In the primitive age, even though cave-dwelling humans had no real knowledge of astronomy, once they learned how to think, their first curiosity arose about the Sun, planets, stars, and comets. They tried to understand the ever-changing map of the sky. As intelligence slowly blossomed, they began to reason and apply logic. This process never stopped, and in time it became possible to gain vast knowledge about space, from the Big Bang to black holes.
Thought is the true beginning. Once we begin to think, countless questions about the mysteries of the Universe arise in the mind, opening new directions for exploration. When we think about the birth of the Solar System (Galaxy), many questions arise naturally:
- In empty space, how and when did the Sun and planets come into being?
- Why are all the planets and the Sun spherical?
- Why do all planets revolve around the Sun continuously?
- If everything was created together, why does only the Sun shine like a star, while planets did not?
- Why are the inner planets (Mercury, Venus, Earth, Mars) solid, while the outer planets (Jupiter, Saturn, Uranus, Neptune) remain gaseous spheres?
- Why is there no planet between Mars and Jupiter, but instead a belt of countless asteroids?
Even the great scientists Galileo and Newton could not answer these questions. They were mainly observers of planetary motion in their own times. In 1610, Galileo used the telescope he built to observe Jupiter and its four large moons for the first time. In 1687, Newton explained the laws of planetary motion through his famous three Laws of Motion. Yet, neither could unravel the mystery of planetary formation.
In 1755, the German philosopher Immanuel Kant, applying Newton’s law of gravity, suggested that billions of years ago, dust and gas particles in space collided and combined under gravity. Small clumps grew larger and eventually merged into planets. Kant’s hypothesis turned out to be correct. Over time, modern astronomers accepted it as a scientific theory. With further research, they reconstructed the birth of the Solar System step by step.
The sequence begins with the Big Bang, about 13–14 billion years ago, which gave birth to the Universe. After the explosion, the Universe was dark for ages because light had not yet been produced. Light could only emerge once stars were born. In short, the early Universe was starless. But the matter created by the Big Bang kept spreading everywhere. After millions of years, some regions of matter condensed into stars. Suddenly, like switching on a bulb in the pitch-dark night, light appeared for the first time, illuminating space. The first birth of light in the early Universe was a great miracle!
This miraculous process has continued ever since. One by one, stars kept forming—some small, some massive—but all glowing in space. As their numbers increased, they clustered into galaxies. In this process, our own galaxy, the Milky Way, was formed. At that time, however, the Solar System had not yet come into existence.
About 8 billion years into the Milky Way’s age, new stars were still forming. Clouds of gas and dust gradually lit up with the glow of these stars, creating the bright, milky bands across the sky.
The birth of our Solar System began when, nearly 5 billion years ago, a nearby massive star exploded as a supernova. Its material spread into space at nearly 12,000 km per second, shining brighter than millions of stars combined. That star met its end, but its shockwaves rippled across many light years. Our Solar System’s raw material cloud was caught in this violent blast. Thus began a new chapter: the end of one star triggered the birth of another.
The shock compressed the hydrogen gas and dust particles of the nebula, forcing them closer. Some regions swirled more intensely, forming a great rotating disk. At its center, matter accumulated under immense gravity, pressure, and heat. Temperatures rose to about 14 million °C, igniting nuclear fusion. Hydrogen atoms fused into helium, releasing enormous energy. Our Sun was born—a natural nuclear furnace glowing at the center of the Solar System.
Meanwhile, smaller clumps of matter continued forming in the surrounding disk. Dust and ice particles collided, sticking together to form rocks, then planetesimals, then larger planetary bodies. Near the Sun, high heat blew away light gases, leaving behind dense, rocky inner planets—Mercury, Venus, Earth, and Mars. Farther away, the cold allowed gases to remain, and massive planets like Jupiter and Saturn captured enormous amounts of hydrogen and helium, becoming giant gas planets.
Between Mars and Jupiter, no planet could form because Jupiter’s strong gravity disrupted the accumulation of material. Instead, countless small bodies remained there—the Asteroid Belt.
Thus, through billions of years of cosmic processes, the Solar System we live in came into being.
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