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Histoire De La Cosmologie Histoire de la cosmologie Un cours offert aux étudiants de la Faculté des lettres, de la Faculté de biologie et de médecine, de la Faculté de géosciences et environnement, de la Faculté des sciences sociales et politiques et de la Faculté de théologie et de sciences des religions de l’Université de Lausanne dans le cadre de « Sciences au carré » Histoire de la cosmologie Histoire de la cosmologie 10 – Etoiles et galaxies 10.1 Etoiles et amas d’étoiles 10.2 Naissance des étoiles 10.3 Diagrammes H-R et C-M 10.4 Mort des étoiles Prof. Georges Meylan 10.5 Nébuleuse ou galaxie Laboratoire d’astrophysique 10.6 La Voie lactée, notre Galaxie Ecole Polytechnique Fédérale de Lausanne 10.7 Classification morphologique des galaxies 10.8 Groupes et amas de galaxies Site web du laboratoire et du cours : http://lastro.epfl.ch Voir le fichier 10-EtoilesetGalaxies.pdf sur le site web du laboratoire et du cours : http://lastro.epfl.ch Histoire de la cosmologie 10.1 10 – Etoiles et galaxies Bibliographie succincte Etoiles et amas d’étoiles • CELNIKIER, Ludwik M. Find a Hotter Place ! A History of Nuclear Astrophysics. London : World Scientific, 2006. • CHABERLOT, Frédéric. La Voie Lactée : Histoire des conceptions et des modèles de notre Galaxie des temps anciens aux années 1930. Paris : CNRS Editions, 2003. • COLLIN-ZAHN, Suzy. Des quasars aux trous noirs. Paris : EDP, 2009. • LEQUEUX, James. Naissance, évolution et mort des étoiles. Paris: EDP, 2011 • LUMINET, Jean-Pierre. Le destin de l’Univers. Paris : Fayard, 2006. APOD APOD 2010 April 18 2010 April 18 Grande Grande éruption éruption solaire solaire Satellite Stereo Satellite Stereo NASA NASA Notre Soleil est une étoile isolée rayon = 700’000 km rayon = 700’000 km à 150’000’000 km de la Terre à 150’000’000 km de la Terre Un amas ouvert tel que les Pléiades contient quelques centaines d’étoiles Amas ouvert h et χ Per L’amas globulaire 47 Tucanae Un amas globulaire contient quelques millions d’étoiles Un amas globulaire tel que ω Centauri contient quelques millions d’étoiles WFI camera at the 2.2-m MPG-ESO telescope at La Silla Observatory Un amas globulaire tel que ω Centauri Un amas globulaire tel que ω Centauri contient quelques millions d’étoiles contient quelques millions d’étoiles WFI camera at the 2.2-m MPG-ESO telescope at La Silla Observatory WFI camera at the 2.2-m MPG-ESO telescope at La Silla Observatory l’amas globulaire géant Omega Centauri VST ESO Paranal Chili Un amas globulaire tel que ω Centauri contient quelques millions d’étoiles June 2011 l’amas globulaire géant Omega Centauri VST ESO Paranal Chili l’amas globulaire géant Omega Centauri VST ESO Paranal Chili June 2011 June 2011 Visible/infrared comparison views of the newly discovered globular cluster VVV CL001 Problème à N corps Let a number, N, of particles interact classically through Newton's Laws of Motion and Newton's inverse square Law of Gravitation. The resulting equations of motion provide an approximate mathematical model with numerous applications in astrophysics, including the motion of the moon and other bodies in the Solar System (planets, asteroids, comets and meteor particles); stars in stellar systems ranging from binary and other multiple stars to star clusters and galaxies; and the motion of dark matter particles in cosmology. For N=1 and N=2 the equations can be solved analytically. The case N=3 provides one of the richest of all unsolved dynamical problems -- the general three-body problem. For problems dominated by one massive body, as in many planetary problems, approximate methods based on perturbation expansions have been developed. In stellar dynamics, astrophysicists have developed numerous numerical and theoretical approaches to the problem for larger values of N, including treatments based on the Boltzmann equation and the Fokker-Planck equation; such N-body systems can also be modelled as self-gravitating gases, and thermodynamic insights underpin much of our qualitative understanding. Douglas Heggie http://fr.arxiv.org/abs/astro-ph/0503600v2 ESO VISTA October 2011 Les trois lois de la mécanique newtonienne Problème à deux corps • Lex prima : de Newton Tout corps persévère dans l’état de repos ou de mouvement rectiligne uniforme à moins que quelque force n’agisse sur lui et ne le contraigne à changer d’état » • Lex secunda : de Newton Les changements qui arrivent dans le mvt sont proportionnels à la force motrice et se font dans la ligne droite dans laquelle cette force a été imprimée » • Lex tertia : de Newton L’action est toujours égale et opposée à la réaction, i.e., que les actions de deux corps l’un sur l’autre sont toujours égales et de direction opposées » Problème à deux corps Problème à deux corps Problème à deux corps Problème à deux corps 10.2 Naissance des étoiles Zoom into IC 2948 showing(a(group(( of(thick(clouds( IC 2948 / IC 2944 (of(dust(known(as( Running Chicken the(Thackeray( Nebula globules( Gum 39 & Gum 41 effondrement gravitationnel de nuages de gaz et de poussière la turbulence crée une hiérarchie de condensations comme la turbulence diminue localement, la contraction s’amorce dans chacune des condensations tandis que des régions se contractent, comme la turbulence diminue localement, des condensations individuelles s’effondrent et forme des étoiles la contraction s’amorce dans chacune des condensations tandis que des régions se contractent, tandis que des régions se contractent, des condensations individuelles s’effondrent et forme des étoiles des condensations individuelles s’effondrent et forme des étoiles tandis que des régions se contractent, dans les amas d’étoiles denses, des condensations peuvent fusionner des condensations individuelles s’effondrent et forme des étoiles lors de leur effondrement et donc contenir plusieurs proto-étoiles dans les amas d’étoiles denses, des condensations peuvent fusionner dans les amas d’étoiles denses, des condensations peuvent fusionner lors de leur effondrement et donc contenir plusieurs proto-étoiles lors de leur effondrement et donc contenir plusieurs proto-étoiles dans les amas d’étoiles denses, des condensations peuvent fusionner dans les amas d’étoiles denses, des condensations peuvent fusionner lors de leur effondrement et donc contenir plusieurs proto-étoiles lors de leur effondrement et donc contenir plusieurs proto-étoiles les rencontres gravitationnelles dans les amas d’étoiles denses, peuvent induire l’éjection d’étoiles les effets dynamique à N-corps influencent la croissance des masses les vents stellaires mettent fin à la formation d’étoiles il résulte un amas d’étoiles, parfois entouré d’une région HII 30 Doradus HST NASA/ESA Equilibre hydrostatique Equilibre hydrostatique Durant la séquence principale, l'étoile est en équilibre hydrostatique, elle subit deux forces qui s'opposent et la maintiennent en équilibre : d'une part les réactions thermonucléaires qui ont lieu au cœur de l'étoile exercent une pression (gazeuse et radiative) qui tend à la faire augmenter de volume, ce qui entraîne une diminution de la température de l'étoile ; d'autre part les forces de gravité reprennent le dessus lorsque la pression (gazeuse et radiative) diminue, elles ont tendance à la faire se contracter et donc à augmenter la température de l'étoile, de sorte que les réactions nucléaires s'intensifient et que la pression (gazeuse et radiative) augmente à nouveau. en tout point, le gradient de pression équilibre la gravitation en tout point, le gradient de pression équilibre la gravitation La constellation d’Orion La constellation d’Orion contient une pouponnière d’étoiles La nébuleuse d’Orion vue par le Hubble Space Telescope Gas in the Eagle Nebula (M16) : Pillars of Creation in a Star-Forming Region NASA/ESA 1995 visible IR Gas in the Eagle Nebula (M16) : Pillars of Creation in a Star-Forming Region NASA/ESA 2015 Gas in the Eagle Nebula (M16) : Pillars of Creation in a Star-Forming Region NASA/ESA 2015 VISIBLE IR 2015 WFC3 1995 WFPC2 Gas in the Eagle Nebula (M16) : Pillars of Creation in a Star-Forming Region NASA/ESA 2015 Gas in the Eagle Nebula (M16) : Pillars of Creation in a Star-Forming Region NASA/ESA Gas in the Eagle Nebula (M16) : Pillars of Creation in a Star-Forming Region NASA/ESA 1995 Gas in the Eagle Nebula (M16) : Pillars of Creation in a Star-Forming Region NASA/ESA 2015 HST NASA/ESA Carina HST NASA/ESA formation d’une étoile et d’un disque, lieu de futures planètes Illustration of disk evolution in relation to planet formation Herbig-Haro 110 is a geyser of hot gas from a newborn star that splashes up against and ricochets off the dense core of a cloud of molecular H. NASA/ESA 3 July 2012 Planet formation: this image illustrates a protoplanetary disk undergoing spiral wave instabilities as it would appear using a millimeter wave telescope. Today, it is generally thought that planets formed by the hierarchical accretion of larger and larger sized bodies, from dust to planets. Artist vision Indiana University 2004 the sharpest image ever taken by ALMA showing the protoplanetary disc HL Tauri : surrounding the young star HL Tauri. This is a composite image of the young star HL Tauri and its surroundings using data from ALMA (enlarged in box at upper right) and the NASA/ESA Hubble Space Telescope (rest of the picture). This is the first ALMA image where the image sharpness These new ALMA observations reveal substructures within the disc that have never been seen exceeds that normally attained with Hubble. before and even show the possible positions of planets forming in the dark patches within the Credit: ALMA (ESO/NAOJ/NRAO), Hubble (NASA/ESA) Nov. 2014 system. Credit: ALMA (ESO/NAOJ/NRAO) Les étoiles nous apparaissent globalement sous deux formes différentes • Les étoiles « proches » sont dites « résolues » lorsqu’elles sont observées 10.3 comme des points lumineux séparés les uns des autres.
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