Origin of the Moon

How was the Moon formed? Anthony Gibert

Several hypotheses have been envisaged by astronomers: formation at the same time as the Earth, captured asteroid, etc. Today, the most accepted scenario is based on a giant impact. At the very beginning of the constitution of the solar system (a little more than 4 billion years ago), an object the size of Mars is said to have crashed into the Earth. This massive shock would have ejected vast quantities of matter from our planet which would have combined to form the Moon. According to the different versions, the impactor would have been pulverised by the collision and the debris (at least part of it) would then have taken part in the constitution of our natural satellite.

To become an astronaut

As a space enthusiast, I would like to know what course you have to take to become an astronaut. It’s my dream! Nils Olsen

One important prerequisite: There are no specific courses that lead to an astronaut qualification. Space agencies recruit personnel according to multiple criteria which include the quality of their studies and their motivation. It is basically sufficient to be excellent within your professional field, not forgetting a strong team spirit and a positive mental attitude. Contrary to any preconceived ideas, you do not have to be an army or test pilot. An advanced level of technical and scientific studies make it possible to be a candidate who could one day attract the attention of your country’s space agency (for example, you have to have American nationality to apply to NASA or be a citizen of one of the European Space Agency member countries to apply to the ESA).
We recommend the following links for further information on the subject:

An excellent CNES Junior feature (in French)

Astronaut requirements (NASA)

Astronaut selection (NASA)

How to become an astronaut (ESA)

EnjoySpaceTV interviews of 4 of the new european astronauts.

A new generation of European astronauts
envoyé par EnjoySpaceTV. - Vidéos des dernières découvertes scientifiques.

Stars and satellites

I would like to know how to differentiate stars from satellites when looking at the night sky through binoculars? Michel Castillon

The basic rule is quite simple: a star moving rapidly in relation to the others (that is to say which crosses the sky in a few minutes) has every chance of being a satellite. “Shooting stars”, which are in fact meteorites, are much more fleeting (several seconds at the most). Obviously, there is always a risk of confusing the passage of a satellite with that of an airplane, but the latter have navigation lights that can be seen with the naked eye or through binoculars, whereas satellites actually give the impression of being a star wandering through the canopy of heaven. The Heavens Above website makes it possible to know when satellites and the International Space Station will be passing through the sky above you.