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Astrophysics & Cosmology Erik Elfgren Luleå Civilingengör Exchange student Luleå tekniska universitet École polytechnique Msc Physics Summer job Summer student Cavendish laboratory CERN Université de Montréal • Dust CMB light Star light 1st stars Supernova Dust Dust emission Planck detector • Detection with Planck satellite? CMB Angular correlation Local dust Planck noise Early dust 180º/angle • Preons n He p u d β δ Proton Quark p u n Atom Nucleus β (βδ) (αδ) (αβ) (βδ) (αδ) (αβ) α β δ Z* α νe μ+ ντ u s c Z0/Z’ W+ β e- νμ τ- d X b W- Z’/Z0 W’- β δ νκ1 κ+ νκ2 h k t Z* W’+ Z” Leptons Quarks Force carriers α δ • Heavy neutrinos Gamma ray intensity N N Lecture 1 Overview Orion nebula What is science? To understand the universe, astrophysicists use the laws of physics to construct testable theories and models. Scientific method • Based on observation, logic, and skepticism. Hypothesis • A collection of well thought- out ideas to explain a phenomenon Model • Hypotheses that have withstood observational and experimental tests. Theory • A well- founded body of related hypotheses and models that form a self- consistent description of nature. Astrophysics The solar system Our Sun Terrestrial Planets Mercury, Venus, Earth, Mars Asteroid Belt Small rocky bodies Gas Giant Planets Jupiter, Saturn, Uransus, Neptune Kuiper belt Belt of icy objects Terminal shock Protects the solar system Oort cloud Ice rocks (50 000 AU) Astrophysics Stars A large, glowing ball of gas that generates heat and light through nuclear fusion Astrophysics Planets A moderately large object which orbits a star; it shines by reflected light. Planets may be rocky, icy, or gaseous in composition. Dwarf planets Pluto, Ceres, Eris Astrophysics Moons Objects which orbits a planet There are about 100 known moons in the solar system Astrophysics Asteroids Small and rocky objects that orbit a star A few hundreds of kilometres in diameter down to rocks just tens of metres. The Patroclus system, near Jupiter Astrophysics Meteroids Rocky objects (<10m) in the solar system A few hundreds of kilometres in diameter down to rocks just tens of metres. The Barringer Crater Astrophysics Comets Small and icy objects with a coma that orbit a star The coma is the nebulous envelope around the nucleus of a comet Halley’s comet Astrophysics Nebula An interstellar cloud of gas and/or dust Planetary nebulae The gaseous shells ejected from low-mass giant stars when they transform into white dwarfs Protoplanetary nebula Just before planetery nebula Supernova remnants Leftovers after supernovae Astrophysics Galaxies A great island of stars in space, all held together by gravity and orbiting a common center Most galaxies seem to have a giant black hole in their center The Milky way Astrophysics Distances • Light travels with a finite speed • It takes 8 minutes to reach us from the Sun 8 years to reach us from Sirius (8 light-years away) 1,500 years to reach us from the Orion Nebula • The farther out we look into the Universe, the farther back in time we see! • The universe is 13.7 × 109 years old 13.7 × 109 ly away (and counting!) we can see Astrophysics Distances • Distances are measured in light-years (ly) or parsecs (pc) 1 ly = 9.4605284 × 1015 m 1 pc = 3.08568025 × 1016 m ≈ 3.26 ly • Small distances are measured in astronomical units (AU) 1 AU = 3.08568025 × 1016 (1.496 × 108 km) • Cosmic distances are often measured in redshift, z Astrophysics Angles Astrophysics Angles Astrophysics Small angles 1º = 60 arcminutes = 60’ (bågminuter) 1’ = 60 arcseconds = 60” (bågsekunder) Example: On January 1, 2001, the planet Saturn had an angular diameter of 19.7” as viewed from Earth. Proxima Centauri has a parallax of 0.77” Astrophysics Small angle approximation D = 2 d tan(X·π/1,296,000) ≈ X·d/206,265 where X is the angular size (in arcseconds), D is the linear size of the object and d is the linear distance to the object. Astrophysics Solar constants • The Sun is denoted by the symbol • The mass of the Sun is M = 1.9891×1030 kg • The luminosity (=emitted electromagntic energy) is L = 3.846×1026 W • These are often used as units of measurement for celestial bodies, e.g. the mass of the black hole in the center of the Milky way has a mass of 3.7×106 M Astrophysics The Milky way 300 109 stars, 0.1 Mly, 5.8 1011 M Astrophysics The local group 3 galaxies, 37 dwarf galaxies, 10 Mly, 1012 M Astrophysics The Virgo supercluster 100 groups, 2000 galaxies, 200 Mly, 1015 M Cosmology The Millennium simulation Evolution of the universe with 1010 particles Cosmology The Expanding Universe The “fabric” of the space expands Cosmology The Big Bang • Happened some 13.7 ×109 years ago • The first atoms (H and He) formed in the first 3 minutes • The universe expanded and cooled quickly • The theory was “proven” by the Cosmic Microwave Background Cosmology The Cosmic Microwave Background • Was released some 400,000 years after the Big Bang • Is an almost perfect Black-body radiation with temperature 2.73 K • Is isotropic to a factor 10-5 • The tiny fluctuations tell us about the structure of the universe • Is the single most powerful tool in cosmology Cosmology Energy and Matter in the Universe • 1% is in stars and gas • 5% is ordinary matter • 25% is dark matter • 70% is dark energy