How do astronomers listen to space?

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In 1933, an engineer named Karl Jansky accidentally discovered that radio waves come not only from man-made inventions but also from natural materials in space. Since then, astronomers have been building better and better telescopes in the search for cosmic radio waves, trying to learn more about where they come from and what they can tell us about our universe. While scientists can learn a lot from the visible light they detect with regular telescopes, objects like black holes, stars and planets forming and dying, and much more can only be detected with radio telescopes. Together, telescopes capable of picking up different types of waves—from radio waves to visible light waves and gamma rays—paint a more detailed picture of the universe. But is listening to the stars as simple as it might seem at first glance?



Visible light
When we look at the night sky, we see the bright lights of stars. If you live in a dark area far from cities, you can observe thousands of such objects. At the same time, the individual points that you see are nearby stars. More than 200 billion of these celestial bodies exist in our galaxy alone. Outside the Milky Way, according to various estimates, there are at least 100 billion galaxies, each with its own 100 billion stars. Almost all of these stars are invisible to our eyes.

The visible light that the human eye perceives is only a tiny part of what astronomers call the “electromagnetic spectrum.” Photons with higher energy are ultraviolet radiation, X-rays, and gamma rays (gamma rays have the highest energy). Photons with lower energy are infrared and radio waves (radio waves have the lowest energy).

The electromagnetic spectrum includes gamma rays, X-rays, ultraviolet radiation, infrared radiation, microwaves, and radio waves. Since human eyes can only perceive visible light, we need special telescopes to capture the rest of this "spectrum" and then convert it into images and graphics.

What is a radio wave?
Light is made up of tiny particles called “photons,” which can lithuania number data behave both as particles and as waves. In visible light, photons have a moderate amount of energy, but as they get more energy, they turn into ultraviolet radiation, which we can’t see but can easily cause sunburn. With more energy, photons turn into X-rays, which pass right through us. But with even more energy, they turn into gamma rays, which come from exploding stars.

In cases where photons have very little energy, scientists talk about infrared radiation, which we feel as heat, and photons with the lowest energy are called “radio waves.” Interestingly, radio waves come from very strange places in space — the coldest and most distant galaxies and stars. They tell us about those corners of the Universe that we would not even suspect if we used eyes or telescopes that perceive only the visible light spectrum.

Pioneers of radio astronomy
Interestingly, the world’s first radio astronomer was actually an engineer. In 1933, Carl Jansky was working on a project for Bell Laboratories, a New Jersey laboratory named after Alexander Graham Bell, who invented the telephone. They were developing the first telephone system that would work across the Atlantic Ocean. But when people first tried to call using this system, they would hear a hissing sound in the background at certain times of the day.