Polarizing Coronagraph for Circumstellar Dust Observations
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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 that there exists planetary systems other than that of the Sun is old, but it has until recently bee 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 an orbiting planet. Obviously this (indirect) detection method works bests for heavy planets, orbiti lose to their central stars, and there is an ongoing discussion what technical means it may take to d direct detection of planetary systems similar to our own. It has been argued that a new generation of tremely large ground-based telescopes (ELTs) may provide the tool for such observations (actually thi s 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. then, much closer in time, we can explore the properties of circumstellar dust disks, and I will des wn plans in that direction, both using Herschel Space Observatory and a 'home-made' polarizing corona
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Polarizing Coronagraph for Circumstellar Dust Observations. Polarizing Coronagraph for Circumstellar Dust Observations by Göran Olofsson, Astronomy, SU Thursday the 16th of November 10.00 o'clock at FA32 Abstract - PowerPoint PPT Presentation
Transcript of Polarizing Coronagraph for Circumstellar Dust Observations
Polarizing Coronagraph for Circumstellar Dust Observations
Polarizing Coronagraph for Circumstellar Dust Observationsby 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
silh2
silh3
Silh4
Disk evolution
betaPic_0.5µm
betaPic_10µm
A smooth decline of dust with time?
ISO view
Spitzer sample
The Spitzer sample
3-10 Myr 50/~140
80-160 Tau, Oph, Cha,Lup, Upper Sco
10-30 Myr 50/~110
60-160 Tau, Oph, Cha,Lup, Cen Crux
30-100Myr
50/~130
40-180 IC 2602 &Alpha Per
100-300Myr
50/~100
20-120 Ursa Major,Castor, Pleiades
0.3-1 Gyr 50/~1000
20-60 Field stars, Hyades
1-3 Gyr 50/~1000
20-60 Field stars
Age N*/Ntot Distance (pc) Target
Spitzer_FEPSFEPS, only 15 stars with excess at 24 µm
Herschel will see cold dustCold dust - little or plenty?
?
?
Disk evolution
Kuiper belt
Wavelength m Flux (10pc) Jy Flux (20pc) Jy70 0.004 0.001100 0.007 0.002130 0.008 0.002
Wavelength m R (10pc) R (20pc)70 0.04 0.04100 0.14 0.17130 0.27 0.27
Contrast ratio Ldust/Lsun
The Sun+Kuiper belt at distance
Planets, radial velocity
QuickTime och enTIFF (LZW)-dekomprimerare
krävs för att kunna se bilden.
Orbits
QuickTime och enTIFF (LZW)-dekomprimerare
krävs för att kunna se bilden.
Mass distribution
QuickTime och enTIFF (LZW)-dekomprimerare
krävs för att kunna se bilden.
PSF
Focal plane
Relay lens
Pupil stop
EMCCD
Lyot Coronagraph
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
Focal plane
Relay lens
Pupil stop
EMCCD
Lyot Coronagraph
polarizer
NGC 7023
Image sharpening
Frame selection + MEM
PSF star
Shift-and-add, 20% MEM, 33 iterations
ZoomPSF star
betaPic
Gas componentTW Hya, 10 Myr
Pic, 10-20 Myr
Gas component
