get a neutron star a
black hole goes even further than that
is even more massive even even higher
density okay so these neutron stars when
they collide they're incredibly dense
when they merge together they will also
produce gravitational waves but not
really as strong as a black hole black
hole but this neutron star collision was
only 130 million light years away which
I know it sounds pretty far but compared
to the 1.3 billion light-years away that
black hole black hole merger was is
actually only 10% of that distance so
they're able to see this neutron star
neutron star collision with LIGO and
Virgo virgo is the
version of Lego however what made it
even more exciting is it also was
observed in optical light using both the
LIGO detectors here in the US and the
Virgo detector in Italy they were able
to relatively relatively accurately
determine where it was on the sky and
astronomers were able to search for that
point on the sky and found that there
was an excess of radiation coming from
this dot within the galaxy NGC 4990 3 so
they actually able to do follow-up
observations and neutron star neutron
star collisions will have a lot of
material around them and that will
generate a lot of optical light okay so
this is Hubble's observation from August
22nd through August 28th over six days
watching did you try and start a neutron
star clip the light from that collision
fade away
all right and it's not just that it was
seen by Hubble matter of fact Hubble was
not the first one to see it it was
actually first seen by family in gamma
rays so it was seen in gravitational
waves by LIGO and Virgo it was seen in
gamma rays by Fermi integral and Swift
it was seen in x-rays by Chandra it was
seen in visible light by Hubble it was
seen in infrared light by spitzer and it
was seen by visible and infrared light
by things like pan-starrs and other
ground-based observatories so this is
when astronomers can really get to work
when it can really characterize the
event when we see it in this many
different wavelengths we see what's
happening at lots of different energies
and we can understand the event a lot
more the black hole black hole merger
that was that you know that won the
Nobel Prize there were no follow-up
studies we didn't see it in any other
wavelengths this neutron star neutron
star merger we were able to see in other
wavelengths were able to get different
characteristics of it and we're able to
understand the processes that are going
on and the basic result so far has been
that hey it sort of fits what we think
happens you know which is actually kind
of crazy ideas
you know and we say all right well this
is our predictions we usually expect to
be surprised by old nature behave
slightly differently than we predicted
most of the predictions seem to be
working out pretty well for this
although there was one thing in terms of
seeing it in ultraviolet that they
didn't expect and the fact that it was a
relatively faint gamma ray okay it's a
short duration but it's a faint
gamma-ray burst
okay the short duration bursts for
something so close she had been larger
and they're not quite sure why but these
are all the questions that come up when
you have this many different ways of
looking at it and are able to study it
in so many ways so this not only have we
moved into gravitational wave
astrophysics but we've got follow-ups to
be able to correlate it which makes it
so much more valuable our second story
tonight on the trail of asteroids now
Hubble had this amazing project called
the frontier fields okay and the
frontier fields looked at six really
massive clusters to look for
gravitational lensing so this is the
mass of galaxy cluster Abell 370 and all
these streaky things in here are
gravitationally lens arcs okay and we've
talked about that a lot and at the same
time while they were doing the well
they're looking at the galaxy cluster
they also looked at what they called
parallel fields so one detector of
Hubble was looking at the cluster
another detector was looking at the
parallel field and then actually they
rotated and then that one detector of
the parallel field and the other
detector look at the cluster okay and
they spent about a hundred hours of
observation time on each of these
clusters well these are the cleaned up
images that you see okay and of course
the real observations have lots of you
know cosmic rays and other things that
happen you know detector artifacts that
have to be cleaned up but there's also
another thing that they had to clean up
out of this these images that is
illustrated by this movie so as this
movie plays you'll start to see these
little streaks appear
and they're numbered 1 through 7 because
these are seven unique asteroids that
passed through the field over the
hundred hours that Hubble was observing
now Hubble doesn't observe it
continuously it does a bit of
observation that'll go off and do
something else and we'll come back to
the field and do some more observation
etc which is why number seven here you
can see is split into four separate
little loops alright and why are they
streaks and curved loops well
Hubble and Earth are moving relative to
the asteroid while we're taking
observations so the asteroid actually
ends up streaking and the parallax
motion produces that little curve on
there alright so for a bell 370 and it's
parallel field here are the cleaned up
images and there are the images with the
asteroid streaks now you'll notice we
use the movie on on the parallel field
simply because there are already these
streaks in the gravitational lens those
are actually galaxies that are beyond
the gravitational lens but if I blink
back and forth you can see the asteroids
and where they appear on the field and
this is kind of cool because what you've
got here in one image is you've got some
things within the solar system as well
as you've got things that are billions
of light-years away and it reinforces
one of the things that we have to deal
with an astronomy when you look out into
the universe it's the sum of everything
that you're looking through the solar
system to the galaxies to the distant
galaxies all the way to the edge of the
universe that when you take an image
you're combining all that into one of
those and here you can see some of the
nearest things and some of the father's
things in the universe all combined
together that's kind of cool alright so
now it will go to our featured speaker
and our featured speaker tonight let's
see if her laptop takes over yes it does
his doctor Elizabeth Tasker and she is
from the originally from the UK
she did her undergraduate work at Durham
University and then did her graduate
work at University of Oxford then she
came across to the United States and
Canada and did some post doctoral work
here before going even further from home
where she is an associate professor at
the Japan aerospace exploration agency
and I love JAXA because that's a great
acronym to say it's almost it's it's
like NASA but it's sort of an intriguing
sound would Jax I just you know sounds
as good as NASA in terms of a Space
Agency she does her research work on the
formation of stars and planets by doing
computer simulations and today is a very
special day for her because she has a
book that is being published today and
I'm sure she'll mention that in her talk
ladies and gentlemen dr. Elizabeth
Tasker
thank you very much is this something
good okay so today I'm going to be
talking about planets especially those
beyond our solar system but I'm going to
start with what I hope is a vaguely
familiar image in a minute so I'll be
starting with what I hope is a vaguely
familiar image there we go so I hope
these guys look somewhat familiar to
everyone and I say this is a Sun and
then just past the Sun we have our four
smallest planets Mercury Venus Earth and
Mars and just past Mars we have this
band of rubble rubble rocky leftovers
from the planet formation process that
we call the asteroid belts which also
contains the dwarf planet Ceres and then
beyond the asteroid belt we have the
giants Jupiter Saturn Uranus and Neptune
and then we have this another pile of
rocky leftovers from planet formation
which is the Kuiper belts and of course
it's most famous member is the dwarf
planet Pluto that we never really talk
about that anymore and you are here
alright so if you were to base all our
understanding of planet formation on our
solar system we would note that you have
two types of planets you have rocky
planets so these guys Mercury through to
Mars and here you have a solid surface
with a relatively thin atmosphere and
then beyond the asteroid belt you have
gas giant planets where most of their
volume is taken up with their atmosphere
around a much smaller dense central core
and this colossal atmosphere results in
absolutely crushing pressures near their
core so much so that in fact our
hydrogen on Jupiter by the time you
approach Jupiter's core it becomes so
dense that it starts behaving as this
kind of metallic compound
so until 1990s these were all the plan
it's we knew and we didn't think that
our solar system was the only one out
there but we haven't actually seen any
others so nothing was definite but then
everything changed so our Sun is one of
about a hundred billion stars in the
Milky Way galaxy and when we talk about
extrasolar planets we mean extra as in
outside and a solar as in of the Sun so
an extrasolar planet or exoplanets is
any planet that is not in our solar
system and the story of extrasolar
planets begins in 1990 when the Arecibo
radio telescope in Puerto Rico
repairs however were actually structural
cracks so around the same time a similar
radio telescope in Green Bank in the
u.s. also has structural cracks which
were ignored and the whole thing
collapsed so in a fit of panic Eris II
was like okay we've got the message
we're gonna fix this
but during repairs the telescope was not
taken completely offline
but it couldn't be moved so typically
during a night so the telescope will
move very slightly across the sky as it
tracks objects but during these repairs
nothing could be done it had to be
absolutely stationary and this made it
unfit for almost all projects however at
the time was a postdoctoral researcher
called Alex bull Shen and he asked to
use a telescope for a month-long survey
because this survey could be done while
the telescope wasn't moving and normally
such a proposal would never have gone
through because he required half the
telescope's time and this was the
biggest telescope in the world for radio
so people would be like yeah no but as
it happened no one else could really use
it he was based the telescope and they
said fine and what Alex wanted to find
were dead stars called pulsars so
actually we've just had a very nice
summary of these because a pulsar is
what forms when a star that is much
larger than our Sun more than 8 times
eventually reaches the end of its life
and it runs out of fuel to burn and when
that happens the star dies in a
supernova explosion and the bit that's
left behind collapses to incredible
densities so dense that its atoms
actually starts to disintegrate and the
protons and the electrons inside the
atoms and so we therefore call these
neutron stars which is exactly the same
source of the gravitational waves
mentioned earlier however as yeah and as
mentioned these are tiny so only
city-sized or indeed the
the Baltimore Belt and yet they weigh
between 1.4 and twice this mass of the
Sun so they're incredibly dense objects
and as they collapse their magnetic
field also strengthens a lot and this
magnetic field causes any remaining
charges left on the neutron star to be
ripped off and fired into the cosmos as
powerful Jets
now if these Jets happen to swing by the
earth as the star rotates then we see a
periodic light pulse and therefore we
call these April's are now the accuracy
for these pulses is incredibly high it's
so high that when they were first
discovered they were thought that they
might even be extraterrestrial sources
but in fact when more sources were
discovered across the sky it was
realized that actually a natural process
must be causing these but their accuracy
is such that it rivals that of atomic
clocks except for this one pulsar that
Alex Vause Shem saw so this pulsar was
called PSR b12 57 plus 12 that very
catchy name and for this particular
pulsar so PSR is pulsating source of
radio and then that's completely our
memorable letters and numbers is the
position in the sky but for this
particular pulsar the time between the
flashes changed very slightly and it was
ultimately concluded that this was due
to two planets orbiting the Pulsar and
as the planets orbited the Pulsar the
Pulsar wobbled very slightly due to the
planet's gravity and as it wobbled his
distance from the earth was changing a
tiny amount and this was causing the
flashes to have to travel up slightly
further and slightly less far and
therefore their timing started to become
off so the discovery was two planets
which were again very imaginative named
PSR b12 57 plus 12 B and C and they were
roughly four times
mass of the earth and their years
they're all bits around the Pulsar were
65 and 98 days so for comparison but
Korea our innermost planet has an orbit
of 88 days so if these two were around
our own Sun they were sick either side
of mercury and they are a rather
staggering two thousand light years away
which tells you exactly how sensitive
this technique was now these were the
first planets ever to be found outside
our solar system and the discovery was a
pretty enough published in the
international journal Nature on the 9th
of January in 1992 however it actually
was leaked earlier than that by the
British tower British broadsheet
newspaper the independence on the 29th
of October in 1991 with the headline
radio astronomer finds two planets in
distant space now Alex Borstein was
approached by the independent and asked
for a quote and this must have been
fairly nerve-racking because obviously
he wanted this discovery to be published
in a journal such as nature but if news
gets out early sometimes nature might be
like why it's never longer news so we
don't want it as a result there's a very
guarded comment by Alex Vause shown here
saying professor volscian was not
prepared to talk about his research
because he feared it my prejudice the
chances are being published in a
scientific journal however despite this
even after the nature publication there
was very little public notice which when
you think of the fuss that new
discoveries have nowadays where you have
multiple reports against the whole world
media is very surprising that the first
planets we ever found no one really
talked about indeed at the time when my
parents were taking the independent and
this newspaper must have sat on our
kitchen table and I don't remember it at
all so what was the problem was it that
just pulsar planets were just a bit too
weird
I mean you know pulsars dead stars can't
really relate to those hopefully never
will be able to relate to those maybe
people just didn't really feel a
connection connection
so as a result these are sort of
overlooked but pulsar timings
unsurprisingly it can only be used to
find planets around pulsars so what
about finding planets around regular
stars so we found the Pulsar planets
because there is a slight change in the
timing of the Pulsar flash due to this
wobble in the Stars position because of
the planets orbit so could we do this
with normal star light as well and
obviously the answer is yes or I would
not have taken us in this direction so
when you have a more regular star you
have a system like this so here are we
on the earth there's our star here and
here is our planets and due to the
planets orbit the star is going to make
a small wobble now as the star moves
away from the earth its light that's
reaching us is going to get stretched
out and this is going to cause it to
become redder now as it swings around
the other side of it's wobbling position
the light waves are going to become
compressed as the star starts
approaching the earth and when they get
compressed
they light gets bluer so what you see is
this tiny shift from red to blue to red
to blue as the star wobbles due to its
orbit from the planet and we call this
the radial velocity technique or
sometimes the Doppler wobble technique
however this is not a big shift the tiny
tiny shift in light and it's incredibly
hard to measure
however in 1988 a new technique was
established so in this technique you
have your star and missing lights and
you've got your telescope and in front
of the telescope we're going to put a
jar of gas and the point is here that
here is your star and it's light is
going to be slowly shifting from red to
blue tiny tiny tiny shift but our jar of
gas is also going to be a missing light
that is not shifting because it's
completely stationary in front of our
telescope so what it is is it's bit like
slamming down a ruler and because you
have a stationary point with which to
compare
Starlite it becomes much easier to
measure tiny shifts so this allowed us
to have much higher accuracy when trying
to measure this radial velocity change
and using this technique as early as
1988 a wobble was seen around a star
called gammas EFI could this be from an
exoplanet so there were some problems
gammas EFI is part of a binary star
system meaning it has a companion star
and the two stars orbit one another so
this was the first question mark would
we even expect planets around a binary
system if you had a sister star would
that disrupt the planet formation
process secondly the star that was
wobbling was thought to be a giant star
now this is the phase that stars reach
near the end of their life and as they
approach the end of their life they get
quite crotchety so what you find is the
outer layers of the star start to have a
lot of vibrations and pulsations that
look just like a small bubble from a
planets so the astronomers were a bit
suspicious and in the end they concluded
oh it's a giant star it's a binary we
don't really expect to see a planet here
there are lots of other reasons for this
possible wobble now we see a wobble but
it's not a planet and when they
announced that they missed discovering
the first exoplanets because this wobble
was due to a planet but its discovery
was not finally announced I think until
2013 so the first discovery that
actually everyone remembers is a planet
called a 51 pegasi B that was found in
1995 with this same radial velocity
technique with a light shifting from red
to blue and it was the first planet that
was found around a star like our Sun
rather than a giant star or a long-dead
star like a pulsar and it opened the
floodgates to finding thousands more
because it proved this radial velocity
wobble was detectable
we could see it and from there we
started discovering planets in droves
however this planet was also rather
strange so back to our own solar system
and one thing that we note is there are
giant planets these huge gaseous ones
sit a long way from the Sun we have the
rocky ones close and we have the gaseous
ones further away but this planet 51
Pegasus B was a gas giant on the orbit
of just four days
so if remember mercury is 88 days that
puts 51 Pegasus B really really close to
its star so how do you form a planet
there well let's just take a step back
and ask why this is at all surprising so
young stars are surrounded by discs of
gas and dust known as protoplanetary
discs now this image here is an artist's
impression however this one is not this
is a genuine image of a protoplanetary
disc around a young star taken with Alma
and in this disk of dust and gas dust
starts off at micrometer sizes and it
starts to collide and stick so we go
from a chromatid to millimeter to
centimeter to meet her sizes and now
we're starting to look a bit like the
asteroids and eventually gravity finally
gets seriously interested and it
squishes our newly formed planet into a
ball and we start to say yes okay I
notice that's a planet
now there is one subtlety to this
process I'm sure will astound everyone
if you are forming near the new star
you're hot on the other hand if you're
forming a long way away you're cold and
this has one important effect there
comes a point as you step away from the
star that ice starts to form and we call
this point the ice line the snow line or
the frost line if you are inside the ice
line and closer to the star water is a
vapor on the other hand if you're the
other side of it
then it is a solid and that means you
get a huge boost in planet-forming
material the other side of the ice line
because here you've got your silicates
like what the earth is mainly formed off
but out here you've got the silicates
but also a huge a number of ices so you
get a big step in density it's like
being given a whole new leather set so
as a result we expect small planets to
form here where we have less building
material and giant planets to form here
where we have a lot more and this should
be the same around every star because
the only assumption I put in here is
that you're hot if you're close to the
star which you think would be
universally true so how do we get a
planet here there should be barely any
building material there and yet 51
pegasi B was roughly the same size as
Jupiter so this is what we think happens
as the planet grows it eventually
reaches the size of Mars
now Mars is not a big planet it is
roughly a tenth of the mass of Earth but
however at that point the planets
gravity gets strong enough that it
starts to pull on the surrounding gas
and dust that still circle the young
star and this gas and dust pulls back
and the result is like being on a
running track so here you are and you're
going to be running this circular race
with two buddies a buddy and a detective
and a little later on oh no I'm sorry
yes there's been a terrible addition
where for some reason you've been tied
to your friends with a piece of loop but
a little later on war here now your
bunny friend was on the inside running
track and as I'm sure everyone remembers
from school PE lessons that gives you a
very unfair advantage so they're on a
much shorter running track and he's
pulled ahead of you on the other hand
your detective friend was on the outside
running track and had further to go and
therefore she is a little bit further
behind but you're still tied together
with this rope
so you start to feel a force with the
bunny pulling you forward and a
detective pulling you back and the same
thing happens due to gravity
with our new planet in our disk where
the gas closer to the star is pulling
ahead and dragging on that planet to
move it forward
whereas the gas further out is pulling
back and trying to slow that planet down
and as a result you end up in this tug
of war and the net result is usually
that the planet feels a push inwards so
what this means is oh yes and we call
this migration so what this means is
your planet can start far out it can
form where there's lots of ice there's
lots of building material and it can get
big and jupiter-sized but it can then
migrated inwards due to this pull from
the gas disc and when the gas disc is
finally evaporated by the star you end
up with a large planet close to the star
and we call these hot Jupiters because
they're jupiter-sized and hot so this
explained 51 Pegasus B but what about
the pulsar planets what could explain
them and were they even surprising well
the problem with pulsar planets is as
they briefly mentioned pulsars start
with an explosion a supernova so when
they explode if they still have planets
orbiting them too awful things can
happen to those planets the first is one
could be vaporized the second is the
shockwave from that explosion can kick
the planet out of the solar system so
generally speaking we do not expect
these planets to be able to survive this
supernova explosion so how on earth do
you end up with a pulsar orbited by
planets well evidence to what might have
happened was discovered in 2012 when a
tiny star was found that seemed to be
flashing red and then blue and it turned
out to be orbiting a pulsar every and 93
minutes which is actually the average
commute time in the UK
but as this planet orbited the Pulsar
you actually started to see different
sides of it so if the Pulsar is here and
you are the earth first of all you're
seeing the front side and the front side
was being hit by the pulsars Jets and
becoming very hot however as the star
orbited you started to see the backside
and this was much colder so what you
were seeing was intermittently the hot
side of the star then the cold side
seeing this flash from red to blue and
back again but because the Pulsar was
being hit but push the star was being
hit by the Pulsar Jets the Pulsar was
blowtorching it to pieces so you have a
system a little bit like this one where
the pulsars Jets were ripping over the
star and shredding it and as the star
ripped as a pulsar ripped this other
star to pieces and discs formed from
it's ruined body and in this disk
planets could start to fall again
so pulsar planets have rather a morbid
origin they require another star to be
shredded to pieces and it's broken body
to form the birth ground of new planets
so these first finds were strange worlds
but later we found many planets that
were much closer in size to the earth
orbiting around normal stars around now
we have found I think about three and a
half thousand planets beyond our Sun and
roughly a third of those have a radius
that is less than twice of that of the
earth so this brings us to the obvious
question can we find earth 2.0 well
let's look what we know with an example
that hit the news at the beginning of
this year and the telescope that made
this news with a telescope called
transiting planets and planetesimals a
small telescope and it's a 60 centimeter
telescope in Chile and if you take these
letters very slightly randomly you can
spell trust which
entirely coincidentally because it's a
Belgium telescope also happens to be the
name of a Belgian beer but in February a
Trappist made an incredible discovery
it found a star orbited by seven planets
now as a telescope that made the
discovery the star was named Trappist of
one and the planets became Trappist one
b c d e f g and h so was this a solar
system like our own well the press got
pretty excited
we had headlines like NASA's discovery
of a solar system with seven earth-like
planets will change how we hunt for
alien life we had four new scientist
exoplanet discoveries seven earth-sized
exoplanet s-- may have water or from the
guardian exoplanet discovery seven earth
sized planets found orbiting a nearby
star clearly if you just read the press
headlines you would think we'd found
this clearly seven earth septuplets
all identical probably already have
Starbucks on them but what do we really
know about them well these planets were
discovered not with the radial velocity
technique but with the transit technique
and this is when the planet moves in
front of the Stars surface and causes a
tiny dip in the Starlight and it's how
the Kepler space telescope finds its
planets so in the case of the Trappist
seven we see seven periodic dips as the
planets pass by the star surface now
transits usually give what they do they
give you the planet radius the physical
size of the planet so the bigger the
planet the more light it blocks out and
you can pick this up with the transit it
doesn't normally tell you the planet
mass normally but the Trappist planets
were slightly different so Trappist one
has many planets it has seven and as
they orbit the star the planets pull on
one another and as a result this slope
change the time for each orbit so this
is like if you're running around you're
circular running track again but this
time you've taken your dog along for the
run and your dog is not always terribly
cooperative sometimes your dog is
pulling you forward and that means you
make your lap time slightly quicker but
sometimes your dog just wants to sniff
stuff and it's pulling you back and so
your lap time becomes slightly slower
and these changes in lap time can be
measured due to the planets pulling on
each other and we call this transit
timing variations or TT V and we and we
have a really special talk for you
tonight somebody who just popped up on
my email saying our website for more
information if you go to your favorite
browser public talks Republican Series
you can't say you could say Space
Telescope probably to all this with the
list of the upcoming lectures watch live
online you can watch the past lectures
all the way back to 2005 so that's 12
years and you can also sign up for one
or two emails a month is too much you
can also unsubscribe to or if you are
fashioned to the list if you have
comments or questions so the great
bernard is going to have Ward effect on
your lap time so T TV actually gives the
mass of the planet in addition to the
planets physical size so what did we see
with these seven worlds well let's look
at radius as a
action of earth-mass and we see we have
three planets with almost exactly the
same size as Earth and three planets
with a slightly smaller size on earth
and one slightly larger and if we look
at the masses we have anything between
40 and 140 times the matter percentage
of the mass of the earth so we have
roughly we have seven roughly earth
sized planets so here is the question
does earth size mean earth-like well
what else do we know about this system
now on earth a year so our lap around
the Sun takes approximately 365 days if
you were on Mars it would take 687 days
if you're on Venus it'll be 225 and
Mercury would be 88 the Trappist planets
the one furthest from the star that's
going to take the longest orbital time
will take 20 days twelve days nine days
six days for 2.4 and 1.5 days to make
that orbit so if these were around our
Sun all of these planets would sit
inside Mercury's orbit so does this mean
that the Trappist one worlds are in fact
larva worlds with melted crusts of magma
well something fortunately saves us and
that is that Trappist one is very dim if
we were to compare the size of the Sun
with a basketball
then trakis toin only has the size of a
golf ball and it has only a thousands of
the sun's brightness so that means you
can afford it to be a lot closer but not
that much hotter so if we compare
instead the amount of radiation the
planets receive then the amount of
radiation that we get from the Sun over
Venus Earth and Mercury is approximately
equal to the amount of radiation
received by planet c d e and s
so very similar radiation for these
planets so what about water well when we
talk about water especially with
exoplanets we typically talk about
something called the habitable zone and
this is the location where an earth-like
planet could have water on its surface
so you could imagine taking the earth
and giving it a push towards the Sun and
at the point where our water and our
oceans become steam and evaporates that
is the inner edge of the habitable zone
conversely if we took the earth and
pushed it outwards then there comes a
point where the oceans freeze and that
is our outer edge of our habitable zone
so if we look at the planets around
Trappist one the same habitable zone
exists here over planets EF and G so
does that mean we have three planets
with water well not so fast
we have to look at the small print of
this habitable zone contract the
habitable zone is defined as follows the
habitable zone is where an earth-like
planet can maintain liquid water on its
surface and a small print here is
earth-like so if you have a planet that
is not an exact Earth clone it heavy has
a larger mass a smaller mass a different
atmosphere different rock type there is
no guarantee at all that it will have
water inside the habitable zone indeed
of the exoplanets we've discovered we've
found roughly five times as many gas
giants like Jupiter inside the habitable
zone as we have planets that may have a
rocky surface so then the question
becomes these three planets they're
earth-sized but are they earth-like
earth-like enough for the habitable zone
to be meaningful
so with exoplanets we typically know two
things and this doesn't just apply to
the Trappist one it applies to all
exoplanet discoveries we typically know
either the planet radius if it's found
through the transit
technique looking at that light dip all
we know the planets minimum mass if it's
found from that red and blue Doppler
wobble and occasionally like the
Trappist system we know both so we know
something about the planets physical
extent we also know how much radiation
it receives from the star now the small
print here is this is not the same as
surface temperature and the warning to
that is in our own solar system so Venus
receives roughly twice the amount of
radiation that the earth does and if you
were therefore to make a guess as a
surface temperature of Venus you would
guess 27 30 Celsius which is 19
Fahrenheit maybe anyway it seems very
pleasant we should go there for a beach
holiday but in fact that is not true of
the surface of Venus the surface of
Venus is at 460 Celsius it doesn't even
really matter whether it is in
Fahrenheit it's just ridiculously hot
and the longest a spacecraft has ever
survived on the Venetian surface is less
than two hours and the difference is
Venus is huge atmosphere which we cannot
tell currently at a distance when we
look at exoplanets so we don't know
anything about the surface conditions of
these new worlds we found and what do we
need to know to say yes this is
earth-like well most certainly size is
important if you have a planet that's
Jupiter sized we can be pretty sure that
is not going to have a solid surface
it's not going to be earth-like so you
definitely need to be in the ballpark of
the Earth's radius and mass but our
planet also has a protective magnetic
fields and this protects us from the
flares from the Sun that would strip our
atmosphere instead charged particles for
the Sun get caught safely in our
magnetic field and come down as the
northern and southern lights at our
poles occasionally we might have some
damage to our GPS systems but the
surface of our planet is mercifully not
sterilized volcanoes so you might think
a planet with no volcanoes sounds like a
rather good idea but it turns out
they're rather important for our
atmosphere
during the early earth we needed
volcanoes in order to get the atmosphere
that ultimately developed life and
indeed now it's one of the ways that
greenhouse gases are controlled over
geological timescales rock-type again is
how we control our greenhouse gases over
geological timescales and how our
planets manage to maintain very good
conditions for forming life for so long
the presence of water just because you
can support water there's no guarantee
you have water to support so as I
mentioned the earth formed inside the
ice line this may have meant it was
actually formed as a dry planet and as
how water could well have been delivered
later on by icy meteorites scattered
inwards by the giant planets like
Jupiter and Saturn so if you have a
different planetary system without those
big beefy planets outside you do you get
a scattering of icy meteorites to
deliver water we're not sure and plate
tectonics our crust our surface is
divided up into chunks and these chunks
allow our planet to cool which helps
generate our magnetic fields and when we
observe a planet around another star we
only know about the first two we don't
know about any of these other effects in
the moment so it takes a lot to be like
Earth and we don't know very much about
any of these exoplanets however in the
case of Trappist one unusually we do
know one other thing the planet orbits
of Trappist warm are in resonance and
that means that if you look at the time
for each planet to orbit the star you
see something rather interesting in the
time it takes for Planet B to orbit the
star twenty-four times it takes planet
planet C orbits 15 times 15 not fifteen
point five not fifteen point three not
fifteen point one two seven eight three
it's an exact integer or very close to
it
and the pattern continues 24 15 nine six
four three two one very close to being
exact integer ratios of one another
how does this happen it seems like a bit
of a coincidence so what we believe
happens is that if the planets are born
far from the star and they go through
this migration process to come further
in if you have multiple planets doing
this and their gravity pulls on one
another they can end up locked in these
resonance positions so as they both
migrate in their orbits at some point
will sync up to exact ratios and this
turns out to be very stable so once you
hit this sweet spot you tend to stay
there and then the planets continue to
migrate in with these exact ratios as
their orbit and you might be like
walking but so what the point is that if
that happened to these planets that
means the planet started here further
away from the star behind the ice line
and then ended up here this would mean
that they formed with a lot of ice and
so maybe as they moved close to the star
this may have melted to become a global
ocean so our other option instead of a
lava world it could be that the Trappist
one planets have a huge amount of water
and they're actually water worlds with
no exposed land at all so this is a
beautiful graphic by NASA and if we go
below the atmosphere this is how we
might picture a water world so this then
brings us to the obvious question on
what a world's habitable I mean water
and life are intricately assetid are
associated on earth so is more water
better for life well the short answer is
we don't know
we've got no analog in our solar system
to go and explore which has a surface
global ocean however we have some reason
to be slightly skeptical and it comes
down to the carbon dioxide in our air so
if we didn't have an atmosphere the
global temperature of the earth would be
minus 5 Celsius below the freezing point
of water however because we have an
atmosphere and it contains these
greenhouse gases we're able to trap
heat effectively and brings our global
temperature to about 15 Celsius and
exactly how warm our planet gets can be
controlled by geology through what we
call the carbon cycle or sometimes the
carbon silicate cycle so here carbon
dioxide in the air dissolves in rain
water comes down as slightly acidic rain
it reacts with the rocks and forms of
solids this gets swept into the ocean
and it eventually gets returned to the
atmosphere through volcanoes now the
process is very slow so it doesn't
really protect us against man-made
increase in greenhouse gases but it does
protect us over slower moving changes
for example in its early years the Sun
would have been much cooler and during
this time the earth should have been too
cold for life but we have evidence that
it wasn't and one of the possibilities
is that this process was able to change
the amount of greenhouse gases in our
atmosphere so if the planet was colder
this reaction with the rocks would have
slowed down because chemical reactions
slowed when it's colder but we still
would have been spitting out carbon
dioxide into the atmosphere so the
amount of greenhouse gas in the
atmosphere would have risen and given us
a thicker thermal blanket and this
allows us to have a lot more time in
which life can develop on earth but in
Eveland so if you have a global ocean
can you have any kind of carbon silicon
cycle so could a Waterworld
actually regulate its temperature if it
couldn't it has two main effects the
first is your habitable zone which I
presented as a broadband shrinks to a
narrow point because the reason ours is
a broadband is that our carbon cycle can
adjust slightly our atmosphere to allow
us to manage in slightly warmer areas
and slightly colder areas if there's no
way of adjusting the thermostat at the
planets the radiation you receive from
your star needs to be bang-on perfect so
you get a very narrow band for that
habitable zone secondly because you
can't buffer against the star increasing
in luminosity you have a much shorter
time for life to be able to develop so
does that mean it's curtains for any
water wells well not necessarily it may
depend on ocean depth for example if the
ocean is shallow enough you can still
have a carbon silicon cycle with the
ocean bottom it's not as good because
the ocean changes temperature much more
slowly than the atmosphere but it's
maybe not impossible if the ocean gets
very deep then the chances are the
pressure of that ocean floor will rise
so much your form Isis and these ices
will completely seal off your rocky core
from your ocean and so it won't be able
to produce any kind of thermostat at all
so this always leaves the question of
can we go and check these planets out
well our closest exoplanet is the one
orbiting Proxima Centauri this is our
nearest star so is our nearest possible
exoplanet and it's 4 light-years away
now our fastest spacecraft is Voyager 1
which is currently at the edge of our
solar system if Voyager 1 was pointing
in the right direction which isn't it
would still take it 75 thousand years to
reach Proxima Centauri B now there are
some other ideas in the pipeline for
instance as project star shots which is
an idea where we could use lasers to
send very very very light spacecraft
great distances reasonably quickly but
it's futuristic technology and we don't
know yet whether it's at all feasible
however all is not lost there are a
couple of really or more a couple
several really exciting missions coming
up that are going to tell us a lot more
about these exoplanets so as the planet
transits across the star surface some of
our Starlight is going to pass through
the planet's atmosphere if we can spot
that then we will see a fingerprint that
marks out the gases at the atmosphere so
the light passes through the atmosphere
particular molecules in the atmosphere
will absorb certain parts of the light
spectrum and so they'll be missing when
we observe them on earth and based on
those missing light waves we can tell
what gases might be in the atmosphere
and this gives us our first hint at
geological processes and maybe even a
whiff of life so obviously in a space
telescope I have to mention that one of
the major instruments that we'll be
looking for this is a course at James
Webb which is due to launch in 2019 but
there's also ESA the European Space
Agency's aerial mission which is
hopefully to go up in 2026 so this is
going to be very exciting and just to
end on an utterly shameless pitch as
Frank mentioned my book comes out today
officially in the u.s. it is full of
truly awful planets I mean there are the
hot Jupiters there are Tatooine worlds
around two stars there are rogue worlds
that have no star at all there are
planets with seas of lava and tar so
really whatever your favorite way to die
horribly is you'll probably find it in
the pages of my book so if you're at all
interested I've put some little cards
here just to remind you please grab one
and thank you very much
questions alright so I'm sure we have a
few questions I see in the green back
there now that was you all these
terrible planets Oh what about ours
which is you know sort of so coddling
almost what is your knee-jerk reaction
when people talk about like a Gaia
hypothesis where it's like a system
working together to maintain this
balance nothing weird yeah
one giant tortoise okay so I'm gonna
repeat the question for the online
audience so the question is what is your
opinion on the Gaia hypothesis that
considers a planet as sort of being an
entire organism and such ways and the
question is where is the bottleneck is
it that life is very hard to start maybe
you never get the planet with the right
organics to start life maybe life
develops but in fact it dies really
quickly or maybe that you can develop
life quite easily and actually it
thrives but it just never becomes
intelligent life because it's not
selected for those sort of options and
one hypothesis put forward by Charlie
lineweaver was actually what he calls
the Gaya bottleneck where he says that
you have to not only form life you have
to form it fast enough that it can
actually change your planet's
environment to self sustain itself and
so that's the idea that in the early
stages of our earth the carbon cycle
that I mentioned before was not
sufficient to actually protect our plan
it's atmosphere and keep it temperate
enough but because we were able to form
life it was able to replace the carpet
obviously the aliens are trying to drown
out her talk and she's revealing too
many secrets folks those of you who've
been here know this has absolutely never
happened before in my 17 years we've
never had that kind of noise let's see
so yes I will also note that we just had
some major work done on the auditorium
honor if you noticed the projectors are
4k and other things and the audio system
was updated a little bit so I apologize
we are this is the first live event to
test out the system in details so you
can see that it is being tested out okay
so back to what you were saying so even
though I obviously external forces tried
to stop me answering this question I
would say that I would consider life as
to be definitely part of the planets I
think when we talk about origins of life
we also have to talk about plant
information and they are intricately
connected yes okay
so the question was on this the seller
type of Trappist one is that what the
route you're asking about yes is a red
dwarf yeah it is a red dwarf but red
dwarfs are interesting they're good why
is it always on my answers as well so
yeah Trappist one red dwarfs have pros
and cons one of the pros is that being
very small and dim stars is much easier
to find planets circling them and indeed
Kepler's successor tests is going to be
focusing on red dwarfs for exactly this
reason however they're also extremely
rambunctious when they're young and they
are prone to a lot of stellar flares and
it is possible that a planets around red
dwarfs may become sterilized because
during this early phase in the Stars
evolution it just might have nuked
everything that might be developing on
the planets at the moment we just don't
know the interesting thing about
Trappist one is if they genuinely did
this migration it might just have saved
them because they would have started
further away from the star when the star
was younger and maybe that it would have
got over its and awkward adolescent
stage by the time the planet started
approaching it all the way in the very
back row there
okay so do you anticipate any technology
that will allow us to see not just
exoplanets but also exomoons I go start
his answer and see if everything cuts
off again yes absolutely so Rene Heller
who is an expert on EXO moon formation
in Germany told me that he feels that
exomoons is where exoplanets was at the
start of the 1990s we are on the brink
and indeed their active search is
currently going on for exomoons
one of them is called HEC which I forgot
what it stands for but it's using Kepler
to look for moons and the P ion that is
David kipping at Columbia University and
currently Kepler is sensitive enough to
find a very very large moon in fact
slightly larger than we believe would
form around a gas giants but could
potentially be captured now of course if
we find that earth sized moons exist
then we have a lot more real estate
because our gas giants are mobbed with
moons
so if you imagine a gas giant in the
habitable zone then it's not habitable
but it might have a whole bunch of moons
that are now it's a slightly interesting
game when you start looking at exomoons
and habitability in particular they get
multiple sources of heat because they
get the star but they also get heat
coming from the planet so that may mean
that if the planet is in the ideal spot
to support liquid water its moons may
potentially be too hot so it might be
your ideal end or or a walk filled moon
would actually left live slightly
outside the habitable zone with the
planet providing that additional source
of heat yeah other questions over here
so what can we learn if we are able to
travel to Mars and explore it
what shall we learn that will enhance
our knowledge on this subject so I think
probably what most people would love to
find is life of any kind where is
everyone but one of the questions might
be does life just never start anywhere I
mean as possible right if we were to
find a second genesis of life that would
probably imply that actually life is
pretty easy to kick-start now Mars isn't
necessarily the best place for that
because it's sufficiently close to the
earth that we can share material indeed
there isn't some theories that it's just
about possible life originated on Mars
and then came across to earth we never
found any evidence for life on Mars so
far and we're maybe more interesting
area might be you so as a moon of
Jupiter it has these deep subsurface
oceans if we were able to find evidence
of life on those I think we could be
more certain to say this was an
independent genesis of life and
therefore life is at least easy to start
if not continue the hot Jupiters
eventually lose our atmosphere by being
so close and why isn't our job here hot
so that the Stars gravitational field
starts to penetrate that atmosphere and
literally starts siphoning it off we
call that a rich Loop overflow and we've
also seen evidence of solar hot Jupiters
rapidly using their answers so certainly
for some of them if they're close enough
yes Jupiter's hot is a big mystery so
the idea of migration was not actually
invented when we found hot Jupiters
indeed the idea have been around since
the 1980s and we knew that it was
possible that this migration process
could occur but we look to our own solar
system didn't see any evidence of strong
migration and therefore it was assumed
either didn't happen or it just wasn't a
major player now we've discovered all
these exoplanets we realize it's a major
sculptor of exoplanet systems so then
the question comes are we weird so what
people think happened with our guest is
is the Jupiter was formed and indeed it
did start migrating and it started to
munch its way towards the inner solar
system which would have not look good
for Earth but as it was doing so
Saturn formed and caught up with it as
it started its own migration and at that
point the gravitational pull of the two
planets together caused a u-turn that we
call the grand tack model after the
sailing turn we turn the boat around so
the two planets moved in together they
actually did a u-turn around about the
position of Mars and moved out and it's
one of the explanations we have for why
Mars is so small because naively we
would have thought further away from the
star where the star's gravity is a
little bit weaker you should actually be
able to build a blog of planets but
instead we have a really squishy one
it's possible that it was Jupiter just
marched right in there
eat up all the building material and
then left now whether this is common we
don't know yet because it's harder to
see planets at Jupiter's distance around
other stars as we start to see more
planets that are further out and get a
more complete picture of planetary
systems I think we'll get a better idea
about whether this grand tack system is
common or whether actually we have a
very unique system question in the
center there and kind of a follow up is
the word migration it indicates that
it's still moving could these could
these hot Jupiters eventually go in
actually hit star that they're there
form
so does this migration process can this
migration process end with the planet
being absorbed by the star
gasps disks and after about ten million
years to starve a prices it at that
point planet migration jutsu the gaseous
stops there is also normally a gap at
the disk edge so the planet could go up
to that gap just before it reaches a
star and also stop because there's no
gas that site so in terms of gas strip
and migration it shouldn't throw the
whole planet into the star there should
be some kind of stopping mechanism now
exactly what stops the planets we're not
certain because we don't see planets all
exactly the same distance which would
suggest it was just stopping at the disk
edge instead we see hot and warm
Jupiter's that obviously seemed to have
migrated but stopped of different
distances and we're still not entirely
sure why that happens there's different
ideas for these plant traps that can
cause for instance sharp density
gradients at the ice line that can slow
a planet down and hold it for a bit and
obviously the gas disc can evaporate at
slightly different times and in job
effectively beaching the planets but for
the hot Jupiters we found now because
the gas disc is no longer when you make
comments or observations about orbits on
distant worlds it seems to me we're
making the assumption that will use a
earth time but a time is relative is it
possible that time is very different on
these different worlds and has a
completely different I don't know if a
second is ten times longer than it is
here or whatever that then for the
impact would be different is there a way
more time to be different actually
experience different but I mean it
doesn't really affect us because we know
all the planets so we see everything
yeah it's we're measuring it from our
point of view so the measurements in
other solar systems is there a minimum
distance from the star and a maximum
distance is that is that kind of area
from on the planet from the star and a
maximum distance is that area where
planets forms of systems is there a
minimum distance from the star or a
maximum distance from a star for planets
so the prototype disc is typically
between one three percent of the mass of
star and for that build-up process from
planets it does not control where the
planets also end up because in addition
to this gas migration which wouldn't
curse them within that disk
there's also specially so if you have
multiple planets in their system they
can gravitationally pinboard each other
out system so in our own solar system we
see evidence for that happening in small
objects so for example some of our
long-range comets come from an area we
call the Oort cloud which is a huge
distance away from us and it's thought
that objects there couldn't possibly
afford that they must afford much closer
where our normal planets are and then
being scattered gravitationally by
planets like Jupiter Saturn in this kind
of gravitational pinball game and when
we look at extrasolar planets we do
sometimes see planets that are far more
distance then there should have been a
decent amount of gas and dust in
existence and we genuinely believe that
that is beyond the edge where we expect
planet formation and they probably
didn't form there but it's a scattering
event lob them further out so as a
result we don't have a hard edge to
where we expect to see a planet not
because we believe it could have formed
infinitely far but just because the
sketching process can learn later
protection of the earth and what we are
doing to it I mean I think it's so all
right so the question was since you're
studying all these thoughts how do you
feel about the protection of our own
planet how we might be treating it I
believe it's a controversial is it got
hold of one of the things I hate so much
with this idea in understand that you
saw a planet so we're not remotely
earth-like once more they want
incredible distances away so much so
that the only way possible are ending
that movie was it go so completely crazy
I think that tells you that even if life
is common in the universe even if there
are no bottlenecks even if the Fermi
paradox is not a thing and you can
develop life on all these worlds we may
never ever reach it and that means as
far as we're concerned we've only got
one earth all right we will see you
again
yeah
