IAC INVESTIGATES
COSMOLOGY AND ASTROPARTICLE PHYSICS
The universe is everything around us:
the stars, the galaxies, intergalactic space...
Now we know that the universe
is finite, it has an age;
it began 13,800 million years ago.
We know that the universe is really quite uniform
and homogeneous on large scales.
The universe is expanding. In fact,
it is expanding more and more rapidly.
The energy and matter content
of the universe changes with time.
Among the most important ingredients
are dark matter and dark energy.
Some 95% of the matter and energy in the universe
are in forms which we still don’t know about.
By studying the universe we can understand
how it was born, how it is structured,
what it is made of and
how it will evolve in the future.
I think that these are questions
to which humanity expects answers.
For this reason alone it is important
to understand and study the universe as a whole.
THE ORIGIN OF THE UNIVERSE
If we run the film of time backwards we would find
that in the past the universe was increasingly dense and hot
and we can extrapolate that to the first instant,
which would be the Big Bang.
The Big Bang was really a very rapid expansion.
The Cosmic Microwave Background (CMB) is
the “fossilized” proof that the Big Bang existed.
This is the radiation which remains in the present day universe,
and which was present during its first moments.
The CMB is definitely the oldest radiation we can observe.
It is present in each cubic centimetre of space.
It is very uniform, but it is not absolutely uniform.
It has small variations which cosmologists
have termed “anisotropies”.
It is very important to study these anisotropies
because they connect us with the original structures
which seeded all the structures in the present day universe.
However, the simple theory of the Big Bang is not complete.
It needs an addition, which is the theory of inflation.
Inflation refers to an extremely fast expansion
during the first instants of the universe.
As with all energetic phenomena it should
have produced what we know as gravitational waves.
The primordial background of gravitational waves
should have imprinted a specific pattern on the CMB.
This tracer, known as “B modes”, would give us
indirect evidence that inflation really took place.
STUDYING THE EARLY UNIVERSE
In the IAC, Cosmology has been developed
for a little over 30 years.
Beginning in 1985 with the Tenerife experiment,
followed by many others until today
when we have the QUIJOTE experiment.
This aims at measuring the traces of gravitational waves produced
during the first instants of the universe by detecting the B modes.
The QUIJOTE project comprises two large telescopes
of some three metres in diameter.
These telescopes will be equipped with three instruments,
three sets of detectors which can observe in three different
frequency ranges, in particular in the microwave range.
No other present day cosmological instruments
are observing in this range.
The challenge of the QUIJOTE experiment has not only
been in the design, but also in its construction,
which has entailed making and
mounting very complex parts,
as well as reaching the required
operating temperature
below -250 Celsius degrees.
This temperature is only slightly above the absolute zero,
which is very difficult to achieve.
QUIJOTE  is a very ambitious project because
it aims at finding a morsel of clarity in our understanding
of the origin of the universe and
of all its contents, including ourselves.
In the IAC we have also developed
technology for cosmological space missions.
The Planck mission of the European Space Agency (ESA)
had IAC participation.
For the future the IAC is involved in the Euclid mission,
which is a new ESA satellite whose
objective is to characterize dark energy.
ASTROPARTICLE PHYSICS
Within astrophysics there is a new, recently
started field, that of astroparticles.
In astroparticle physics we want to unify
the physics of particles with astrophysics.
And it uses different types of particles
as messengers from distant cosmic objects.
Right now, and always, we are being bombarded by a huge quantity
of charged particles which are always passing through us.
The importance of these particles is not that they are just around,
but because they have been accelerated somewhere.
So that they reach us with such high energy.
For particles to be accelerated to such
high energies we need extreme conditions
for example a black hole, the explosion of a supernova,
or an active galactic nucleus.
In other words, there is an enormous amount
of energy associated with these particles
and we need to know where this energy is generated.
The ultra-high energy universe is very different from the universe
which we see in other bands of the electromagnetic spectrum.
Everything we observe in this range is associated with
the most energetic, the most violent processes,
which in general means that it is associated
with processes which are very distant from us.
This means that we can see deeper into
the cosmos that at most other wavelengths.
By studying particle physics we can
go back to the origins of the universe.
We can study the universe when it was forming.
The most important objectives for astroparticle physics are
the study of dark matter and of the extragalactic background radiation.
We hope to be able to help cosmologists during
the coming years by developing these fields of study.
High energy astrophysics is the window we needed to open.
STUDYING HIGH ENERGIES
Every type of cosmic messenger
needs its own type of detector.
The detection can be made
in space or on the ground.
For example to detect ultra-high energy
gamma rays we use detectors on the ground.
What we do is to observe what happens
when the particles hit the Earth atmosphere.
What happens is that a gamma-ray photon
interacts with particles in the upper atmosphere
and produces subatomic particles,
which we call an electromagnetic shower.
Some of these particles have speeds
higher than the speed of light in air.
This produces radiation, “Cherenkov radiation”
which is blue light produced in very brief flashed
How brief? A thousand millionth of a second.
That is why we need telescopes with very large mirrors to reflect
and measure this tiny light source which lasts for very brief instants.
From this light which we detect on the ground, we can determine
the type of photon, its energy, and the direction it came from.
Historically speaking, high energy astrophysics in Europe essentially
started here at the Roque de los Muchachos Observatory (ORM)
because it was here that the first generation of high energy
telescopes, the HEGRA collaboration, was installed.
And from 10 years ago we also have those telescopes,
the MAGIC telescopes,
which is a pair of telescopes giving rise
to the biggest quantity of information in this field.
The MAGIC experiment comprises two Cherenkov telescopes.
So that we can work in stereoscopic mode since the two telescopes
can observe simultaneously in the direction under study.
The future of high-energy gamma-ray astronomy is CTA,
the new network of Cherenkov telescopes
which will be built in the coming years.
We are over 1.000 researchers
in 31 countries on 5 continents,
and we are all working together
to build a world-wide observatory.
In the IAC we have also participated
for over 10 years in the AMS experiment.
This is a particle detector with the great advantage
of being sited in space on the International Space Station.
CHALLENGES FOR THE FUTURE
In cosmology the final frontier may be “time zero",
an instant which we will certainly never reach.
Studying the first instant of the universe opens doors
to research into basic challenges of contemporary physics.
The nearer we get to “time zero” the higher
is the energy associated with the phenomena
which took place in the primordial fireball.
These energy scales link us directly to fundamental physics,
and specifically to the physics of
the grand unification of the forces of nature.
We still do not have a "theory of everything" which unifies
the theory of gravity with the rest of the fundamental interactions.
A unified theory of the fundamental forces may open
the door to new ways of generating energy
under human control which could be
well beyond present scales
I think that the most enjoyable
aspect is the search itself,
trying to understand how things work,
giving explanations.
It is very interesting to be able to explain what
doesn’t work and to be able to discover more and more.
This is a path which is hard to predict,
and which we are beginning to follow,
using the universe as a macroscopic laboratory
which gives us clues about how to find the answers.
