Un oral d'anglais

The article I have chosen is about the Hubble Space Telescope and the seven exoplanets in orbit around the dwarf star TRAPPIST-1.

In first, what is an exoplanet? It's only a planet outside the solar system. An exoplanet, or extrasolar planet, is a planet orbiting another star than the Sun. Exoplanets are evoked as early as the 16th century, but it wasn't until the 19th that exoplanets became the subject of scientific researches. The distance, but also the lack of luminosity of these celestial objects so small compared to the stars around which they orbit, made their detection impossible. Today it is possible to detect them by means of terrestrial telescopes or space observatories. As of November 2017, more than three hundred exoplanets have been confirmed and several thousand exoplanets are awaiting confirmation. Extrapolating from the discoveries already made, there are at least a thousand billion exoplanets in our galaxy alone.

Exoplanets are a very important research topic because it comes under astrobiology, which is none other than the study of geochemical and biochemical factors and processes, which can lead to the appearance of life and its evolution on our planet and outside. Some exoplanets have a great potential for the appearance of life.

The article focuses precisely on 7 exoplanets, 40 light years from Earth. They are in orbit around the dwarf star TRAPPIST-1 formed about 7.6 billion years ago (UNIVERSE: 14 billion years / EARTH + solar system: 4.5 billion years), discovered by the TRAPPIST telescope in 2015. These exoplanets are approximately the size of the Earth. He explains that a study conducted with the Hubble telescope early 2017 revealed that these planets could still shelter considerable amounts of water. Three of them (TRAPPIST-1 e, TRAPPIST-1 f and TRAPPIST-1 g) are located at a distance from their star that could allow them to harbor liquid water. These three exoplanets could have oceans of liquid water on the surface with an atmosphere similar to that of the Earth.

However, the study also shows that these exoplanets undergo strong irradiation in the ultraviolet and X-ray domains compared to the Earth, which could have significant consequences on the maintenance of their atmosphere and cause by complex phenomena huges losses of water. According to the study, the first three exoplanets b, c, d would have lost the equivalent of 20 terrestrial oceans and the three exoplanets in habitable zone would have lost the equivalent of 4.

More advanced studies should be carried out with the future James-Webb Space Telescope, which is due to be launched by the end of 2018. Their relatively small distance from the Earth makes it possible to study the atmosphere by spectroscopy.

Does life already exist on these planets? Would she have enough time to evolve on one of these worlds? We don't know yet.

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