Cosmically simple: stars, black wholes etc.

We live in an amazing time when space missions are being sent to the stars, humans are beginning to explore the moon, and robots are becoming full-fledged crew members. But there are still simple questions that we will give simple answers to today.

Cosmically simple: stars, black wholes etc.

Why is it dark inside black holes?

Such mysterious space objects are complex on the one hand, but rather simple on the other.

Researcher Vyacheslav Dokuchaev explains that a “black hole” is commonly referred to as a tightly compressed massive object. It can be joined stars, which, due to their small size, do not let light through. Scientifically speaking, the point is that the second space velocity on the surface of this body is greater than the speed of light, and therefore the photons of light cannot escape from there.

“Black hole” is commonly referred to as a tightly compressed massive object.
Black holes are an important object of basic research. Their study is advancing thanks to advances in space research technology. In 2017, for example, U.S. scientists won the Nobel Prize for a discovery that helped investigate black holes. They discovered gravitational waves. And then physicists used sophisticated laser interferometers to record black hole mergers generating gravitational waves. These waves were registered, and the uniqueness of the signal suggests that only black holes can provide such a signal form.

The world scientific community recognized the importance of the result of American scientists, and a year after the discovery, the researchers received a prize.

The idea of mysterious black holes has become more accurate over the past 40 years. This happened after the discovery of quasi-stellar objects, quasars. These are the most powerful emitters in the universe, as well as accreting black holes with masses millions and billions greater than the Sun. They are located at the center of distant galaxies.

What color is the Sun?

The Sun is not actually yellow but white. This is because of its temperature. It is 5780 kelvin and makes the star glow with this color.

If you look closely, you can see other colors in the sky – cooler stars are red and hotter stars are blue. As soon as the sun’s rays “touch” the Earth, they change their hue to a yellowish color.

The sun emits all the colors of the visible spectrum

It goes like this. Particles of light, called photons, at the lower end of the visible electromagnetic spectrum (that’s yellow, orange, red, they have longer wavelengths) scatter harder than photons at the upper end of the spectrum (violet, blue, green – shorter wavelengths). Earth’s atmosphere transmits longer wavelengths from the yellow-red part of the spectrum, as if “filtering out” light.

There is another explanation for the “yellowishness” of the Sun. The tint is due to pollution in the atmosphere, which enhances the scattering effect. That’s why our star appears white in the desert with a clear and cloudless sky.

But what happens at sunrise and sunset when the Sun “blazes” with fiery colors?
It’s all about location. The Sun is closer to the horizon, so the light has to penetrate more atmospheric molecules. The photons of the blue-green spectrum scatter even more, while the low-energy yellows, reds, and oranges stay in place.

And it is possible to see the real color of the Sun only from space, because there photons simply have nothing to interact with.

Why do stars flicker?

In fact, the twinkling is not peculiar to the stars themselves. It is because of the Earth’s atmosphere. The rays of the stars must pass through it, and then they are noticed by the inhabitants of the Earth. And above the restless gas shell of the planet through which we view the Universe, there is no twinkling of stars: they shine with a calm, steady light.

Surely everyone has noticed the flickering of distant objects when, on hot days, the ground is very heated by the Sun. The cause of their flickering is the same. And starlight penetrates not a homogeneous immovable medium, but gas layers of different temperatures and densities. In this atmosphere there are many optical prisms, convex and concave lenses, which endlessly change their positions. Being in such “labyrinths”, light rays in them undergo numerous deviations from the straight path, now concentrating, now scattering. Therefore, both the brightness and the coloring of stars change from time to time.

This property of the atmosphere hinders astronomers during observations of the sky, so great importance is given to telescopes that are outside the Earth’s atmosphere. For example, Kepler and Hubble.

This is important because the absence of the atmosphere, first, does not distort or weaken the light from the stars, and secondly, makes measurements more accurate. Thus, the Kepler telescope helped scientists discover many exoplanets that cannot be seen from Earth. Another important area of modern science that compensates for such atmospheric distortions is adaptive optics

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