[Music]
there is one thing I believe to which I do not
I will never get used to life and that is it
people’s look when I tell you
that I deal with astrophysical astrophysics
I tried a comparison to make people understand
what it means nowadays to be
an astrophysicist and the first thing that is me
come to mind is a bit be a
explorer for this that I took
on loan the title of the intervention of
today from a famous film by the Indian
jones the raiders of the lost ark e
I have a little reinterpret or calling it
the predators of the photon lost because
precisely the protagonist of this
intervention today is not me but the
the true protagonist is precisely the photon
now maybe many of you are not gods
experts do not know what a photon is
a photon is practically a quantum of
light from the Greek word photon
it really means light was therefore the
light that we see visible light to one
sure its energy is quite low
we say we use a term
technical to define the energy of a
photon that the electronvolt in short the
light that we see the use of light bulbs a
visible light and some electron volts
so a very low thing now though
what I would like to talk to you about today
it is visible light but it is a radiation
very different much more energetic
then these energy packages
these are much more energetic
and they are the gamma photons of radiation
range
now I believe that in the common imagination
when you hear about radiation
range you think almost always to hulk a
be monstrous that was indeed
transformed because it has been exposed
the gamma radiation is now excellent
compare this too also for say
on a scientific level because where
these are produced
gamma radiation
in the universe it is produced precisely
where there are more springs
more violent catastrophes more
monstrous therefore from there we can say
which is definitely a good comparison now
but how is it that we ourselves are not there
we transform each day into hit hulks
from this gamma radiation and we have
a natural protection that protects us
every day or our atmosphere
we are protected by ours
atmosphere what they did then i
astrophysical physicists to say how I can
study this gamma radiation have
decided to go beyond the atmosphere today
we talked about clouds
here we go with other instruments
beyond the clouds beyond the atmosphere and there
we move into space this is
an image of the nasa satellite for which
precisely, I too am a nasa project
in collaboration with the agencies
German and Italian space companies
Swedish Japanese that is in orbit
around the earth at around 550
kilometers of height and orbit around
to the earth about an hour and a half
constantly and precisely it is ours
satellite to be able to capture in order to be able to
go hunting for these of these
fotoni is now in orbit since 2008
next year we will celebrate ten years
since the launch of this satellite in ten
we have seen many years of photons
in april we had a kind
let’s say anniversary because we have
revealed the billionth photon here
let’s say they are really big like
numbers but how is it that we communicate
precisely with this satellite
clearly we take the data
we receive on the ground
But we really say in the life of
every day the best way to
communicate with this satellite are
just our cell phones
obviously we have programs
you were on the cell phone that allow us
to receive just classic text messages
ms ms me one or a few has arrived
minutes ago
who told me the satellite recorded
let’s say a bit of photons that are
arrived all together
here is this event we call it a
gamma-ray burst when one arrives
set of photons all in the same
moment and in a very short time
think that what has arrived few
minutes ago in an event so short
that did not last two seconds
that is, just two seconds is a time
really ridiculous
how much energy we have measured with
this tool that is
built specifically to capture and
let’s say let’s interact the photon
inside and measure the energy well
in a second and a half we have
recorded an energy equal to that
that the sun emits throughout his life
throughout its life cycle
so imagine what we are
talking about this flash of rays
just short range we could
measure energy but demand
classic now is where it comes from
where does it come from what is it?
well then we take a trip to
backward we try to understand from where
this comes when these photons revered
of extreme energy
now to understand how to go
say around the space you need a
moment to understand the distances and the
timing
if you think that when we look for
example of sunlight
we are practically looking at one
sort of image taken some
minute before now we respect ours
we are only about 150 million
kilometers so to get a vague idea
and the light that has a finite speed
so the photon of light puts us 8
minutes to get up to us
this means that when we
let’s look at the sunlight in reality
let’s see the light that started 8 minutes
it does the same way when ours
satellite records a gamma photon taken
at the point the range that arrives
probably from very far and then
He left a long time ago
how much
long ago and this is what we are looking for
to go then to explain then surely
it did not come from our system
solar
so we have to talk about distances
huge and definitely not even
come from our galaxy our
galaxy is nothing but a whole
let’s say of so many solar systems
stars like our biggest sun
there are really smaller ones
many have arrived at this point
we must find another unit
measure to explain how much they are
great these distances
think that the galaxy is 100 thousand wide
light years the light year is precisely unity
of measure to say to describe one
distance that is a distance traveled
from light in a year then
Imagine how many thousands of
billions of kilometers
we are talking here are these photons of
I spoke to you of this flash of light
But it does not even come from here we have to
move therefore not to 100 thousand years
light but not even millions of light years
we have to get to billions of years
light to a few billion means that the
light that we have just registered
It started a few billion years ago and
so it is and what’s in this place
distant
something like that probably happened
an event happened as I hate you
tarot monstrous catastrophic thing
see here you see two objects we could
say two stars you are probably
they are two stars of the universe there are
many stars of various da.dd
dimensions and often do not lie like
our sun that is a star
lonely a single star
no are often found in pairs around the
50 percent of the star systems
they are binary systems
here this is a system case
binary that we suddenly say with
leader like never these two stars in
particular that are said to be depicted
here
artistically they are two stars that are
somehow a little comparable to the
our sun because as dimensions
we say as mass as mass
enclosed in this star are
comparable, maybe they are as big as they are
a two solar masses, however, imagine yourself
to take the mass of the sun that is
a million and a half kilometers away
so it’s huge and put all this
mass in the size of a few tens
of kilometers as if you put the
size the whole mass of ours
sun inside the diameter of the city of
taranto for example here is to imagine
how dense these stars are they are
a density such that it is practically
a density comparable to the atom la
atomic density and for these come
call neutron stars
now what happens these stars
practically they begin a sort of
dance for which orbit one next to one
close to each other are linked by
gravity and start rotating in practice
sis takes place what can be
defined as a cosmic dance there are
these forces between the two stars that
they attract more and more with
the increase we say with decreasing of the
of the distances the two the two stars
they become faster and faster
rotation speed is always more
strong
until the two stars collide
when they collide, what happens is formed
another star another object that is
even more dense than the previous ones
it could be a black hole maybe
some of you have already heard of it
speak
a star that even more dense and
so dense that it also captures light
same from there precisely the name black hole
what you may not have noticed
because the video was very much
fast is that at some point during
this collision was there
the expulsion as of two jets of
matter
here is when these two stars
compact collide both they are
as some of the mechanisms we are still doing
studying and trying to understand why
amat is a part of the matter of
these two stars is expelled in
something good or bad reminds us
a little light, for example the light of the
do not have a lantern and then this
dance that from which we have just
assisted creates these cosmic lanterns
so what did we do on ours?
satellite
we were listening and we were there
affected by one of these events from
somewhere in the universe billions of
kilometers there was an event of the
genre in which these two stars are
merged and sent this impulse that
we remember there was a very brief impulse
I told you a second and we were
precisely ready to capture it
from there a little more the expression
of the explorer that captures the photon
here I would like to end with a with a
another type of signal that could also
let’s be compared to this one
We were celebrating another one
important anniversary in the community
scientific scientific or two years
from the revelation of another kind of
signal not an electromagnetic signal
just like photons but a signal
gravitational wave and gravitational wave
what was born of this wave
gravitational was born from just one
cosmic ballet let’s say a bit like
what you saw in the video
previous were the objects of
departure were larger had one
higher density were probably
black holes that have fused
and they do not however say how in this
case sent a jet a lantern but
they sent a sort of vibration
in the space we have been
able to detect on earth with
of extremely difficult techniques
just to let you understand how much it is
difficult to detect a space signal
storm of that kind you can
imagine yourself being in a lake of
very large mountain with
a very smooth surface and someone
on the other side on the shore
completely opposite throws in water a
tiny pebble and you who are
everything on the other side you have to look for
understand to perceive as on
surface is said to be protracted
this this signal is therefore a thing
very difficult but for the day
today we can do so for
to conclude are so many years now that
say about thirty years that we
scientists we have succeeded in fact
always be on the alert to understand from
where these signals arrive
photons and it’s just been a couple of years
that we are not only alerted we say
visual but we are also listening for
hear these gravitational signals
so at the end of this trip the
what I would like to tell you is
that we explorers us astrophysicists
we are always always listening to each
day we are always on the alert for
capture these signals that when
come to us for billions of years of
distance teach us something about
laws that create our universe
[Applause]
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