[daip] Question

[Leonia Kogan]

Dear Guillaume,

As you may know the classical(optical) astronomy has learned the universe by 
receiving signal at the very narrow banwidth of electro magnetic field.
This bandwidth is limited by lambda~0.5 micron (red) and ~0.7micron (blue).
The men's yes are sensitive to  this wavelength range of electro magnetic field.
But it is clear that the nature does not work specifically for the men.

So it can be expected that universe objects emit electromagnetic waves outside 
of the optic range. That is why recentely other astronomy appeared:
radioastronomy, X-ray astronomy, infrared astronomy..

All these astronomies study Universe in diferent wavelength of the electro 
magnetic field.

Now spesifically about radio astronomy. The antennas (radio telescopes) 
used in radioastronomy are not necessary look like paraboloid reflector.
Their design depend on the wavelength. For example in meter and decimeter 
wavelength the radiotelescope looks like TV antennas.
Specifically the mirror of the paraboloid radiotescope should be built of
the metal of good conductivity (at least its surface). 
Of cource radioastronomers can observe at the day time.

>What advantage radioastronomy has on optical astronomy?

Radioastronomy provdes scintist another information abot the object.
Imagine that your eyes can see only green colour. Then the moon for example 
looked diferentely. I would say you would have more limited information 
about the moon in comparison with another man who is sencitive to the whole 
optical band.

Additionally there are some objects that emmit in radio but does not emmit in 
optics. Such objects simple have not existed for human being.

There are many books about Radio astronomy.
In particular you can look Radio Astronomy by John Kraus.

You can ask more the people in France: The Paris observatory has the
radio astronomy deprtment; there is an radio astronomy observatory at
Nance, and milimeter radio observatory IRAM.


Leonid Kogan



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>From owner-daip at kochab.cv.nrao.edu Thu Apr 27 11:45 MDT 2000
Date: Thu, 27 Apr 2000 16:51:01 +0200
From: Famille Dreyfus <fdreyfus at club-internet.fr>
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Hello,
I'm a french student and I'm doing a research on radioastronomy. I'd
like to ask you some questions:
With what stuff the mirror of the radiotelescope is made of?
Can you observe during the day?
What advantage radioastronomy has on optical astronomy?
Can you send me some documents about radioastronomy???

Thank you very very much....
Guillaume Dreyfus
8 rue Danton
93310 Pré St Gervais FRANCE
fdreyfus at club-internet.fr


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