Observing to understanding the Universe
Joseph-Louis Lagrange Laboratory

What are the main research themes of the Joseph-Louis Lagrange Laboratory?

Nicole Nesvadba: The Laboratory focuses on the structuring of matter in the Universe. We have researchers working on samples returned from space missions, material that formed at the beginning of the solar system. Some projects also focus on the study of certain stars, planetary systems, exoplanets, and even galaxies, with studies of structures like the Milky Way.

In addition to these astrophysical projects, we have other related activities. For example, we focus on ground-based optical instrumentation, with a world-renowned interferometry team. Another team works on signal processing and image reconstruction, often using artificial intelligence. Lastly, a fundamental physics team studies fluid mechanics, particularly turbulence phenomena.

High-performance computing skills are at the core of the Joseph-Louis Lagrange Laboratory's capabilities. How do these skills support the observations acquired from large telescopes both on the ground and in space?

For these observations, we work on several aspects, including data processing with very advanced methods, which are not always related to high-performance computing (HPC). In the HPC field, we are involved in the new SKA (Square Kilometre Array) radio telescope. This array of antennas will be invaluable for observing the very early stages of the universe's history, particularly the reionization era, the period during which the first stars formed. We work on the interface between hardware and software, as well as on establishing connections between the Observatory itself and the future users of the local services that will be provided.

We are also highly skilled in preparing software and catalogues from raw data collected during space missions by agencies such as CNES or the European Space Agency (ESA). These data require extensive astrophysical work before they can be used by the international scientific community.

We are also involved in the control and command software for large ground-based telescopes such as the VLT (Very Large Telescope) of the ESO or the ELT (Extremely Large Telescope). The latter is a next-generation telescope currently under construction. With its 39 metre diameter, it will be the largest optical telescope in the world.

The Laboratory’s participation in international projects

The Laboratory plays a key role in the processing and analysis of data from the Euclid and Osiris-Rex missions. What is your involvement in these missions that aim to unravel the mysteries of the Universe?

These two projects seek to unravel the mysteries of the universe on all scales, as they deal with both the very large and the very small. The larger scale is addressed with Euclid, a cosmology mission whose primary goal is to measure the balance between dark energy, which drives the acceleration of the expansion of the universe, and dark matter, which resists it.

Part of these observations focuses on galaxy clusters, which contain vast numbers of galaxies as well as large amounts of gas. Today, we do not know how these enormous masses of extremely hot gas (over a million degrees) formed. Euclid will help us better understand this phenomenon by giving us, for the first time, the opportunity to observe a large number of these clusters, from today back to the early phases of galaxy formation in the universe, around ten or eleven billion years ago.

Osiris-Rex represents the other extreme. It is a U.S. mission aimed at studying an asteroid and bringing a sample of its soil back to Earth. We are the only laboratory in Europe to have received material from this mission. Two of our researchers are now involved in the analysis of the dust that was collected. Here, we are talking about miniature structures that can be observed with microscopes. This primordial dust will provide us with very detailed information on a small scale about the formation of the solar system.

The Lagrange Laboratory is at the head of a European consortium developing MATISSE, an instrument offering spatial resolution equivalent to that of a 150-meter diameter telescope. Where does this programme stand?

Installed in Chile, MATISSE is working very well and producing exciting data. It is an instrument operating in the mid-infrared. It allows us to observe exoplanets as well as planetary systems with planets nearby. With the interferometers we have built at Lagrange, you can also measure the size of certain stars, which helps to better determine their age. MATISSE also enables us, for the first time, to observe the active cores of galaxies—cores that contain supermassive black holes, very strange objects with extremely energetic processes.

The Lagrange Laboratory’s projects in the coming years

We have many projects, unfortunately I cannot mention all of them. One of the major projects for the French astrophysics community involves preparing the instrumentation for the next generation of large telescopes. I have already mentioned the Extremely Large Telescope (ELT) being constructed by ESO. We are involved in the creation of several instruments, starting with the MOSAIC spectrograph, which will allow detailed study of galaxies in extremely distant clusters or stars within the Milky Way.

We are also working on proposing a new method to observe exoplanet systems orbiting stars other than the Sun, with a precision that we can only dream of today. This involves a coronography mode designed to block out the light from the stars, enabling us to better see the light from the planet nearby. Normally, to block the light from the stars, a small screen is used to obstruct the incoming starlight into the instrument, achieving very high definition. However, there is also a very innovative way of using interferometers for this purpose, where the light coming from one telescope nearly cancels out (or cancels) the light from another telescope. The magic behind this is using this phenomenon to make the starlight disappear while leaving the light from the planet intact. This project, called ASGARD, is advancing, and we are currently assembling the instrument in our clean rooms.

In the long term, we aim to get involved in the activities at the ESO (European Southern Observatory) surrounding a new instrument called PCS. This instrument will allow for a better study of exoplanets and their atmospheres, much in the spirit of finding a « second Earth » in the universe.

Do you also have projects in the space sector?

In the space sector, we will participate in several missions, including one by the ESA (European Space Agency) that will rendezvous with the asteroid Apophis, which will approach Earth in 2029. Our researchers will study, among other things, the effects of Earth's tidal forces on this asteroid. Their studies will also help evaluate the best methods to deflect a potentially hazardous asteroid.

We are also involved in the LISA mission, which uses interferometry to detect gravitational waves emitted by the most violent events in the Universe. These gravitational waves provide us with information about black hole mergers. We've already found some initial traces with ground-based instruments, but we aim to better understand their characteristics and the link with the evolution of stars as we know it.