Secrets of the Cosmos: Universe Composition and Formation

The Vastness of Space: Galaxies, Stars, and Dark Matter

The universe is a vacuum containing billions of galaxies. In turn, each galaxy contains billions of stars, planets, and nebulae. In addition to visible objects, there is matter we cannot see: the so-called dark matter. Astronomers currently estimate that stars and planets occupy only 10% of the universe, while 90% is composed of dark matter.

Elemental Composition of the Cosmos

The universe is primarily made up of light elements:

• 75% Hydrogen
• 20% Helium
• 5% Other elements

This composition was determined by comparing the spectrum of white light with the spectrum of sunlight.

Defining a Galaxy

A galaxy is a massive cluster of stars, planets, gas, and dust. It typically has a supermassive black hole at its center. In the case of the Milky Way, the central black hole is Sagittarius A*, and our star is the Sun.

Discovery of Exoplanets

Two astronomers discovered the first planet orbiting a star other than the Sun. They found that stars sometimes lost some brightness, which occurred because exoplanets were passing in front of them (known as the transit method). The advances in this field are so rapid that the figures regarding discovered exoplanets are overwhelmed in a matter of days.

The Formation of Our Sun

The process of solar formation begins with a catastrophic event:

1. A supernova explodes, generating a powerful shock wave.
2. This shock wave approaches a nebula and compresses it, causing the nebula to collapse.
3. In the center of the collapsing nebula, particles become closer to each other, leading to increased collisions.
4. Due to these collisions, the center of the nebula is heated intensely.
5. Once the temperature reaches 10 million degrees Celsius, hydrogen nuclei move at tremendous speed and can fuse to form helium, releasing vast amounts of energy.

Through this process, Our Sun was born.

Evidence of Cosmic Expansion: The Doppler Effect

We know that galaxies are receding from each other because their spectral lines appeared displaced (redshifted) from their expected position. This phenomenon is called the Doppler effect. If galaxies are moving away from each other, it is conceivable that in the past they were closer, suggesting that in principle, all matter was concentrated in a very small area.

The Point of No Return

This refers to the minimum safe distance required so that surrounding stars or objects do not fall into a central gravitational body, such as a black hole.

Confirmation of the Big Bang Theory

While working on a new type of commercial antenna, scientists found that they received very weak radiation coming uniformly from all points in the universe. This signal was extremely weak, suggesting it originated from something very distant. This phenomenon is known as the Cosmic Microwave Background (CMB) radiation, providing strong confirmation of the Big Bang theory.