In
the coming weeks, the Planck Collaboration will release the third and
final set of products and papers related to the Cosmic Microwave
Background (CMB) studies derived from the data provided by the
Planck mission of the European Space Agency (ESA). This third
release, together with the two previous ones, constitutes the legacy
of the Planck mission.
The
Planck mission was selected in 1996 as a medium size mission aimed at
obtaining an all-sky image of the CMB anisotropies in temperature and
polarisation with unprecedented sensitivity and angular resolution.
Planck was launched on May 14th
2009 and during four years was collecting very valuable data for the
understanding of the Universe as a whole, and also critical for the
understanding of the properties of the components of our own galaxy
and of other galaxies and their clustering. After just over four
years of a remarkable operation, the mission was turned off on
October 23rd
2013, providing high quality data for which a very large number of
results in the areas of cosmology and astrophysics have been derived.
The results obtained so far, as well as the products in which they
were based on, were made public in 2013 and later in 2015, years
corresponding to the first and full data releases, respectively.
Among the great variety of the results, it is worth pointing out, in
particular, the best determination of the age, composition and shape
of the universe, results that have made the Planck Collaboration
worthy of the 2018 Royal Astronomical Society Award.
The
legacy of Planck has much to do with the knowledge of the physical
properties of the universe. The results published so far establish a
homogeneous and isotropic cosmological model that, with only 6
parameters, is able to truly reproduce the Planck observations of the
primordial and most remote radiation in the universe. In relation to
its composition, it has been possible for the first time to map the
all-sky distribution of dark matter and determine its abundance with
sub-percent precision, and also strongly constrain the alternative
models to the cosmological constant for the dark energy. In addition,
the published results reinforce the existence of an inflationary
period in the very early Universe in which it expanded exponentially
and appeared the quantum seeds that gave rise to the galaxies and
other structures that form what is known as the “cosmic web”.
Another consequence derived from the Planck data is the stringent
upper limit imposed on the neutrino mass that, together with the
lower limit obtained from neutrino experiments, imply a narrow window
of around a tenth of electron-volt (value that, on the other hand,
demands an explanation within the standard model of particle
physics).
The
impact that Planck publications have had on the scientific community
has been very remarkable. The Planck Collaboration, made up of some
200 scientists, has published 136 articles in the journal Astronomy
and Astrophysics with an average of about 200 citations per article.
The Planck collaboration, formed by some 200 scientists, has
published 136 papers so far in the journal Astronomy and Astrophysics
with an average of about 200 citations each. The most cited papers
are the cosmological publications included in the Planck Core Science
Program (focused on the study of the CMB), two of them being the most
cited in physics in the years 2014 and 2016, respectively. In
particular, this has been key to our institute having the highest
impact relative to world of CSIC centres between the years 2012-2014.
In the next and final set of publications and
products that will complete the Planck legacy new and more precise
results will be included. These improved results are a consequence of
a revision in the calibration of data and in the reduction of
systematic effects that prevented the extraction of all the available
information in the polarisation data. On the one hand, this will
imply an even more precise determination of the cosmological
parameters and of the properties of the components of our galaxy. On
the other hand, the new Planck data will be essential to complement
those obtained by the next cosmological experiments that will start
in the next decade, such as the ESA Euclid satellite to be launched
in 2021 and aimed to study the nature and properties of the dark
energy and dark matter through a deep and precise mapping of
galaxies; or KATRIN, which will study the mass and properties of
neutrinos.
Enrique
Martínez-González, head of the Observational Cosmology and
Instrumentation group, participated in the proposal of the mission to
the ESA scientific program in 1993 as well as in the subsequent
activities of instrumental development, data analysis and derivation
of the cosmological results, being Co-investigator of the Planck Low
Frequency Instrument (LFI). He together with the rest of the members
of the cosmology group at IFCA who participate in Planck, who hold
the status of Planck Scientist and belong to the LFI Core Team, have
played a relevant role in the achievement of the important legacy
left by Planck. In relation to the instrumental aspect, the IFCA
group coordinated the project for the development of the back-end
modules of the radiometers of the LFI at 30 and 44 GHz, in close
collaboration with the group at DICOM (UC), and contributed to their
posterior simulation and characterization. In relation to the
scientific exploitation of the data, it has significantly contributed
to the two sets of publications of the Planck Core Science Program
published in 2014 and 2016, respectively, leading three papers in
each set: on the isotropy and statistics of the CMB, on the catalogue
of point sources and on the detection of the integrated Sachs-Wolfe
effect. Also in relation to both sets of publications, temperature
and polarisation maps of the CMB have been produced by means of the
component separation code SEVEM developed by the group, one of the
four official codes of the mission. In addition, the group has led
two papers on the Sunyaev-Zeldovich effect due to the hot gas in the
Virgo cluster and in filaments of the cosmic web, respectively, and
another one on the recently produced multi-frequency catalogue of
non-thermal sources.
