Being visual species, astronomy for a long time meant to gaze up and study the visible objects in the sky through light, which led to several important discoveries about our world. But because not everything emits light and is visible to the eyes, astronomers have found new methods and instruments to observe the “hidden” cosmos through what is now known as radio astronomy.
What is it? How does radio astronomy work? In this article, we’ll answer these questions and more about this fascinating science so read on and enjoy.
What is Radio Astronomy?
In 1932, Karl Jansky made the first radio astronomy observation while investigating static that was interfering with transatlantic radio transmissions. He found that the interference was coming from thunderstorms and sunspots, but he also discovered something new – faint emissions coming from the center of our Milky Way galaxy. This discovery laid the foundation for the now very important science of radio astronomy.
Radio astronomy is a crucial tool that has been used to probe the secrets behind some of the most fascinating objects in the cosmos that would otherwise be invisible to us through the radio waves that they emit.
Just as optical astronomy has been essential in observing objects that emit visible light, radio astronomy has been vastly important in studying the origins of the universe and the development of solar systems.
How Does Radio Astronomy Work?
Often confused with something that we can “hear”, radio waves are not the same as sound waves, but are actually a form of radiation in the electromagnetic spectrum.
The electromagnetic spectrum is a continuous range of all possible frequencies of electromagnetic radiation that produce energies traveling through space in the form of waves, which also includes the visible light that we see with our eyes, microwaves, ultraviolet light, infrared light, X-rays, and gamma rays.
Radio waves are just a very tiny part of the electromagnetic spectrum that have the lowest frequencies and longest wavelengths that can range from 1mm long to a size larger than our planet.
Nearly all types of astronomical objects give off some radio radiation, and astronomers use these radio waves to further study these objects and the universe. Pulsars, quasars, radio galaxies, and certain nebulas are among the most powerful emitters.
A radio telescope, in a nutshell, is the main equipment used to study radio astronomy and is designed to receive radio waves from space. But what does a radio telescope do?
Just as optical telescopes use visible light, radio telescopes use radio waves to view and study distant galaxies and astronomical objects, from stars and planets to black holes. They are designed to detect radio-frequency radiation with wavelengths ranging from 1 millimeter long to over 10 meters long.
Because cosmic radio sources are often weak, radio telescopes are generally huge, ranging from hundreds of meters across.
Radio telescopes generally are built with two basic components:
- Dish antenna that collects incoming radio waves in all directions
- A radio receiver that amplifies signals arriving from specific directions. The sensitivity of receiver affects the telescope’s ability to measure sources of radio emission
These telescopes are equipped with receivers that can detect faint signals from distant galaxies and stars that are then converted into images analyzed by astronomers for further research or study. A wide range of frequencies can be detected by these radio telescopes, making them versatile tools in the field of astronomy.
In 2020, NASA’s Jet Propulsion Laboratory (JPL) proposed the Lunar Crater Radio Telescope (LCRT), a moon-based telescope that will be built inside a lunar crater with the primary purpose of detecting long-wavelength radio signals from the universe’s Dark Ages.
It is currently in its early stages of planning and development, but it is expected to open up groundbreaking discoveries in radio astronomy.
Radio interferometry is a technique that uses signals from multiple radio telescopes to create an image of the cosmos. This approach permits us to observe faint emissions that would otherwise be too weak for individual antennas to detect alone.
The data collected is then combined through a process called correlation which provides 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.
The Very Large Array (VLA), an example of interferometry located in New Mexico, is a system consisting of 27 radio antennas that work together as one instrument, and is the most widely-used radio telescope in the world.
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.
Radio Astronomy Discoveries
One of the most significant radio astronomy uses is that it helps us explore the universe in a way that other forms of astronomy cannot. It is an incredibly valuable tool that allows us to see further and beyond what is visible, which has led to many groundbreaking discoveries about the universe and its inhabitants.
For example, in 1963, radio astronomy was used to discover the first-ever known quasar. Quasars are powerful, extraordinarily bright objects that reside in the centers of galaxies and emit staggering amounts of radiation.
Quasars were first detected by their radio emissions, which led astronomers to believe that they were distant starbursting galaxies. However, further study with radio telescopes revealed that quasars are actually quite different from other types of astronomical objects.
Pulsars are another major finding made using radio astronomy. Pulsars are spinning neutron stars that emit a regular pattern of pulses similar to a lighthouse.
In 1967, radio astronomers Jocelyn Bell and Antony Hewish discovered the first pulsar while searching for quasars using a radio telescope. The discovery of pulsars has since been instrumental in understanding extreme astrophysical phenomena such as black holes and gamma-ray bursts.
Radio Astronomy: Advantages vs. Disadvantages
Radio Astronomy Advantages
- Radio astronomy made it possible to detect other galaxies beyond the center of our galaxy along the line of sight because radio waves travel unimpeded by dust in our galaxy, which is impossible to view with visible light and optical telescopes.
- Radio waves are not affected by the Earth’s conditions (weather, clouds, etc.) in the same way that visible light is, which allows astronomers to get a clearer view of space using radio telescopes.
- Some cosmic objects emit radio waves stronger than any other form of radiation. Radio astronomy through radio telescopes allows for a deeper and more complex study of these objects.
Radio Astronomy Disadvantages
Radio astronomy, despite the discoveries and breakthroughs it brought, also has its disadvantages, with the resolution being one of its biggest drawbacks.
Due to the fact that radio waves are much longer than visible light waves, radio telescopes generally are built much larger and more expensive than optical telescopes in order to produce a good resolution. This is also why interferometry is much more common in radio astronomy.
Radio astronomy also faces problems with what are called interferences. In the same way that optical astronomy can be affected by light pollution, man-made interferences such as communication satellites, aircraft, and cell phone towers can mask signals from natural radio sources and make radio observations more difficult to conduct.
As a result, radio astronomers often have to carry out their observations from remote locations away from major cities.
Astronomy has come a long way, from optical astronomy which helped us understand what is visible to the eye, to radio astronomy which allowed us to see the “invisible”. Radio astronomy is a powerful tool that has expanded our understanding of the universe in many ways and despite its own share of challenges, radio astronomy has made a number of important discoveries and continues to play a crucial role in our understanding of the Universe.