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Polarizing Coronagraph for Circumstellar Dust Observations by Göran Olofsson, Astronomy, SU Thursday the 16th of November 10.00 o'clock at FA32 Abstract The idea that there exists planetary systems other than that of the Sun is old, but it has until recently been beyond the technical feasibility to get any observational evidence for external planetary systems. By the IRAS discovery of far-IR dust emission around nearby stars, like Vega, it was realized that the dust replenishment required larger colliding or evaporating bodies, i.e. processes similar to those that provide the zodiacal dust. In addition, a steadily increasing number of planets are being found by detecting the minimal cyclic radial velocity variations of the central star caused by an orbiting planet. Obviously this (indirect) detection method works bests for heavy planets, orbiting close to their central stars, and there is an ongoing discussion what technical means it may take to do direct detection of planetary systems similar to our own. It has been argued that a new generation of extremely large ground-based telescopes (ELTs) may provide the tool for such observations (actually this is one of the main scientific drivers for the large investments required to build ELTs). But probably we have to wait for space interferometers, like Darwin, for the first detection of an Earth like planet orbiting an nearby star. Until then, much closer in time, we can explore the properties of circumstellar dust disks, and I will describe our own plans in that direction, both using Herschel Space Observatory and a 'home-made' polarizing coronagraph. Vega (IRAS) Disk evolution Silhouette disks Disk evolution betaPic_0.5µm betaPic_10µm A smooth decline of dust with time? ISO view The Spitzer sample Age 3-10 Myr N*/Ntot 50/ ~140 10-30 Myr 50/ ~110 30-100 50/ Myr ~130 100-300 50/ Myr ~100 0.3-1 Gyr 50/ ~1000 1-3 Gyr 50/ ~1000 Distance (pc) 80-160 Target 20-60 Tau, Oph, Cha, Lup, Upper Sco Tau, Oph, Cha, Lup, Cen Crux IC 2602 & Alpha Per Ursa Major, Castor, Pleiades Field stars, Hyades 20-60 Field stars 60-160 40-180 20-120 FEPS, only 15 stars with excess at 24 µm Cold dust - little or plenty? ? ? Disk evolution Kuiper belt The Sun+Kuiper belt at distance Wavelength m 70 100 130 Flux (10pc) Jy 0.004 0.007 0.008 Flux (20pc) Jy 0.001 0.002 0.002 Contrast ratio Ldust/Lsun Wavelength m 70 100 130 R (10pc) 0.04 0.14 0.27 R (20pc) 0.04 0.17 0.27 Planets, radial velocity QuickTime och en TIFF (LZW)-dekomprimerare krävs för att kunna se bilden. Orbits QuickTime och en TIFF (LZW)-dekomprimerare krävs för att kunna se bilden. Mass distribution QuickTime och en TIFF (LZW)-dekomprimerare krävs för att kunna se bilden. PSF Lyot Coronagraph Focal plane Relay lens Pupil stop EMCCD Seeing 0.7”, disk 1” diam Pupil image Seeing 0.7” disk =1” Seeing 0.7”, disk 3” diam Pupil image Seeing 0.7” disk 3” PSF, coronagraph Observed PSF Lyot Coronagraph Focal plane Relay lens Pupil stop EMCCD polarizer NGC 7023 Image sharpening Frame selection + MEM Shift-and-add, 20% PSF star MEM, 33 iterations Zoom PSF star betaPic Gas component TW Hya, 10 Myr B Pic, 10-20 Myr