Radio telescopes are astronomical observation instruments capable of capturing a wide range of radio electromagnetic waves.
What are radio telescopes?
Radio telescopes are astronomical observation instruments capable of capturing electromagnetic waves not visible to the naked eye : radio waves .
Some astronomical structures, such as distant galaxies , stars , and black holes , emit a large amount of radio waves. These waves are not captured by lenses, as in conventional telescopes.
The first observation of radio waves from astronomical objects occurred in 1932, at Bell Telephone Laboratories, and made possible the discovery of several astronomical structures invisible to optical telescopes , such as quasars and pulsars.
The waves captured by radio telescopes are called radio waves or Hertzian waves , in honor of the physicist Heinrich Hertz. These waves occupy a vast range of the electromagnetic spectrum . Their frequencies are lower than infrared waves, ranging between 300 GHz (3.0×10 11 Hz) and 3 kHz (3.0×10 3 Hz). They propagate in vacuum with the speed of light (approximately 3.0×10 8 m/s). Here are some of its features:
- Compared to other electromagnetic waves, they have the longest wavelengths and the lowest frequency and energy;
- Radio waves are considered non-ionizing radiation , as they do not have high enough energy to damage DNA molecules by removing electrons or breaking chemical bonds;
- They are widely used in telecommunications media, such as television, radio and cell phones. Despite this, radio telescopes are calibrated to detect frequencies different from those used by these equipment.
The radio waves produced by cell phones are a few billion times more intense than the radiation from most distant stars observed in radio telescopes.
Operation and characteristics of the radio telescope
Unlike optical telescopes , the radio telescope uses a large parabolic antenna to capture radio waves. These antennas act as large mirrors for radio waves.
The size of the antennas depends on the frequency of the radio waves that will be observed. This size is quite variable and can reach 576 m in diameter, as in the case of one of the largest radio telescopes in the world, RATAN-600, located in Russia:
RATAN-600 Telescope, one of the largest radio telescopes in the world*
Radio waves travel enormous distances to reach the antennas of radio telescopes. When they arrive, they are reflected towards a wave receiver located at a point called a focus .
A radio telescope’s ability to distinguish details in astronomical objects is linked to its angular resolution. This property depends on the antenna area. For a radio telescope to have a resolution similar to that of an optical telescope, its area must be even larger .
In order to solve this type of problem, associations are made with several smaller radio telescopes, but in large areas , which work as a single giant radio telescope. The mechanism is simple: when using two or more radio telescopes spaced apart, the radio waves incident on each of them will arrive with a small time difference. This time interval allows other image perspectives of the same object.
As a result, a large increase in angular resolution is obtained, allowing the observation of very distant or dimly lit objects.