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Debris finder, PolCor-2
An instrument to detect debris around young stars


  1. Introduction
  2. Exoplanets
  3. Stars dust disc
  4. Albanova, research center in Stockholm
  5. The instrument, PolCor-2
  6. The mechanical box's surfaces
  7. Coronagraph
  8. Mirror set one
  9. Filters
  10. Lyot Stop
  11. Servo motors
  12. Polarizer
  13. Parabolic and flat mirror set two
  14. Lucky Imaging
  15. The camera
  16. The computer
  17. Test of the instrument that has been done
  18. Conclusion
  19. End of demonstration
  20. Follow up with links of information about coronagraphs

3: Stars dust disc

The planets are (reasonably) built up by the dust that is in orbit around a young star, usually in the form of a disk. Studying this dust disk in various stages of development around different stars contribute knowledge that can be used to build better mathematical models of how this development takes place. And the need for the new planets we've discovered with the Doppler method does not fit at all into the older mathematical models. It is predominantly very large planets, like Jupiter and bigger, and in many cases in an orbit very close to their star. That there are giant planets discovered today is because today's insensitive technology, the major planet's are easier to detect. But even they must be able to fit into the mathematical models.

Our own solar system as seen from a long distance would look like a dust disk with a hole in the central part where the planets are, looks like a donut. That follows from studies from Earth of our own dust disc from "inside" and try to see the "hole", but this is almost impossible to see or at least very difficult. The dust is there, we can see, even without instruments, that is the Zodiacal light. Zodiacal light which can be seen in dark places after sunset, just the Sun's reflection in the dust.

The dust are in the same plane as the orbits of the planets, but much more can not be said about the form.

Seeing the dust disk and its shape around other stars can be done with the right technology. The hole has thus emerged as the planets formed from this material, as a vacuum cleaner in this area when they grown up. Around our sun should this hole may have a radius of about 40 a.u. (a.u. = astronomical units, 1 a.u. equal to the distance from the Earth to the Sun).

Our most distant planet is Pluto with a distance of about 40 a.u. from the Sun. Some say today that Pluto is not a planet, and it may not even not formed in the inner hole in the dust disc, the orbit it follow are heavily tilted and more elliptical relative to the other planets.

The contrast between the star's emitted light, and what is reflected in the dust is huge. One way to reduce this problem is to study the thermal radiation that dust emits instead, which still has great contrast, but is somewhat more manageable.

It is this dust disc you want to study around other stars in various stages of development. We dive now into the technology that makes it possible to make these observations.

Debris finder or planet hunter

Image from a test of PolCor-2 (the instrument I will talk about here), a giant star with clear dust counter, the picture is 1' across. The object is no young star but a star with slightly larger mass than our sun, and throwing out the dust at high speed. The object is selected from previous radio observations where the object of dust clouds appear as two peaks (the Doppler effect from the parts of disc that move toward and away from us).

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