Conception de documents L3 Utilisez au mieux le contenu de ce texte, et la vidéo derrière le lien http://webbtelescope.org/video/859/science, pour rédiger un article simple et clair, destiné à de jeunes lecteurs français intéressés par la science. Précisez l âge de vos lecteurs (entre 10 et 14 ans), ainsi que le support choisi : Science et Vie Junior, Science Illustrée, ou tout autre support adapté. Calibre : une à deux pages du magazine, selon format. Précisez la mise en page de votre article. NASA Just Discovered Seven New Exoplanets... So What? Forbes/Science / 2 26 2017 / Hilary Brueck Contributor On Wednesday, the scientists at NASA kind of freaked out. They announced the discovery of some seemingly Earth-like planets outside of our solar system, a group of rocky globes they re calling TRAPPIST-1. How far away are these newly-discovered worlds? They re about 40 light years from Earth. That means using today s rocket technology (and a whole lot of cash), it would probably take about 11,250 years to get to TRAPPIST-1. This Week: We found 7 Earth-sized planets orbiting a dwarf star, 3 of them in the habitable zone! Also, @NASA_SLS rocket test & more! Watch: pic.twitter.com/cbberkelu1 NASA (@NASA) February 25, 2017 I called up one of NASA s exoplanet experts, Aki Roberge, to help us break down the find. A specialist in planet formation, Roberge helps plan future missions for NASA, and confirms that the space agency nerds are just about as excited as we get about TRAPPIST-1. Here are 5 reasons why: Q: Why Are Scientists Freaking Out About TRAPPIST-1? Roberge: To be completely blunt, the most exciting thing for actual scientists is that these planets are close enough that we re actually going to be able to study them particularly when the James Webb Space Telescope launches (October 2018.) When that launches, it will have a real shot at actually taking a look at the atmospheres of these planets or if they have atmospheres at all. So it s like a promise of future excitement, in some ways. I can see why people would think this is more of the same stuff [NASA's] already been doing. And in some aspects, it is. But it s a smaller star, it s closer to us, and it s got more planets really tightly packed. The closer the system is to our solar system the more the star is like the Sun and the planet is like the Earth, the more likely we are to understand what we re looking at. That s what makes it exciting.
Q: Why is everyone calling these planets Earth-like? Roberge: At the moment, all you really tell from the transits is these are small black dots. We just get a radius and if we re super lucky as they were in the case of this system, they can get masses. The sizes and masses of these planets is really valuable information though, because it does suggest that most of them are rocky. Six of the seven planets look like they re rocky. And being Earth-sized, we think it s a good place: an atmosphere thick enough to keep you warm and last for billions of years, but not so thick that you end up being a gas giant planet. There are, however, several reasons to think that being a rock in the habitable zone of a red dwarf star is not actually a nice place to live, and that those environments are very different from our solar system. A lot of these investigations that are going forward over the next decade are to find the answers to these questions. The TRAPPIST-1 star has seven Earth-size planets orbiting it. This artist s concept appeared on the cover of Nature on Feb. 23, 2017. (Credit: NASA/JPL- Caltech) Q: Is there water on the surface of these planets? Roberge: Most of them are the right distance from a star that maybe they could have liquid water on their surfaces. But that s a huge maybe. Just look at our solar system: we have three rocky planets about the size of the TRAPPIST-1 planets. We ve got Earth, Venus and Mars in or near what astronomers call the habitable zone and they couldn t be more different! Q: What s the big deal about rocky planets? Roberge: As far as we know, that s the only kind of planet that we could have habitable conditions of life on life that we could actually understand or recognize from interstellar distances. The Earth is unique in the solar system in one really important way: it s the only planet that has surface life so abundant that it s affecting the atmosphere. That is noticeable from interstellar distances. So it s not really that we think Earth-like life is the only life that can be out there. It s just the only life we can detect. Q: What can non-scientists get excited about here?
Roberge: I think this would really bring it home to people that we have neighbors. I think a lot of people are used to thinking oh, exoplanets, those are all really distant. As far as the laws of physics go, you could get to TRAPPIST-1 in a human lifetime (~40 years traveling at the speed of light). So it becomes more of an engineering problem than a laws of physics problem. Exoplanet discovery: What does Nasa's announcement mean - and should we be excited about TRAPPIST-1? Chiara Palazzo / The Telegraph / 24 February 2017 Turns out it wasn t just dust on the telescope lens, Nasa astronomers have spotted seven Earth-size planets around a nearby star, some or all of which could harbour water and possibly life. Google has marked the Earth-shattering discovery with a Doodle, featuring the seven planets squeezing into view on the earth's telescope. What is TRAPPIST-1? TRAPPIST-1 stands for Transiting Planets and Planetesimals Small Telescope. The discovery is a small, dim star in the constellation Aquarius, less than 40 light-years from Earth, or 235 trillion miles away, according to Nasa and the Belgian-led research team who announced its discovery on Wednesday. An artist's conception of what the surface of the exoplanet TRAPPIST-1f may look like Seven planets circle Trappist-1, with orbits ranging from one and a half to 20 days. If Trappist-1 were our sun, all these planets would fit inside the orbit of Mercury. That's how close they are to their star and why their orbits are so short. The planets have no real names. They're only known by letters, "b" through "h." The letter "A" refers to the star itself. Can this newly discovered solar system support life? Six of TRAPPIST-1's "exoplanets" lie in a temperate zone where surface temperatures range from zero to 100C. Of these, at least three are thought to be capable of having watery oceans,
greatly increasing the likelihood of life. No other star system known contains such a large number of Earth-sized and probably rocky planets. All are about the same size as Earth or Venus, or slightly smaller. Because the parent star is so dim, the planets are warmed gently despite having orbits much smaller than that of Mercury, the planet closest to the sun. Scientists said they need to study the atmospheres before determining whether these rocky, terrestrial planets could support some sort of life. What do the planets and solar system look like? As well as being in tight orbits, the TRAPPIST-1 planets are unusually close to one another, conjuring an image straight out of science fiction. If Trappist-1 were our sun, all seven planets would be inside Mercury's orbit. Mercury is the innermost planet of our own solar system. How did they find out about TRAPPIST-1? The discovery, reported in the journal Nature, was made by astronomers using Nasa's exoplanet-hunting Spitzer Space Telescope. The telescope operates at the infrared wavelengths which glow brightest from TRAPPIST-1, and can detect the tiny dimming that occurs when a passing or "transiting" planet blocks out light from its star. Spitzer's data allowed the team to measure precisely the sizes of the seven planets and estimate the masses and densities of six of them. The Spitzer was launched in 2003, and was never meant to continue in space for this long but the telescope is still making discoveries beyond what was imagined. It follows the earth's orbit around the sun, but travels slightly slower, so over time it gets further away from the earth. It is now in its "final" phase, which lasts until 2018. What is an exoplanet anyway? An exoplanet is any planet that is outside of our solar system - ie anything that is not orbiting our star. The first exoplanet was discovered in 1988, but over 3,500 have been discovered since then. Only a tiny fraction of these have been deemed capable of supporting life in any way. Oceans and closeness to a star are two factors that scientists take into account. What next? Scientists need to study the atmospheres of these almost assuredly rocky planets before drawing any conclusions about water and life. The Hubble Space Telescope already is on the case and the still-under-construction James Webb Space Telescope will join in once it's launched next year. The Webb will search for gases that might be a byproduct of life: oxygen, ozone and methane. Scientists say it should take five years to get a handle on all these atmospheres, and figure out whether water - and maybe life - are present. http://webbtelescope.org/video/859/science
Pictures of space and planets : http://www.independent.co.uk/news/science/exoplanet-discovery-nasa-pictures-posters-lifetrappist-1-solar-system-announcement-a7594826.html