Polarizing Coronagraph for Circumstellar Dust Observations

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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 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.
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Vega (IRAS)
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Disk evolution
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Silhouette disks
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silh2
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silh3
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Silh4
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Disk evolution
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betaPic_0.5µm
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betaPic_10µm
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A smooth decline of dust with time?
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ISO view
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Spitzer sample
The Spitzer sample
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Spitzer_FEPS
FEPS, only 15 stars with excess at 24 µm
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Herschel will see cold dust
Cold dust - little or plenty?
?
?
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Disk evolution
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Kuiper belt
The SunKuiper belt at distance
Contrast ratio Ldust/Lsun
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Planets, radial velocity
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Orbits
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Mass distribution
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PSF
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Lyot Coronagraph
Focal plane
Relay lens
Pupil stop
EMCCD
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Seeing 0.7, disk 1 diam
Pupil image
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Seeing 0.7 disk 1
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Seeing 0.7, disk 3 diam
Pupil image
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Seeing 0.7 disk 3
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PSF, coronagraph
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Observed PSF
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Lyot Coronagraph
Focal plane
Relay lens
Pupil stop
polarizer
EMCCD
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NGC 7023
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Image sharpening
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Frame selection MEM
Shift-and-add, 20
MEM, 33 iterations
PSF star
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Zoom
PSF star
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betaPic
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Gas component
Gas component
TW Hya, 10 Myr
B Pic, 10-20 Myr