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Satellites, black holes, exoplanets: when science extends beyond our planet

5 episodes
  • 1
    Seeking out life forms on Jupiter’s moons
  • 2
    Are black holes stable?
  • 3
    How do we study the climates of other planets?
  • 4
    Satellites: why are ‘Lagrange points’ so important?
  • 5
    Plasma: a future fuel for satellites 
Épisode 1/5
On June 13th, 2023
6 min reading time
LA MARLE_Olivier
Olivier La Marle
Head of the Universe Sciences programme at CNES

Key takeaways

  • The JUICE mission aims to test the conditions that could have led to the emergence of habitable environments on 3 of Jupiter's 4 frozen moons.
  • To fund it, space agencies must work together, with each country building part of the on-board instrumentation.
  • As part of JUICE, France is responsible for the infrared spectrometer, and has contributed to the development of half a dozen other instruments.
  • One of CNES's research priorities is miniaturisation, as the mass of the payload is one of the main problems in space.
  • Among the results expected from the mission are an understanding of the seismic effects of Jupiter and the icy crust of its moons.
Épisode 2/5
Arthur Touati, PhD Student in Mathematics at École Polytechnique (IP Paris)
On June 1st, 2022
4 min reading time
Arthur Touati 1
Arthur Touati
PhD Student in Mathematics at École Polytechnique (IP Paris)

Key takeaways

  • Black holes began as purely mathematical ideas, unexpected by-products of Albert Einstein's 1915 theory of general relativity.
  • If the density of a body exceeds a certain threshold, it will distort the space around it and become a black hole. For example, for the Earth to be a black hole, it would have to fit inside a pistachio.
  • Recently, two mathematicians have shown that these surprising objects are stable, a first step towards understanding the final state conjecture..
  • It is hoped that new technologies will soon allow us to observe the birth or at least the youth of a black hole in order to better understand them.
Épisode 3/5
Isabelle Dumé, Science journalist
On June 1st, 2022
4 min reading time
François Forget
François Forget
CNRS Research Director in Astrophysics

Key takeaways

  • At the Dynamic Meteorology Laboratory (LMD), researchers are studying the Earth's climate using satellite observations and numerical models to simulate the atmosphere.
  • Their objective is to predict what will happen on our planet in the future as well as on others in our Solar System.
  • For example, they have developed Dynamico, a tool to calculate circulation in Earth's atmosphere – low-pressure areas, anticyclones, and winds – which they have also used to study Mars and Venus.
  • They are also trying to model the climate on Mars from thousands or even billions of years ago to better understand recent ice ages or even the presence of lakes and rivers on its surface from a long time ago.
Épisode 4/5
Paul Ramond, Post-doctoral Fellow in Astrophysics at Université Paris Dauphine-PSL
On June 1st, 2022
5 min reading time
Paul Ramond modifiée
Paul Ramond
Post-doctoral Fellow in Astrophysics at Université Paris Dauphine-PSL

Key takeaways

  • The JWST satellite, launched on 25th December 2021, recently reached its anchor point in orbit around the sun, known as the L2 Lagrange point.
  • Lagrange points are based on a mathematical conundrum known as the ‘three-body problem’, which involves, for example, two celestial bodies orbiting the sun. This orbit is the first Lagrange point.
  • The co-rotating frame of reference, which reduces the satellite’s trajectory to a single point, allows us to find the other two Lagrange points - L2 and L3 - on the same axis.
  • But there are actually more than three Lagrange points. It was Joseph Louis Lagrange who demonstrated that there are five. However, the two other points are not in the same reference frame as the first ones.
Épisode 5/5
On December 6th, 2022
3 min reading time
Pascal Chabert
CNRS Research Director at the Plasma Physics Laboratory (LPP*) and Lecturer at École Polytechnique (IP Paris)

Key takeaways

  • Cold plasmas with a low degree of ionisation can be used for satellite propulsion.
  • To do this, a gas must be ionised to obtain positive ions that are then accelerated, an approach that allows for lower fuel consumption.
  • However, the flux of positive ions exiting the satellite must be neutralised, to avoid an excess of positive charge.
  • The PEGASES project makes use of a plasma containing both positive and negative ions, alternately accelerated in space.
  • The project has identified iodine, as an alternative to the usually employed xenon, as the ideal gas from which to create the propulsion plasma.


Arthur Touati 1

Arthur Touati

PhD Student in Mathematics at École Polytechnique (IP Paris)

Arthur Touati works on high-frequency gravitational waves and is the author of the popular book Voyage Au Coeur De l'Espace-temps (published by First).

Other contributions

Isabelle Dumé

Isabelle Dumé

Science journalist

Isabelle Dumé holds a PhD in physics. She collaborates with various scientific magazines and media, public and private institutions, and actors in higher education and research in France and worldwide.

Paul Ramond modifiée

Paul Ramond

Post-doctoral Fellow in Astrophysics at Université Paris Dauphine-PSL

Paul Ramond’s research topics concern various theoretical aspects of gravitational systems. He works at the CEREMADE laboratory of the University Paris Dauphine PSL on the relativistic mechanics of black holes and Hamiltonian dynamical systems. He conducted his PhD at the UMA laboratory at ENSTA Paris (IP Paris) and at the LUTH of the Paris Observatory.