How to study the stars?

The city sky, in truth, is very boring. If you look at these dark patches of sky between the houses, you can see the constellation Ursa Major or Orion's Belt. But wait. Take another look at this piece of sky and close it with your thumb. How many stars behind it? Ten? Twenty? Another guess? If you look at such a piece of sky with the Hubble telescope, instead of these luminous points you will see spots. This is not a star. These are galaxies. As our milky way. There are billions of such galaxies. And more than a thousand of them are hidden under your thumb.
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Looking at the city sky or even at the starry sky outside the city, it is impossible to see how large the Universe really is. Here is the Universe, what astrophysics see it. There are more stars in it than sand grains on Earth.
Looking at the starry sky, you join the most ancient science in the history of mankind. People began to study the heavens before navigation, agriculture, perhaps even language. At the same time, astronomy, unlike other sciences, uses only the method of observation - after all, we cannot control the parameters of our experiments while sitting in the laboratory. Our best technology can deliver humans to the moon or probe to the edge of the solar system But these distances are negligible compared to the gaping interstellar space.

So how do we know so much about other galaxies; about their composition, quantity or even about their existence?

Let's start with the fact that first of all we will see by looking into the night sky - the stars. We are interested in their properties: what they consist of, their density, size, age, their distance from the Earth. Believe it or not, this information can be extracted from the light that we see in the sky.

We can decipher what the light of the stars tells us, turning it into a rainbow. When you see a rainbow on Earth - in fact, you look at the light of the Sun, which, passing through water droplets in the atmosphere, decomposes into a spectrum of colors that it consists of. To study the light from other stars, we can create a rainbow, using instead of water drops special tools for its refraction.

In the resulting spectrum, we see something strange - dark bands. These bands are characteristic prints of atoms. Different atoms of the solar atmosphere absorb light of a certain wavelength; the degree of absorption is determined by the number of such atoms.

So, by measuring the amount of light in these bands, we can determine not only which elements are present in the solar atmosphere, but also their concentration.

In the same way, we can study other stars: create a rainbow, look at what is missing, and determine which elements we are dealing with. Bingo! Now it is clear what the stars consist of.

But we are not limited to the long visible waves. Remember the radio waves. Thanks to them, you can listen to your favorite radio in your car, but they can also move in space almost seamlessly. Radio waves that have come to us from afar carry information about the earliest period in the history of our Universe - several thousand years after the Big Bang.

We can also study infrared light that emit colder objects in the universe, such as clouds of gas or dust. And the ultraviolet radiation of hot stars, recently formed from such clouds.

The study of waves of different lengths allows us to make a more complete picture not only of one specific object, but also of the whole universe. To do this, scientists use different types of telescopes that can capture from infrared to ultraviolet and x-rays; from giant radio telescopes to huge silver mirrors and satellites that capture light that cannot penetrate the Earth’s atmosphere. Astrophysicists not only see billions of stars among billions of galaxies in the universe. They hear, feel and feel them through different channels, each of which conveys its message. But the beginning of everything is light - visible and not visible. Want to unlock the secrets of the universe? Just follow the light.