On June 1, 2021, the open source software solution Gammapy was selected by the CTA (Cherenkov telescope array) observatory as a high-level analysis tool (Science Tools) for the reduction and modeling of the data collected by its future network of telescopes being deployed in Chile and the Canary Islands. Gammapy benefited from the participation of some 70 scientists from all over the world with a strong involvement of German and French laboratories, including the Department of Astrophysics at Irfu (Irfu / DAp). Through contributions on analysis methods and data visualization as well as a place on the steering committee, the DAp was able to contribute to this success.
Resulting from a product lineage initiated in 1997 for the developments linked to the VISIR project (VLT Imager and Spectrometer for mid Indra Red), the CEA's cryomechanisms named ICAR (Indexed Cryogenic Actuator for Rotation) will equip the METIS instrument on the largest telescope in the world: the Extremely Large Telescope (ELT) by 2029. For this fifth generation of mechanisms (2004 VISIR, 2010 MIRI, 2012 CAMISTIC, 2017 EUCLID), the IRFU teams had to review the architecture of these mechanisms in order to significantly reduce their manufacturing costs, without degrading their performance (positioning repeatability of 15 µrad peak to peak). The ICAR cryomechanisms have just passed the final design review by a committee of experts from ESO (European Southern Observatory). With this success, the project can now enter the procurement phase for the qualification and series models.
See: video of the design and assembly stages of the prototype over the period 2018-2021
An international team led by several researchers from LFEMI/DAp/CEA has just published a study shedding light on the formation mechanisms of interstellar grains in galaxies. This is one of the key results of the European DustPedia collaboration, which brings together some thirty people from six laboratories: the DAp at CEA-Saclay, the IAS at Orsay, the University of Ghent, the University of Cardiff, the Observatory of Florence and the Observatory of Athens.
Planets that are strongly irradiated by their host stars develop extended atmospheres that can be probed during transits. These atmospheres undergo photoevaporation which can lead to significant changes in the mass and composition of the planets if it continues for several gigayears. These planets are therefore valuable for understanding planetary evolution. The study of the photoevaporation of exoplanets could inform us on the evolution of the atmospheres of the planets of our Solar System whose first atmospheres would have been shaped by this phenomenon. Exoplanets allow us to study this process as it occurs. An international collaboration has studied the HAT-P-32 system (composed of the star of the same name and an exoplanet named HAT-P-32b) by studying two absorption lines: hydrogen and helium. This allowed them to identify remarkable differences between the two lines during the transit, to the surprise of scientists who also thought that hot Jupiters were rather stable to photoevaporation. Although this statement on the long-term stability of hot Jupiters’ atmospheres remains generally true, HAT-P-32b is an exception to this rule and shows that our understanding of planetary evolution remains incomplete!
An international collaboration led by a team from the Astrophysics Department/AIM Laboratory of IRFU has predicted and characterised the expected signature of internal magnetic fields in stars through their seismology - called asteroseismology. This study demonstrates that thanks to the very precise data from the Kepler (NASA), TESS (NASA) and soon PLATO (ESA) satellites, we are potentially able to detect magnetic fields in the cores of red giant stars (which are the descendants of low-mass stars such as our Sun and intermediate masses below ~8 solar masses). The results are published in two papers in the journal Astronomy & Astrophysics.
An international team including researchers from the Astrophysics Department (DAp) of CEA/Irfu, working in particular at the laboratory for the Dynamics of Stars, (Exo) planets and their Environment (LDE3), has been able to demonstrate that stars rotate faster than expected as they get older. Using asteroseismological techniques - the study of stars through the characterization of their oscillation modes by seismic methods - researchers were able to analyze for the first time a complete sample of 91 stars brooding ages 1 to 13 billion years. These data confirm that the oldest stars slow down their rotation less effectively. This discovery sheds new light on the evolution of star rotation and should make it possible to more accurately calculate the age of stars. These results are published in the journal Nature Astronomy on April 22, 2021.
The search for double beta decay without neutrino emission (0νββ) is one of the major challenges of contemporary physics, because its observation would make a clear statement about the nature of the neutrino itself and potentially on the origin of the matter/antimatter asymmetry of our universe. The CUPID collaboration, in which several researchers from IRFU and IN2P3 are involved, is actively researching this process using scintillating bolometers as detectors. In June 2020, the CUPID-Mo demonstrator experiment, which is located at the Modane underground laboratory, demonstrated the excellent potential of this detection method with only 2.264 kg of 100Mo and one year of data collection. In the coming years, the objective of the CUPID collaboration is to design one of the most sensitive experiments ever built by increasing the total mass of 100Mo to 250 kg. Three articles have just been published on the technological and methodological choices needed for this change of scale, while maintaining the required performances of the final experiment.
The ancients understood that heroes, like Orion with Sirius, need their faithful companion. IRFU engineers and physicists and their collaborators are no exception to the rule and have just completed the development of a modern Sirius, a key element of the super spectrometer separator (S3) under construction at GANIL. The tests having been successful and the system has been moved to GANIL for its final installation.
In Greek mythology, Sirius, Orion's faithful four-legged companion, an outstanding hunter, was transformed into a constellation and placed at his side. This famous canid also gave its name to the brightest star in the night sky. IRFU physicists have just honoured him in their own way, this time in the world of detectors.
The 2021 MERAC Prize for the Best Early Career Researcher in Theoretical Astrophysics is awarded to Dr Antoine Strugarek (CEA Saclay, France) for ground- breaking contributions in stellar astrophysics, including dynamo theory, predictions of solar flares and pioneering work on star-exoplanet interactions. The prize from the MERAC foundation (Mobilization for European Research in Astrophysics and Cosmology) is awarded each year by the European Society of Astronomy (ESA).
An X-ray camera, intended to equip the Sino-French SVOM satellite, has just been assembled and delivered by scientists and technicians from the Institute for Research on the Fundamental Laws of the Universe (CEA/Irfu). This high-tech prototype will capture high-energy photons (X-rays) emitted during the explosion of massive stars or the fusion of dense stars. The camera, particularly compact and innovative, integrates in a very limited volume, a complete detection chain, an active thermal control and a filter wheel. It will be placed at the focus of a telescope 1.15 m long to form the MXT (Microchannel X-ray Telescope). With a field of view of 1 square degree, for only 35 kg of mass, the MXT telescope, equipped with an original "faceted" optics inspired by lobster eyes, will make it possible to locate the position of the most powerful cosmic explosions in the Universe with a precision better than 2 arcmin. After various tests, including a calibration campaign in Germany, the assembly will be shipped to China in November 2021 to be integrated into the SVOM satellite, which is scheduled for launch at the end of 2022.
As part of the luminosity increase of the Large Hadron Collider (LHC), the first phase of the ATLAS experiment upgrade is coming to an end, before a restart planned for early 2022. To meet the requirements of physics in a highly radiative environment with a high particle flux, the two internal wheels of the muon spectrometer will be replaced by new devices: the New Small Wheels (NSW).
After several years of R&D and production, IRFU has just sent the last of the 32 detection modules that will be integrated into the NSW at CERN. This corresponds to the assembly of about 400 m2 of gas detectors based on Micromegas technology: a record!
The muon spectrometer of the ATLAS experiment has been an important contribution of IRFU since the design, and IRFU is still in charge of the alignment today. The spectrometer plays a key role in the reconstruction of high-energy muons, the detection of which is crucial for the search of phenomena beyond the Standard Model. The spectrometer consists of about 1200 muon chambers that form a gigantic edifice 44 m long and 24 m in diameter. Despite these imposing proportions, the relative positions of the chambers must be known with an accuracy of the order of 50 μm in order to achieve the optimum performance of the spectrometer. To this end, a network of optical lines is used to continuously monitor the positions of the chambers relative to each other, as well as their deformations. An elaborate procedure for reconstructing the 56,000 parameters determining the alignment (for the central part) has been developed by a team at IRFU in order to obtain the precision required for the reconstruction of high-energy muons. This method, adopted by the ATLAS collaboration, is presented for the first time in an ATLAS note.
The high luminosity phase of the LHC (HL-LHC) should enable the collection of a dataset unprecedented in the history of particle physics. In order to record these data, the Atlas detector will undergo a major upgrade. IRFU, via the Paris-Cluster in synergy with two other laboratories in Ile de France, is committed to the construction of a part of the internal tracker. The year 2021 is brilliantly starting for the Paris-Cluster, which has just passed an important milestone in this endeavour: the first phase of the assembly and testing processes developed by our teams has been validated by the Atlas collaboration.
Nearly 200 researchers were involved in collecting, processing and assembling images of half the sky to prepare for the start of observations by DESI, the Dark Energy Spectroscopic Instrument, which aims to solve the mystery of dark energy.
In order for DESI to begin its 5-year mission (2021-2026) to produce the largest 3D sky map ever made, researchers first needed a gigantic 2D map of the Universe. Based on 200,000 images from 1405 nights of observations on three telescopes and several years of satellite data, this 2D map is the largest ever produced, based on the area of sky covered, the depth of the imagery and the more than one billion images of galaxies it contains.
After three years of reflection and development, the "Astro-Colibri" application has just been launched. This digital interface, created by researchers at Irfu/DPhP, aims to make information on transient and multi-messenger phenomena easily accessible in real time. The need to react quickly to the most violent explosions in the universe and the large amount of information provided by the global network of observatories requires new approaches and new tools. Through "Astro-Colibri", several observatories now have the capacity to coordinate in monitoring and identifying the sources of physical phenomena in the transient sky.
The platform, which exists in the form of a smartphone application (IOS and Android) and a website, allows alerts to be put into their observational context by cross-referencing them with already known data. This saves researchers a considerable amount of time. In addition, the application anticipates the best possible observation periods for a given observatory. This free interface is also a fun and practical tool for astrophysics enthusiasts who will be able to easily move around this functional application.
Space-based experiments such as the Fermi satellite's Large Area (LAT), which detects gamma rays above 100 MeV, reveal a population of sources with no astrophysical counterpart at other wavelengths. Some of these have the characteristics required to be "dark matter subhalo" candidates predicted by cosmological simulations to populate the Milky Way halo. The range of dark matter candidates with masses below a few hundred GeV are already excluded by Fermi observations. To test the higher masses, higher energy range observations are needed and the H.E.S.S. ground-based Cherenkov telescope array is the ideal instrument. Thus, a team of physicists from Irfu and laboratories in Heildelberg and Tübingen conducted a thorough selection of some of the most promising objects to be observed by H.E.S.S. to elucidate their possible identification as 'dark matter subhaloes' at TeV. The H.E.S.S. results exclude this interpretation for dark matter particles in the TeV range. This work was published in the Astrophysical Journal in July 2021 (arxiv link).
On 29 August 2019, scientists from the H.E.S.S. collaboration recorded one of the brightest cosmic explosions ever observed in the Universe. This gamma-ray burst emitted the most energetic photons ever detected in this type of event. Under the direction of Irfu researchers, the observations continued for several days. The analysis of the data collected calls into question the origin of the rays produced during the explosion. These results has been published by the international team, which includes researchers from CEA and CNRS, in the journal Science on 4 June 2021.
H.E.S.S., located in Namibia, is a system of five imaging atmospheric Cherenkov telescopes that has been studying cosmic rays since 2003. In 2016, the cameras of the first four telescopes were completely refurbished using state-of-the-art electronics and in particular the NECTAr readout chip designed by the the DEDIP/Irfu laboratory.
The analysis of this exceptional gamma-ray burst was led by a physicist from the DPHP/Irfu astroparticle group.
Rogue planets are elusive cosmic objects that have masses comparable to the largest planets in our Solar System but do not orbit a star, instead roaming freely on their own. Not many were known until now, but a team of astronomers, using data from facilities across the world, have just discovered at least 70 new rogue planets in our galaxy just a few hundred light-years away in the Scorpion sky region. This is the largest group of rogue planets ever discovered, an important step towards understanding the origins and features of these mysterious galactic nomads.
Imaging planets that could potentially sustain life around nearby stars has become a possibility thanks to advances reported by an international team of astronomers in the journal Nature Communications. Using a newly developed system for mid-infrared exoplanet imaging in combination with a very long observation time, they achieved the capability of directly imaging planets about three times the size of Earth within the habitable zones of nearby stars. This experiment, called NEAR (Near Earths in the AlphaCen Region), was performed using VISIR, a mid-infrared instrument built by the Astrophysical Department of CEA-IRFU. The VISIR camera has been adapted to a 8m large telescope VLT UT4 (Yepun) in Chile, with a specific star-light blocking device and a a built-in adaptive optics sytems to correct for the atmospheric turbulence. A potential Neptune-to Saturn-sized planet orbiting Alpha Centauri may have been pinpointed but still requires further confirmation.
See the video : Breakthrough Watch/NEAR
Since the interferometers of the LIGO-Virgo collaboration detected gravitational waves from the merging of two black holes, black hole binaries have been among the celestial objects that most interrogate scientists. A team of astronomers, including researchers from the Astrophysics Department / AIM Laboratory of CEA Paris-Saclay and the APC laboratory (University of Paris), have determined, using more than 60,000 digital simulations of stellar evolution, the characteristics of the progenitors at the origin of mergers of black hole binaries of mass less than 10 solar masses. According to this study, a phase in the evolution of the binary system known as the common envelope phase plays an essential role in the process eventually leading, or not, to the merger of the two black holes. This work is presented in an article to appear in the journal Astronomy & Astrophysics.
Rogue planets are elusive cosmic objects that have masses comparable to the largest planets in our Solar System but do not orbit a star, instead roaming freely on their own. Not many were known until now, but a team of astronomers, using data from facilities across the world, have just discovered at least 70 new rogue planets in our galaxy just a few hundred light-years away in the Scorpion sky region. This is the largest group of rogue planets ever discovered, an important step towards understanding the origins and features of these mysterious galactic nomads.
Nucleons are social particles. Not only do they enjoy living in communities inside nuclei, but they also form couples within these communities. Indeed, one can observe protons and neutrons forming pairs inside nuclei. DPhN physicists have played a decisive role in the first measurement of such pairs of nucleons using a new method, that will pave the way to the study of these close (or short range) interactions in radioactive nuclei. The results have recently been published in Nature Physics [Pat21]. The study of these nucleon pairs in radioactive nuclei is the goal of the ANR project COCOTIER led by IRFU.
Understanding how the nuclear interaction emerges from the basic constituents of matter is one of the challenges of contemporary physics. The nuclear interaction between nucleons (proton or neutron) is seen as a manifestation of the strong force between quarks, which is mediated by the exchange of gluons and holds the nucleon together. In spite of the longstanding efforts, a unified nuclear interaction that allows predicting the properties of all nuclei does not exist yet.
Two state-of-the-art instruments, GLAD and COCOTIER, were designed and built at Irfu in the last few years and are now operational in the R3B experimental room of the GSI heavy ion accelerator (Darmstadt, Germany). Both are intended to be part of the equipment that will be used at FAIR, the new machine under construction at the GSI site. GLAD is a large acceptance spectrometer for the analysis of relativistic radioactive heavy ion beam reactions. It was installed on site in 2015 and saw the beam for the first time in the fall of 2018. In some experiments, these beams will have interacted upstream on the COCOTIER liquid hydrogen target. The latter, funded in part by the Agence Nationale de la Recherche, has just been used for the first time in an experiment in March 2021. These two pieces of equipment are key elements for measuring the properties of nuclei at the limit of nuclear stability and allow current nuclear models to evolve towards more predictive ones.
