Large ground-based telescopes with mirrors over 8 m in diameter1 use azimuthal mounts to point the stars. When tracking a star, the Earth's rotation causes the observed field on the astrophysics detector to rotate, creating "spun" images. To correct this effect, the instruments mounted on these telescopes use a "field derotator", a mechanism whose main function is to rotate a set of mirrors at very low speed and with very high precision. For the METIS instrument, CEA-Irfu has developed one of the world's very first2 derotators operating at -210°C. Entirely designed, developed and tested by the Irfu Systems Engineering Department, the METIS derotator drive achieves performance beyond the expected specifications. Currently in the testing phase, its qualification will be completed by the end of 2023 at ESO in Garching, Germany.
While the use of field derotation mechanisms is relatively common in ground-based astrophysics instruments, most scientific communities choose to place this mechanism upstream of the cryogenic instrument, so that it operates at ambient temperature. Doing this way, the required levels of accuracy (of the order of a few thousandths of a degree) are achieved using 'standard' components such as motorised stages, optical encoders, ball bearings and lubricated gearboxes.
To reduce the instrumental background noise, the METIS instrument of the future ELT will be entirely cooled down to temperatures around -210°C, so the field derotation mechanism will also have to operate at these temperatures in vacuum.
Fermi-LAT telescope continues systematic γ-ray survey
NASA's Fermi satellite was launched in June 2008, and the Fermi-LAT telescope has been carrying out a systematic γ-ray survey of near-GeV energies covering most of the sky every 3 hours (and the whole sky in no more than a week) since August 2008.
The commissioning of the 11.7 T Iseult MRI in 2021 crowned almost 20 years of AOC research and development. In an article published in the journal Magnetic Resonance Materials in Physics, Biology and Medicine, Nicolas Boulant and Lionel Quettier, Iseult project leaders for the CEA's Joliot and Irfu Institutes, review the details of this commissioning.
For the 17th edition of the Prix Jeunes Talents France, the L'Oréal Foundation rewarded 35 brilliant young female researchers in France, selected from 618 eligible applications by a jury of excellence comprising 32 researchers from the French Academy of Sciences. At Irfu's Astrophysics Department, Achrène Dyrek received the award for physics.
Achrène Dyrek has just obtained her PhD in astrophysics. She began her thesis in 2020 at CEA's Department of Astrophysics (DAp), under the supervision of Pierre-Olivier Lagage. During this time, she dedicated herself to the study of planetary atmospheres as seen by the James Webb Space Telescope (JWST - NASA/ESA/CSA), using the MIRI (Mid-InfraRed Instrument) developed at DAp.
Using the James Webb Space Telescope, a group of astronomers led by MPIA, in collaboration with a team from the Astrophysics Department of CEA Paris-Saclay, searched for an atmosphere on the rocky exoplanet TRAPPIST-1 c. Although the planet is almost identical to Venus in terms of size and mass, its atmosphere turned out to be very different. By analyzing the heat emitted by the planet, they concluded that it may have only a tenuous atmosphere containing a minimum of carbon dioxide. However, this is also consistent with a barren rocky planet devoid of any significant atmosphere. This work gives us a better understanding of how the atmospheres of rocky planets orbiting low-mass stars can withstand strong stellar winds and intense UV radiation.
The results are presented in the journal Nature:
On October 9, 2022, at 13:16 and 59.99 seconds, a gamma-ray burst (GRB) dazzled almost all the X-ray and gamma ray detectors available at the time. Since their discovery, multi-wavelength telescopes in space and on the ground have continuously monitored these events. This outburst, named GRB221009A, shook the world community of astrophysicists, who have since been analysing it to understand the physical phenomena that triggered this most intense burst of energy in our history.
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X-rays detection due to the scattering of light from the initial explosion of GRB 221009A by the dust of our galaxy, has led to the formation of expanding rings. This "movie" (in arbitrary colors) shows these rings formed by X-rays detected by NASA's Swift telescope. It was created by combining images captured over a 12-day period. Credit A. Beardmore, University of Leicester, NASA, Switf |
Discovered in 2009, exoplanet GJ1214b orbits a small star just 40 light-years away. With a mass around six times that of Earth and an atmosphere made up of hydrogen and helium, it is considered a "mini-Neptune".
A team from NASA, in collaboration with researchers from CEA Paris-Saclay, pointed the JWST at the planet using the MIRI instrument, built by CEA Paris-Saclay, for some 40 hours. This unprecedented observation made it possible to obtain, for the first time, the phase curve of an exoplanet with MIRI, i.e. complete tracking of the planet's rotation around its star.
By following the evolution of the exoplanet-star system's emission, the research team was able to determine the planet's temperature to within 9°: 280°C on the dayside and 164°C on the night side. Comparing the observations with atmospheric models, the researchers deduce that: 1. the small temperature difference between the two sides, despite the planet's synchronous rotation, means that there is a good exchange of energy between the sides, due to a dense atmosphere. 2. The relatively low temperature on the dayside, given the planet's proximity to its star, indicates that a layer of aerosols in the exoplanet’s upper atmosphere reflects much of the stellar radiation. The type of aerosol with such a property has yet to be determined. 3. The atmosphere contains many elements heavier than hydrogen and helium, probably abundant water.
The results are published in the prestigious journal Nature
An international team of researchers has used NASA's James Webb Space Telescope to measure the temperature of the rocky exoplanet TRAPPIST-1 b. This is the world's first detection of thermal emission from a rocky exoplanet as small and “cool” as the rocky planets in our own solar system. TRAPPIST-1 b receives about twice the amount of energy as Venus receives from the Sun and four times more than Earth. The result indicates that the dayside of the planet has a temperature of about 227°C (500 K) and suggests that it has no significant atmosphere. The study, co-authored by three researchers from the Dap, has just been published in the journal Nature, on Monday 27 March.
On October 9, 2022, at 13:16 and 59.99 seconds, a gamma-ray burst (GRB) dazzled almost all the X-ray and gamma ray detectors available at the time. Since their discovery, multi-wavelength telescopes in space and on the ground have continuously monitored these events. This outburst, named GRB221009A, shook the world community of astrophysicists, who have since been analysing it to understand the physical phenomena that triggered this most intense burst of energy in our history.
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X-rays detection due to the scattering of light from the initial explosion of GRB 221009A by the dust of our galaxy, has led to the formation of expanding rings. This "movie" (in arbitrary colors) shows these rings formed by X-rays detected by NASA's Swift telescope. It was created by combining images captured over a 12-day period. Credit A. Beardmore, University of Leicester, NASA, Switf |
CEA has delivered to CNES the flight version of the ECLAIRs instrument software for the SVOM satellite. This concludes a major instrumental development phase conducted by CEA over a period of 6 years to produce what is maybe one of the most complex software packages ever carried on a French scientific space instrument. The latest version of the software equips the ECLAIRs onboard computer, which departed to China in early 2023. It will be used during the satellite integration tests in Shanghai in preparation for the launch planned for early 2024. This software will analyse in real time the data from the instrument in flight, in order to detect gamma-ray bursts and localise them to better than 12 arcmin on the sky, to reorient automatically the satellite for follow-up observations, and to alert the scientific community.
ESA has selected the THESEUS (Transient High Energy Sky and Early Universe Surveyor) mission as a medium-sized mission candidate. THESEUS is the natural successor to the Sino-French SVOM (Space based astronomical Variable Object Monitor) mission, which will be launched early 2024 (for 5 years of operation) and in which IRFU is also playing a leading role.
THESEUS has been chosen from among 27 missions, along with Plasma Observatory (study of the Earth's magnetosphere) and M-MATISSE (study of the atmosphere and magnetosphere of Mars), for a preliminary study lasting three years (2024-2026), at the end of which one of the three missions will be carried out for launch in 2037.
CEA/IRFU will play a leading role in the mission, as the PI of the international consortium (which includes INAF and Politecnico Milano in Italy, University of Geneva in Switzerland, and LAM Marseille and IJClab Orsay in France) responsible for developing and delivering one of the three satellite's instruments: the IRT (Infra-Red Telescope) and more specifically the camera placed at its focus.
The ATLAS collaboration announced at the Moriond conference the observation of simultaneous production of four top quarks. This is one of the rarest and heaviest processes ever observed at the Large Hadron Collider (LHC). This measurement, coordinated by IRFU, allows to test the Standard Model of particle physics in its most complex predictions.
Reactor antineutrino anomalies are a decade-long puzzle in neutrino physics. They are manifested by deviations of the order of a few percent between measurements and predictions. These deviations have been observed in the number of antineutrinos measured by more than a dozen experiments at nuclear reactors, and in the shape of the kinetic energy distributions by the seven most recent ones. They could have been the way to a new physics beyond the standard model, but the recent experiments, including the STEREO experiment carried by IRFU, have closed this door.
In a work just published in Physical Review Letter [1], a team of physicists from IRFU and the Laboratoire National Henri Becquerel of DRT have shown that these anomalies could come from biases in the measurements of fission electrons used as a reference for the prediction. They have developed a beta strength function model to reduce the biases in the calculation of the energy spectra of electrons from fission of fissile reactor nuclei. The two "anomalies" on the antineutrino flux and the "bump" at 5 MeV in the antineutrino energy spectrum are now reproduced by their model. This allows to propose an explanation to solve an enigma of more than 10 years.
On October 9, 2022, at 13:16 and 59.99 seconds, a gamma-ray burst (GRB) dazzled almost all the X-ray and gamma ray detectors available at the time. Since their discovery, multi-wavelength telescopes in space and on the ground have continuously monitored these events. This outburst, named GRB221009A, shook the world community of astrophysicists, who have since been analysing it to understand the physical phenomena that triggered this most intense burst of energy in our history.
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X-rays detection due to the scattering of light from the initial explosion of GRB 221009A by the dust of our galaxy, has led to the formation of expanding rings. This "movie" (in arbitrary colors) shows these rings formed by X-rays detected by NASA's Swift telescope. It was created by combining images captured over a 12-day period. Credit A. Beardmore, University of Leicester, NASA, Switf |
On October 9, 2022, at 13:16 and 59.99 seconds, a gamma-ray burst (GRB) dazzled almost all the X-ray and gamma ray detectors available at the time. Since their discovery, multi-wavelength telescopes in space and on the ground have continuously monitored these events. This outburst, named GRB221009A, shook the world community of astrophysicists, who have since been analysing it to understand the physical phenomena that triggered this most intense burst of energy in our history.
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X-rays detection due to the scattering of light from the initial explosion of GRB 221009A by the dust of our galaxy, has led to the formation of expanding rings. This "movie" (in arbitrary colors) shows these rings formed by X-rays detected by NASA's Swift telescope. It was created by combining images captured over a 12-day period. Credit A. Beardmore, University of Leicester, NASA, Switf |
The European Research Council has just announced the names of the winners of the Advanced Grant. This 2023 edition rewards in particular two researchers from the CEA's fundamental research department for their work in the fields of astrophysics and neuroscience. Anaëlle Maury is the leader of the PEBBLES project. This project consists of developing an innovative methodology to characterise the properties of dust around very young stars in the process of forming their proto-planetary disks. Dust is one of the key elements in the physical processes regulating the formation of stars and their planetary systems, but recent observations are overturning the models used until now to describe its evolution from submicron grains to pebbles. Observing and modelling the properties of dust grains during the earliest phases of disk formation promises to provide important insights into the conditions leading to the formation of solar systems such as our own. Through PEBBLES, the teams will use new dust models that are better suited to denser astrophysical environments and will use them in comparison with observations from space missions and ground-based observatories from the infrared to the millimetre range.
