Universe-the-Solar-System.pdf

Universe-the-Solar-System.pdf

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  TP 1: TheEarth, the Universe, the Solar System Abilities and attitudes 1. Identify the expressions in the text by highlighting them: star, solar system, planet, galaxy. Then give a definition and example of each. 2. To express astronomical distances, we use a unit of length: the light year. It measures the distance L traveled by light at a speed c of 300,000 km/s for 1 year (t). Ccalculate the number of km corresponding to 1 light year 3. What question did scientists likely ask themselves when they discovered exoplanets like Gliese 581 c? 4. Propose an approach that would guide research. understand a text; extract useful information; communicate in appropriate scientific language regain knowledge (physics and mathematics) Practice a scientific approach NASA would have discovered another planet Earth teeming with life It's now official. The Earth is not the only habitable planet in the universe, its 'cousin' Kepler-452b has a sun identical to ours and is in orbit around its star at the same distance as the Earth from the his. In all civilizations, Man has always been intrigued both by his own origin and that of life: is life a universal phenomenon or is it unique on Earth? The idea that intelligent life can exist elsewhere than on Earth is not new: it goes back to the Ionian philosopher *, Anaximander of Miletus, who affirmed the plurality of inhabited worlds. (* school of philosophy which undertook a vast investigation into nature in the 6th and 7th centuries BC) We thought since the 1980s that we were alone around the Sun and that Earth was most likely the only place in the solar system that harbors life... But the sun is not the only star in the Milky Way... The closest star to the Sun is 4 light years away and the Milky Way is not the only galaxy in the Universe (the closest is more than 5 billion light years away.) Are the other stars in our galaxy surrounded by planets, do other inhabited lands exist? The scientific progress necessary to gather information on this subject is being accomplished before our eyes... Using the HARPES spectrograph on ESO's 3-6- m telescope, astronomers discovered in 2007 the most Earth-like planet outside our Solar System to date, an exoplanet with a radius of only 50 % larger than Earth. This exoplanet orbits the red dwarf Gliese 581, a star located 20.5 light years away in the constellation Libra. L = c .t
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  Everything seems togo in the direction that this new Earth is (or was, unfortunately,) crowded with life, the next step will be to detect artificial signals coming from this world. The fact is that this exoplanet's sun is 1.5 billion years older than ours and the planet's oceans can potentially evaporate into space. This same fate will be reserved for the Earth in several billion years. The fact is that it was the first habitable planet similar to Earth that was discovered. Eureka!”, Archimedes would have shouted, if he were part of the team of astronomers who have just taken a crucial step in the quest for a “habitable” twin Earth. These scientists, led by a NASA astronomer and whose work was published this Thursday in the American journal “Science”, discovered thanks to the American Kepler space telescope the first planet of a size comparable to Earth and on which the Water could exist in a liquid state, making life possible. If it is ruled out for humans to “live” there one day – this exoplanet is still located 4.6 million billion kilometers from our Sun – this discovery reinforces the probability of finding sister planets of the Earth in our galaxy, the Milky Way. “What makes this discovery particularly interesting is the fact that this planet called Kepler-186f is of Earth size in orbit around a so-called dwarf star, smaller and cooler than the sun, in the temperate zone where the water can be liquid,” says Elisa Quintana, an astronomer from the SETI Institute at NASA’s Ames Research Center, who led this research. “This is the first Earth-sized exoplanet found in the habitable zone of another star,” she insists. The “habitable” zone Kepler-186f is located in a star system 490 light years from the Sun (one light year is 9.46 trillion kilometers) with five planets orbiting a “sun”. But while its four “sisters” are too close to this sun, only Kepler-186f is in the so-called habitable zone, the one where life as we know it and which depends on the presence of water, has the greatest probability to develop there. It orbits its star in 130 days and receives a third of the light energy that Earth gets from the sun. Being in the habitable zone, however, is not enough to accommodate life. Of the nearly 1,800 exoplanets detected over the last 20 years, around twenty are orbiting their star in the habitable zone. But these planets are significantly larger than Earth and therefore it is difficult, given their size, to determine whether they are gaseous or rocky. The perfect size? The planet Kepler-186f has a radius 1.1 times that of Earth. According to theoretical models of planetary formation, planets with a radius less than 1.5 times that of Earth are unlikely to accumulate a thick atmosphere like the giant gas planets of our solar system. Kepler -186f thus enters the category of rocky planets in our solar system such as Earth, Mars or Venus. “Given the small size of this exoplanet, there is a high probability that it is rocky and has an atmosphere. If this atmosphere offers good conditions, water can exist in a liquid state on the surface,” explains Emeline Bolmont, a researcher at the University of Bordeaux who participated in this advance. She emphasizes that these
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  conclusions are basedon extrapolations because “to be sure that it is rocky we would need to have the mass of the planet which is not possible with current instruments”. An “important step” in the quest for a second land For Fred Adams, professor of physics and astronomy at the University of Michigan, “this is an important step in the quest to discover an exoplanet identical to Earth.” In other words, the objective of the Kepler mission. “Future NASA missions such as the James Webb space telescope (which will succeed Hubble in 2018 and will be more powerful, editor’s note), will be able to discover the closest rocky exoplanets and determine their composition as well as the nature of their atmosphere,” he said. said Paul Hertz, director of the space agency's astrophysics division, during a press conference. At the end of 2013, astronomers estimated that billions of Earth-sized planets orbiting stars similar to the Sun in our galaxy would be potentially habitable. The researchers based themselves on data from the first three years of observation by Kepler launched in 2009 to examine more than 100,000 stars resembling our Sun located in the constellations Cygnus and Lyra.