Radio Telescopes
A radio telescope is a telescope that helps scientists ‘see’ the universe using radio waves (1 mm to more than 10,000 km in wavelength).
These telescopes collect faint radio waves coming from deep space, and with the help of other equipment focus and amplify them for scientific study.
Radio telescopes can detect radio waves from a number of celestial objects, such as stars, galaxies, and black holes.
They are ground-based, and not in orbit, because they are usually quite large.
This is because the size of the antenna – the dish-like structure that detects the waves – is proportional to the wavelength being tracked.
In fact, the most common radio telescopes have a parabolic dish antenna.
Due to its curved shape, the radio waves hitting the dish bounce to a point called the focus, where a receiver collects them.
Dish antennas collect many different wavelengths at once, so scientists often use receivers picking up multiple wavelengths at once.
Radio Telescopes
Because of their large wavelength, radio waves can travel long distances without interruption, making them ideal to catch glimpses of stars behind dust clouds, for example.
But the longer they travel, the weaker they get.
So telescopes often try to maximise their signal collection area and use amplifiers to increase their strength.
One of the biggest radio telescopes in the world today is the FAST instrument in China, with a 500-metre-wide dish.
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