Non-optical telescopes Flashcards
What is collecting power of a telescope proportional to?
collecting area or diameter squared
What does is it the collecting area of?
Objective mirror/dish
For UV it is the size of the opening through which the X-Rays can enter
Do X-Ray telescopes have higher or lower collecting power than other Telescopes?
lower
Why does a bigger dish mean better collecting power?
Collects more energy in a given time. This means a more intense image
Higher collecting power means a more intense image, so the telescope can observe ……… objects
fainter
In what ways are radio telescopes similar and differences to optical telescopes??
Parabolic dish works the same as objective mirror of a optical reflecting telescope
Antenna used as detector at the principal focus instead of eye
Manoeuvrable
No equivalent to the eye lens of an optical telescope
What is the order of the components of a Radio telescope?
1) What does a preamplifier do?
Amplifies weak radio signals without adding too much noise to the signal
2) What does the second amplifier do (High-Gain amplifier)?
The signal is amplified further.
3) What does the filter do?
Filter out any unwanted wavelengths.
4) What does the computer create? How does it create it?
A computer creates a “false-colour image” of the detected radio signals. Different colours are assigned to different wavelengths or intensities to produce “false-colour images” of non-visible EM radiation.
How is the source stopped from slipping out of view of the radio telescope?
How big are radio waves compared to light?
About a million times longer
How big would a radio telescope need to be to have the same resolving power as an optical telescope?
How do scientists get around this?
A million times bigger
Linking lots of them together, data is combined to form a single image
What is used in a radio telescope instead of the polished mirror of an optical telescope?
Wire mesh
What advantages are there of using wire mesh?
Construction is cheaper and easier, dish doesn’t need to be as perfect because the longer wavelength radiation of radio waves is less affected by imperfections.
Why does the dish shape of a radio telescope have to have a precision of λ/20 ?
To avoid spherical aberration
What is the biggest problem with doing astronomy on earth?
Atmosphere stops certain wavelengths from coming through
What 2 waves can be observed on the surface of the earth?
Optical ( a little UV and a little IR)
Radio
What happens to the most of the IR radiation that gets through the atmosphere?
Absorbed by water vapour
Where is the best place to observe infrared radiation?
High and dry places E.G The Mauna Kea volcano in Hawaii
How do you detect X-rays and Ultra violet radiation?
Strap the UV and X-Ray telescopes to high-altitude weather balloons or aeroplanes
Where is the ideal place to put your telescope?
In space
How are IR and UV telescopes similar to optical reflecting telescopes?
Use the same parabolic mirror
What’s the same about UV and IR telescopes?
Both use CCDs as radiation detectors
And both use parabolic mirrors
The longer the wave length the ….. its effected by imperfections
Less
How precise does the mirror shape in IR and Radio telescopes need to be and why?
Not as precise
Because it’s has a long wavelength so is affected less by imperfections
How precise does the mirror shape in UV telescopes need to be?
More precise
Because it’s has a shorter wavelength so is affected more by imperfections
What’s the problem with IR telescopes that does effect any other type of telescope?
It creates its own infrared radiation so needs to be cooled to very low temperature using liquid helium or refrigeration units
What’s different about X-Rays compared to other EM radiation?
Don’t reflect of surfaces.
They are usually either absorbed or pass straight through it
When do X-Rays reflect?
If they just graze a mirror surface
Explain how a grazing telescope works
A series of nested mirrors to gradually change the direction of X-Rays to bring them to focus on a detector
What are X-Rays detected by?
Modified Geiger counter or fine wire mesh, modern X-Ray telescopes use highly sensitive CCD cameras.
