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Dark Matter & Dark Energy Dark Matter & Dark Energy Orin Harris and Greg Anderson Department of Physics & Astronomy Northeastern Illinois University Spring 2021 c 2012-2021 G. Anderson., O. Harris Universe: Past, Present & Future – slide 1 / 88 Outline Overview Dark Matter Structure Our Accelerating Universe Review c 2012-2021 G. Anderson., O. Harris Universe: Past, Present & Future – slide 2 / 88 Overview A Great Unknown Pie Chart Visible Matter in the Universe Dark Matter & Dark Energy Dark Matter Structure Our Accelerating Overview Universe Review c 2012-2021 G. Anderson., O. Harris Universe: Past, Present & Future – slide 3 / 88 A Great Unknown Q What is the universe made of? A Mostly, we do not know! The vast majority of the universe can not be “seen”, it is composed of dark matter and dark energy. c 2012-2021 G. Anderson., O. Harris Universe: Past, Present & Future – slide 4 / 88 What is the Universe made of? Dark Matter 24% Ordinary Matter 4.6%: ∼ Outside Stars: 3.8% Stars: 0.6% Dark Energy 71.4% ∼ The mass of dark matter in galaxies, clusters of galaxies, and the universe is five to six times the mass of ordinary matter. c 2012-2021 G. Anderson., O. Harris Universe: Past, Present & Future – slide 5 / 88 Visible Matter in the Universe Visible matter: stars, gas, dust There is more mass in gas than in stars. On large scales, > 100 1000 Mpc, matter appears∼ − to be isotropic and homogeneous. c 2012-2021 G. Anderson., O. Harris Universe: Past, Present & Future – slide 6 / 88 Dark Matter & Dark Energy We know very little about 95% of the universe which is dark invisible. Dark matter is the invisible mass which surrounds galaxies and galactic clusters. The presence of dark matter is inferred by its gravitational effects on observable stars, gas, galaxies, .... Dark energy is the energy which is causing the expansion of the universe to accelerate. dark energy = cosmological constant = vacuum energy c 2012-2021 G. Anderson., O. Harris Universe: Past, Present & Future – slide 7 / 88 Overview Dark Matter Q: “Dark” Matter? Dark matter history Particle Discovery Timeline Evidence for Dark Matter Andromeda Dark Matter Merry-Go-Round Planet Speeds Rotation Curves Expectations vs. Dark Matter Doppler Effect 16.07 Rubin The Andromeda Galaxy (M31) Milky Way Dark Matter Halo Q: Rotation Curves? Q: Rotation without DM? Q: Dark Matter Distribution? m60 Spectral Line c 2012-2021 G. Anderson., O. Harris Universe: Past, Present & Future – slide 8 / 88 Broadening Q: “Dark” Matter? Why do we call dark matter ”dark”? A) It absorbs light B) It is dark in color C) It emits little or no radiation of any wavelength D) It blocks out the light of stars in a galaxy c 2012-2021 G. Anderson., O. Harris Universe: Past, Present & Future – slide 9 / 88 Dark matter history 1930s Speeds of galaxies in galaxy clusters, stars in spiral galaxies, indicate M M . Assumed to be dead stars, gas, dust. dark ≫ luminous 1956 Neutrinos detected. A type of dark matter! By 1980’s mass understood to be too small to account for dark matter. 1970s Increasing accuracy of evidence in spiral galaxies. Telescopes rule out gas/dust as explanation. Sense of crisis!. → 1980s Gravitational lensing gives further evidence of dark matter. Modified Gravity proposed, but conflicts with relativity. “Dark” particles are leading explanation; laboratory searches begin. 1990s Ordinary matter ruled out (absorption/microlensing/BBN). CMB is precise: M =5.5 M dark × luminous Today Experiments have not yet detected dark matter in the lab. It is possible it is too weakly interacting to be detected directly. c 2012-2021G.Anderson.,O.Harris Universe:Past,Present&Future – slide 10 / 88 Particle Discovery Timeline b t b H W,Zb −b b b Ω Υ ∆ b b τb b0 ±b Σ0 Ξ nb Λ Σ b b p b p b K ρb b± b η b π π0 J/ψ µb −b b e e+ b b ντ b νµ νe γb gb 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 c 2012-2021G.Anderson.,O.Harris Universe:Past,Present&Future – slide 11 / 88 Evidence for Dark Matter From individual galaxies • – Rotation curves of spiral galaxies – Broadening of spectral lines in elliptical galaxies Clusters of galaxies • – Velocities of galaxies – Temperature of hot Gas – Gravitational lensing Primordial Nucleosynthesis • Temperature fluctuations in the CMB • Structure Formation • c 2012-2021G.Anderson.,O.Harris Universe:Past,Present&Future – slide 12 / 88 M31: The Andromeda Galaxy Merry-Go-Round Rotation Curve A plot of orbital speed versus orbital distance from the center of rotation. v Cbc bc bc bc B A B C bc speed Abc distance r v = ωr c 2012-2021G.Anderson.,O.Harris Universe:Past,Present&Future – slide 14 / 88 Orbital Speeds of Planets 12 vp = vtperiod = distance = 2πr 10 bc Mercury v = 2πr = 2π ⇒ p √r 8 bc Venus (because Kepler: p2 = r3) bc 6 bc Mars GM (AU/years) Newton: v = q r ⊙ v 4 Jupiterbc Saturn bc Uranus 2 bc Neptunebc 0 0 10r (AU) 20 30 c 2012-2021G.Anderson.,O.Harris Universe:Past,Present&Future – slide 15 / 88 Rotation Curves M(r) = mass inside radius r. b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b GM r b ( ) b b b b b b b b b b b b b v(r)= b b b b b b b b b b b b q r b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b bb b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b r b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b uniform densityb b b b b b b b b b b b b bb b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b bb b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b decreasing density b b b 2 b b b b b b b rv b b b b b M(r)= b b G b b c 2012-2021G.Anderson.,O.Harris Universe:Past,Present&Future – slide 16 / 88 Expectations vs.
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