1. Polarizing Coronagraph for Circumstellar Dust Observations
by Göran Olofsson, Astronomy, SU
Thursday the 16th of November 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.

2. Vega (IRAS)

3. Disk evolution

4. Silhouette disks

5. silh2

6. silh3

7. Silh4

8. Disk evolution

9. betaPic_0.5µm

10. betaPic_10µm

11. A smooth decline of dust with time?

12. ISO view

13. Age N*/Ntot Distance (pc) Target
Spitzer sample
The Spitzer sample
Age N*/Ntot Distance (pc) Target

14. FEPS, only 15 stars with excess at 24 µm
Spitzer_FEPS
FEPS, only 15 stars with excess at 24 µm

15. Herschel will see cold dust
Cold dust - little or plenty? ? ?

16. Disk evolution

17. The Sun+Kuiper belt at distance
Contrast ratio Ldust/Lsun

18. Planets, radial velocity

19. Orbits

20. Mass distribution

21. PSF

22. Lyot Coronagraph
Focal plane
Relay lens
Pupil stop
EMCCD

23. Seeing 0.7”, disk 1” diam
Pupil image

24. Seeing 0.7” disk =1”

25. Seeing 0.7”, disk 3” diam
Pupil image

26. Seeing 0.7” disk 3”

27. PSF, coronagraph

28. Observed PSF

29. Lyot Coronagraph
Focal plane
Relay lens
Pupil stop
polarizer
EMCCD

30. NGC 7023

31. Image sharpening

32. Frame selection + MEM
Shift-and-add, 20%
MEM, 33 iterations
PSF star

33. Zoom
PSF star

34. betaPic

35. Gas component
Gas component
TW Hya, 10 Myr
B Pic, Myr