SVOM mission to study the most distant stellar explosions successfully launched

The Franco-Chinese SVOM space mission, dedicated in particular to the detection and study of the most distant explosions or mergers of stars, known as gamma-ray bursts, was successfully launched on June 22, 2024 by the Chinese Long March 2C launcher, from the Xichang launch base in China. Scheduled to last three years, it is the fruit of collaboration between the two national space agencies, the China National Space Administration (CNSA) and the Centre National d’Etudes Spatiales (CNES), with major contributions from CEA and CNRS for France.

Gamma-ray bursts are the most energetic phenomena in the Universe: they result from the most distant explosions of massive stars, but also from the fusion of compact objects such as neutron stars. Lasting just a few thousandths of a second, these flashes are the result of a colossal release of energy, equivalent to that generated by the Sun over its entire lifetime. Some gamma-ray bursts are thought to occur when two neutron stars, or a neutron star and a black hole, orbit each other before coming together and merging. Others are linked to the sudden death of very massive stars in distant galaxies. This light was sometimes emitted when our Universe was less than a billion years old. So, before reaching us, the light from these stars travels many billions of light-years, taking on the imprint of the Universe’s multiple epochs. In other words, studying gamma-ray bursts helps us to better understand the formation of our Universe.

The transient nature of gamma-ray bursts makes them extremely complex to observe. During the explosion, this brief, intense gamma-ray burst is generally followed by X-ray emission and visible light, which can be observed for several days. To detect, locate and study all these phenomena effectively, SVOM (Space-based multi-band astronomical Variable Objects Monitor), has four instruments: two designed and built by China (GRM and VT) and two by France:

• ECLAIRs, a wide-field X-ray and gamma-ray telescope to detect and locate gamma-ray bursts in the X-ray and low-energy gamma-ray bands. This wide-field telescope covers one-sixth of the entire sky. It will detect gamma-ray bursts and provide their position with an accuracy of around ten arcminutes, equivalent to a third of the Moon’s apparent diameter. The ECLAIRs telescope is being developed under CNES project management by French laboratories under the auspices of CEA, CNRS and its partners, notably the Institut de recherche en astrophysique et planétologie (CNES/CNRS/Université Toulouse III – Paul Sabatier), the Institut de recherche sur les lois fondamentales de l’Univers (CEA) and the “Astroparticule et cosmologie” laboratory (CNRS/Université Paris Cité).
• MXT, a telescope sensitive to low-energy X-rays for observing gamma-ray bursts. With its small field of view (57×57 arcminutes), it will detect the afterglow of gamma-ray bursts and provide their position on the celestial vault with an accuracy of better than 30 arcseconds (the apparent diameter of Jupiter) in 50% of cases. It is being developed under CNES project management, in conjunction with CEA and CNRS, notably through the Laboratoire de physique des deux infinis – Irène Joliot-Curie (CNRS/ Université Paris-Saclay) (1). Strasbourg Observatory also contributed to its development, in particular for the telescope’s data processing tool and the simulation benches for scientific pipelines.

In practice, when a gamma-ray burst is detected by ECLAIRs, the satellite will reorient itself in a matter of minutes to aim precisely at the area of the localized event, enabling instruments with a narrow field of view, such as MXT, to observe the burst in turn. Information on the position of the gamma-ray burst on the celestial vault will also be transmitted to the ground in less than a minute, thanks to a network of antennas deployed all around the equator and the tropics, to two watch centers set up in France and China. The latter will then be able to launch further investigations and, if necessary, alert large terrestrial telescopes so that they too can orient themselves towards the area of sky and observe the gamma-ray burst.

To complement the observations made from space, the scientists on the SVOM mission have at their disposal a panoply of terrestrial observation instruments dedicated to the project. One of the key components is the COLIBRI robotic telescope, specially developed for the occasion and the fruit of close collaboration between France (where CNRS, the University of Aix-Marseille and CNES played a key role) and Mexico (UNAM and CONACHyT). This telescope offers unique performance in terms of sensitivity, speed and spectral coverage, making it the only one of its kind in the world. It is this close synergy between ground and space, coupled with the multi-wavelength nature of the observations, that constitutes the great scientific and technical achievement of the SVOM mission.

The SVOM mission, launch, satellite and operations are under Chinese responsibility. Design and production of the instruments and ground components are shared between China and France. CNES is the mission’s program manager and the project’s technical manager, and is the prime contractor for the ECLAIRs and MXT instruments, in partnership with CEA and CNRS laboratories and their partners, who are also responsible for the project’s scientific aspects.

Philippe Baptiste, President and CEO of CNES, comments: “CNES’s essential participation in the SVOM mission, with its two innovative instruments, is further proof of the strength of our international collaboration in making major scientific discoveries. This mission will enable us to collect invaluable data on the most powerful stellar explosions in our Universe, and thus gain a better understanding of its formation.”

Antoine Petit, President and CEO of CNRS, comments: “I would like to congratulate the men and women involved in this mission, and in particular the engineers and researchers in the laboratories of CNRS and its partners, who have worked so hard to ensure its success. The launch of SVOM equips our scientists with an absolutely unprecedented observatory that will be capable of probing the most violent phenomena in the Universe.”

François Jacq, General Administrator of the CEA, comments: “The CEA is very proud to contribute to this space project, bringing its know-how in terms of design, integration and qualification of space instruments, as well as bearing scientific responsibility for the mission on behalf of France. We’re looking forward to receiving and analyzing the first SVOM alerts in the autumn, which will open a new window on the driving force behind the most energetic objects in the universe. It’s also a magnificent example of open science, with data instantly shared with the international scientific community.”

Note

1 Also involved : the Astrophysics Instrumentation and Modeling Laboratory (CNRS/CEA/Université Paris Cité), the Paris Institute of Astrophysics (CNRS/Sorbonne University), the Marseille Astrophysics Laboratory (CNRS/CNES/Aix-Marseille University), Observatoire Astronomique de Strasbourg (CNRS/Université de Strasbourg), Centre de Physique des Particules de Marseille (CNRS/Aix-Marseille Université), Laboratoire Galaxies, étoiles, physique et instrumentation (Observatoire de Paris – PSL/CNRS), Laboratoire Univers et Particules de Montpellier (CNRS/Université de Montpellier).

Further Resources

• « Un satellite à l’affût des sursauts de l’Univers » (CNRS LeJournal)
• SVOM, en quête des sursauts gamma de l’Univers (CNES YouTube channel)
• Et si on regardait mourir les premières étoiles de l’Univers ? (CEA YouTube channel)
• Mission SVOM : les guetteurs du ciel (CEA YouTube channel)
• Launch of the SVOM gamma burst detection satellite: a new chapter opens for astroparticle physics! (AHEAD 2020)

IRAP Contact

• Jean-Luc Atteia, Jean-Luc.Atteia@irap.omp.eu