"Skybuck Flying" <nospam@hotmail.com> wrote in message news:<cjkrr7$gqf$1@news3.zwoll1.ov.home.nl>...

My idea is to use the SUN as a way to send a message to aliens ;)
We build a big shield around the sun. And then we can turn it on and off
like a lamp.

[...]

Has anybody ever though about analyzing stars ???? 
Maybe other aliens have already though up the same idea ;)
Maybe aliens are already trying to send a message to us by using the stars

Not exactly the same but related: Andy Fabian of Cambridge University
wrote a paper in 1977 which, in part, talks about: "Modulating the
X-ray luminosity of an X-ray source may also be possible with the aid
of an orbiting metal screen about one million km in size."

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http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1977JBIS...30..112F&db_key=AST&high=415592bab827045

Title: Signalling over stellar distances with X-rays
Authors: Fabian, A. C.
Journal: British Interplanetary Society, Journal (Interstellar
Studies), vol. 30, Mar. 1977, p. 112, 113.

Abstract
It is shown in a rough calculation that a chunk of rock about 1 km in
size and of mass 10 to the 13th power kg dropped onto a neutron star
could produce an X-ray pulse of about 10 to the 36th power ergs,
strong enough to be detectable throughout the Galaxy. An advanced
civilization with mobility over a region a few parsecs in size may
therefore be able to transmit a crude broadband and omnidirectional
X-ray signal. Modulating the X-ray luminosity of an X-ray source may
also be possible with the aid of an orbiting metal screen about one
million km in size.
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   Henry