Detecting Dark Energy Michael Levi Lawrence Berkeley National Laboratory Detecting Dark Energy or, Is Larry a Cosmological Constant? The Mystery: Where does he get his energy from? Why is he still so youthful? The Postulate: Underlying energetic scalar field with strong “LS” couplings. Scalar field is dynamical so we feel it differently from Larry. The Cosmological Constant The Cosmological Constant is back!!! L L • Einstein 1917 – Field equations show contracting or expanding universe, but the universe was thought to be static. – Einstein postulated a cosmological constant, L “energy” (with negative pressure), to maintain a static universe. Einstein’s field equations (1917) The Cosmological Constant is back!!! L L • Danger! Runaway solution if L is large and positive! Edwin Hubble • To measure the expansion rate of the universe Hubble needed to measure astronomical distances • Apparent brightness of an object depends on its distance • If a set of identical objects could be found (“standard candles”) then brightness could be used to determine their distances The Universe, its Expanding! Hubble’s 1929 evidence that the universe is not static. The Cosmological Constant is unnecessary -- Einstein’s proclaimed his “Biggest Blunder.” The Fate of the Universe Average distance between galaxies Slowing Forever Time The Fate of the Universe Average distance between galaxies Slowing Forever Big Crunch Time “Standard” Candles •Nearby supernovae used to study SNe light curve (z<0.1) •Brightness not quite standard •Intrinsically brighter SNe last longer •Correction factor needed Peakmagnitude dispersion of 0.25 – 0.3 magnitudes ~0.15 magnitude dispersion “Brookline is expanding!” The Accelerating Universe What is causing this accelerating expansion? – Some kind of ‘dark energy’ that counteracts gravity? L L A Revolution in Cosmology Big Bang Nucleosynthesis Inflation Flat universe total= 1.02+/-0.02 Baryon Density B= 0.044+/-0.004 DE= 0.7, M= 0.3 for a flat universe Weak lensing mass census Large scale structure measurements M= 0.3 WMAP New Standard Cosmology: 73±4% Dark Energy 27±4% Matter 0.5% Bright Stars Matter: 22% CDM, 4.4% Baryons, 0.3% ’s Energy budget of Universe Dark Energy: 65% Dark Matter: 30% Fundamental Physics Questions • What is the Nature of the dark energy? —The dominant component of our universe. —Dark energy does not fit in current physics theory. —Theory proposes a number of alternative new physics explanations, each with different properties we can measure. • Two key contrasting theories of dark energy. — vacuum energy, constant over time: Deep philosophical implications, why are the matter (M) and energy densities (L) nearly the same today, they have totally different time evolution. Why now? Why is L so small? — or, time dependent possibly a dynamical scalar field: Might explain M @ L and so small, we’ve seen these fields elsewhere in particle physics and in the theory of inflation. Points to new physics. The Expansion History of the Universe Need lots of precision data to study this region Need Lots more Data! Turn Dozens of Supernovae Thousands Supernovae Space Ground Z=0.8 Z=1.0 Z=1.2 Z=1.4 Z=1.6 Supernova / Acceleration Probe SNAP is “Dog Simple”: Innovation in Simplicity • Innovative 2m aperture telescope design does IR imaging with room temperature optics • Built in end-to-end optical test capability simplifies Integration and testing • The fixed antenna, fixed solar panels eliminates a major mission risk. • Fixed filters, passive cooling, eliminates instrument risk. • No onboard data analysis: all images are downlinked to Earth D=56.6 cm (13.0 mrad) 0.7 square degrees! Focal plane Fixed filters atop the sensors Guider NIR Visible Integral Field Spectrograph Spectrograph port SNAP Surveys Survey Deep/SNe Wide Area(sq.deg) Depth(AB mag) ngal(arcmin-2) Ngal 15 30.3 250 107 1000 28.0 100 108.5 26.7 40-50 Panoramic 7000-10000 Hubble Deep Field 109 Base SNAP survey: 15 square degrees near ecliptic poles ~9,000 as large as Hubble Deep Field, same resolution but deeper (and in nine visible and NIR bands) GOODS Survey area SNAP Collaboration LBNL G. Aldering, S. Bailey, C. Bebek, W. Carithers, L. Cominsky†, T. Davis†, K. Dawson, S. Deustua†, D. Groom, M. Hoff, S. Holland, D. Huterer†, A. Karcher, A. Kim, W. Kolbe, B. Krieger, G. Kushner, N. Kuznetsova, R. Lafever, M. Levi, S. Loken, B. McGinnis, R. Miquel, P. Nugent, H. Oluseyi†, P. Platt†, N. Palaio, S. Perlmutter, N. Roe, H. Shukla, A. Spadafora, H. Von Der Lippe, J-P. Walder, G. Wang Berkeley M. Bester, E. Commins, G. Goldhaber, H. Heetderks, P. Jelinsky, M. Lampton, E. Linder, D. Pankow, M. Sholl, G. Smoot, C. Vale, M. White Caltech R. Ellis, R. Massey†, A. Refregier†, R. Smith, K. Taylor, A. Weinstein Fermi National Laboratory J. Annis, F. DeJongh, S. Dodelson, T. Diehl, J. Frieman, D. Holz†, L. Hui, S. Kent, P. Limon, J. Marriner, H. Lin, J. Peoples, V. Scarpine, A. Stebbins, C. Stoughton, D. Tucker, W. Wester Indiana U. C. Bower, N. Mostek, J. Musser, S. Mufson IN2P3-Paris -Marseille P. Astier, E. Barrelet, R. Pain, G. Smadja†, D. Vincent A. Bonissent, A. Ealet, D. Fouchez, A. Tilquin JPL D. Cole, M. Frerking, J. Rhodes, M. Seiffert LAM (France) S. Basa, R. Malina, A. Mazure, E. Prieto University of Michigan B. Bigelow, M. Brown, M. Campbell, D. Gerdes, W. Lorenzon, T. McKay, S. McKee, M. Schubnell, G. Tarle, A. Tomasch University of Pennsylvania G. Bernstein, L. Gladney, B. Jain, D. Rusin University of Stockholm R. Amanullah, L. Bergström, A. Goobar, E. Mörtsell SLAC W. Althouse, R. Blandford, W. Craig, S. Kahn, M. Huffer, P. Marshall STScI R. Bohlin, D. Figer, A. Fruchter, B. Mobasher Yale U. C. Baltay, W. Emmet, J. Snyder, A. Szymkowiak, D. Rabinowitz, N. Morgan † Institutional affiliation Optical Sensors Infra-Red Sensors Electronics Space Optics Spectrograph Earth Orbit L2 Telescope National Academy of Sciences Department of Energy NASA OSTP JDEM Expansion History of the Universe We live in a special time when: - we can ask questions about the history and fate of the universe - and expect to get an answer! “Brookline is expanding!”