Frank Coulter
Pauanui Seashore, New Zealand
The vary of colours or wavelengths {that a} telescope can observe relies on the design of each the telescope itself and the cameras hooked up to it.
As an illustration, if you happen to’re constructing a telescope that can observe principally in infrared, normally the mirror is coated in silver or gold. For the mirrors of telescopes designed to watch in each optical and infrared, aluminum, which displays gentle pretty nicely over a variety of wavelengths, is a more sensible choice.
Mirrors in X-ray telescopes are normally coated with gold or iridium. However there’s an issue: If you happen to goal a mirror immediately at an X-ray supply, the photons (gentle) received’t be mirrored — they may both undergo the mirror or get absorbed. To unravel this, mirrors in X-ray telescopes are formed like a funnel. This fashion, the incoming gentle grazes the mirror at a really shallow angle, like a stone skimming on a lake, permitting devices on the backside of the funnel to catch the sunshine.
The detectors that register the sunshine captured by a telescope are additionally tailor-made to totally different wavelengths. Many detectors are created from semiconductor supplies, in order that when gentle hits the detector, it releases electrons, which we then measure and translate into a picture. Completely different semiconductor supplies reply to gentle with totally different energies and due to this fact totally different wavelengths.
Lastly, we are able to additional prohibit the wavelengths we observe by placing a filter in entrance of the detector. A filter is only a piece of glass that solely lets by way of sure wavelengths. Astronomical cameras normally have a number of filters mounted on a wheel, and astronomers can then choose which one they wish to use to make their observations.
It could seem to be loads of work, however seeing the cosmos by way of each attainable wavelength is vital for deepening our understanding of the universe we inhabit.
Juan Carlos Muñoz-Mateos
European Southern Observatory Media Officer, Garching, Germany
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