If you are into radio astronomy or maybe are just starting to learn about it, you most likely have come across the words “radio telescope”. But you might wonder, what is it? What does a radio telescope do and how does it work?
Just like how a TV picks up signals to supply the daily dose of our favorite show, a radio telescope picks up signals from sources from the universe that are not visible to the eyes. These signals can come from distant stars, galaxies, black holes, and other astronomical objects that are vital for exploring and understanding the universe.
What does a Radio Telescope Do in Radio Astronomy?
A radio telescope is the main observing equipment for radio astronomy that collects radio waves emitted by cosmic radio sources, amplifies them, and makes them available for analysis. These waves are converted into electrical signals that are processed to create images of the astronomical object.
Radio telescopes are capable of listening to a wide range of wavelengths, but are specially designed to detect and examine the longest wavelengths ranging from 1mm to over 10 meters long which is not possible with an optical telescope.
Parts of a Radio Telescope
A radio telescope, in its simplest form, consists of three main components: an antenna, a receiver, and a recorder.
An antenna is used to collect incoming radio waves and varies in size and shape depending on the frequency range the instrument is designed to collect. The most basic type is the metal dipole antenna, which is what you often see on cars that are used to pick up radio waves from broadcasters. However, the most powerful and versatile type — the parabolic dish antenna– can be found in radio telescopes and can bounce several wavelengths at once. This type also tends to be big in size in order to detect faint radio waves from space.
The radio signals are channeled by the feedhorn into a receiver placed directly at the focal point of the dish reflector. Since cosmic radio sources are extremely weak, radio telescopes should have the most sensitive receivers. However, this also makes them susceptible to receiving waves coming from electronics. To reduce this noise and avoid swamping the incoming signal, receivers are kept cool at 16 degrees above absolute zero.
The receiver amplifies the incoming signal about a million times and carries it along the feed support structure to the recorder where it can be stored and analyzed.
The performance of a radio telescope can be affected by several factors. For example, the dish’s surface is extremely critical. Any bulge, warps, and irregularities in the parabola will disperse the tiny waves away from the focus and will result in a loss of information.
Interferences are another important factor to be considered. Man-made equipment such as cellphones, computers, and other objects that produce radio emissions can interfere with signals coming from space. In order to avoid this, radio telescopes are built in remote, radio-quiet locations away from society.
What is Radio Interferometry?
Radio interferometry is the scientific process of using signals from multiple radio telescopes to create an image of the cosmo. This is a powerful approach that allows us to observe faint emissions that would otherwise be too weak for individual antennas to detect alone, and allows us to create detailed images of the universe with precision and accuracy. As a result, radio interferometry has been used by astronomers over the years to provide insights into objects and phenomena that were previously unobtainable with traditional telescope techniques.
Radio Telescopes in the World
The Arecibo Radio Telescope located in Puerto Rico was the world’s largest single-dish radio telescope. It was built from 1960-1963 into a large limestone sinkhole with a diameter of 305 meters. It was used to map the surface of Venus, and also played a role in the discovery of significant discoveries pulsars and binary quasars. The Arecibo radio telescope led to many significant discoveries
The Very Large Array (VLA) is an example of interferometry located in New Mexico that consists of 27 radio antennas working together as one instrument, and is the most widely-used radio telescope. The array is able to map large-scale structures of gas and molecular clouds, and has been used to study everything from our Sun to distant quasars billions of light years away.
ALMA (Atacama Large Millimeter/submillimeter Array) operates with 66 radio antennas working together to study light that straddles the boundary between radio and infrared from some of the coldest and most distant objects in space. Located in the high desert of northern Chile at 5000 meters high, its dry climate and extreme elevation provide the appropriate conditions for detecting and collecting faint cosmic signals.
What a radio telescope does is invaluable to the science of radio astronomy. It is a powerful astronomical tool that has led us to some of the most significant discoveries in astronomy. They have played a significant role in the development of astronomical knowledge and continue to provide important insights into the nature of the universe.