Space
Science and technology

On June 1st, 2022

4 min reading time

Arthur Touati

PhD Student in Mathematics at École Polytechnique (IP Paris)

- 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.

On June 1st, 2022

4 min reading time

François Forget

CNRS Research Director in Astrophysics

- 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.

On June 1st, 2022

5 min reading time

Paul Ramond

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

- 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.

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)

- 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.