“CoRoT – The First Transiting Exoplanets from Space” with Magali Deleuil (Aix-Marseille Université & Laboratoire Astrophysique de Marseille, France)

The CoRoT satellite, launched in December 2006, was the first mission designed for the search of exoplanets from space. Well adapted to explore the close-in planet population, it has opened the domain of the super-Earth planets, a population that had not been predicted by planet formation models but was later demonstrated by Kepler to be numerous. CoRoT – the name is an acronym for ‚Convection, Rotation and planetary Transits’ – has also shown the existence of close-in brown dwarfs, resurfacing the question of what distinguishes massive planets from low-mass brown dwarfs and bringing the first observational constraints to models. For giant planets, the contribution of CoRoT has been extremely valuable. Massive planets have been found around host stars that are at odds with the regular solar-type stars on which radial velocity surveys concentrated: fast rotators, active stars and even a case of a planetary system whose host star exhibits pulsations.

In the talk the major scientific achievements of the CoRoT mission in planetary science will be reviewed. It will also be explained how the international collaboration on the Exoplanet program of CoRoT worked and how the mission played the role of a benchmark for the European exoplanet community. It has triggered a new generation of young scientists that became familiar with ultra-high precision photometry and have acquired expertise in it. Searching for – and finding – rocky planets outside our Solar System, CoRoT was a very important stepping stone in the European effort to find habitable, Earth-like planets around other stars.

CoRoT used its telescope to monitor closely the changes in a star’s brightness that comes from a planet crossing in front of it. While it was looking at a star, CoRoT was able to also detect ‘starquakes’, acoustical waves generated deep inside a star that send ripples across a star’s surface, altering its brightness. The exact nature of the ripples allows astronomers to calculate the star’s precise mass, age and chemical composition. This technique is known as asteroseismology and ESA’s Solar and Heliospheric Observatory (SOHO) has been taking similar observations of the Sun for years. The CoRoT data is therefore essential to compare the Sun with other stars.

The payload of the CoRoT satellite consisted of a 27 cm off-axis telescope, the associated camera, and the mechanical structures and electronics. To accommodate the two prime scientific objectives (exoplanet search and asteroseimology of stars) the adopted approach consisted in splitting the focal plane in two parts, each dedicated to one of the mission goal. The CoRoT satellite was sent into a circular polar orbit with an altitude of 896 km and remained operative there until November 2, 2012, when a computer error terminated the mission. Its orbit allowed for continuous observations of two large and opposite regions in the sky for half a year each. Within each region there were many stellar fields that were monitored in turn. The reason for the oppositely sited regions was that – because of the Earth’s movement around the sun – the sun’s rays started to interfere with the observations after 150 days. CoRoT then rotated by 180 degrees and started observing the other region. The mission had a nominal lifetime of 2.5 years, after two mission extensions and six years of science operations the instrument stopped working in November 2012. The mission was led by the French space agency, CNES, in association with French laboratories and with a significant international participation. Austria, Belgium, Germany and ESA (Science Programme and RSSD/ESTEC) contributed to the payload whereas Spain and Brazil contributed to the ground segment.

Magali Deleuil is a senior scientist at the Laboratoire Astrophysique de Marseille (LAM) and a Professor at Aix-Marseille University. She has been head of the Exoplanet team at LAM then co-head of the Planetary System Group team at LAM. After a thesis on spectroscopic analyses of subdwarves, she moved to the field of circumstellar disks. She carried out various studies aimed at determining the physical properties of circumstellar disks around young stars and debris disks, such as the Beta Pictoris one. In 1996, she enlarged her scientific interests to detection and characterization of exoplanets by the transit and radial velocity methods. Magali Deleuil was and is involved in the preparation and exploitation of various space-based exoplanet missions: She has lead the international CoRoT/Exoplanet collaboration and is the coordinator of the French participation to PLATO. In the latter, she is a member of the Science Working Team appointed by ESA and of the Board with the responsibility of some high level workpackages in both the PLATO Data Processing Center and the PLATO Scientific Preparation. Magali Deleuil is also very engaged in teaching, covering topics ranging from mathematics, computer science, physics, to astronomy and astrophysics. She also developed a MOOC (Massive Open Online Course).

Seminar was recorded on December 3, 2020