# The Sun's Mysterious Brother: In Search of Lost Celestial Bodies
In ancient Chinese myths and legends, Hou Yi shot down nine suns, leaving only the one we live in now. However, scientists tell us that there may be hundreds of millions of "suns" in the universe. So, where did these other suns go? Were they really shot down by Hou Yi? Let's explore this amazing topic together.
## 1. The "Sun" in the Universe
First of all, we need to understand what the "sun" is. In our daily lives, we usually understand the Sun as a huge star located at the center of the solar system that provides us with light and heat. However, in astronomy, the definition of "sun" is much broader. Any star in the main-sequence phase can be called a "sun" as long as its mass, temperature, and brightness are similar to our own sun.
It is estimated that there are about 100 billion of these stars in our galaxy. And in the observable universe, there may be more than 10 billion galaxies, each containing hundreds of millions of stars. Therefore, even if each star is named "sun", there are still countless "suns" in the universe waiting to be explored and understood.
## Second, the life cycle of the sun
Every "sun" has its life cycle. They form from clouds of gas and dust, and after millions of years of nuclear fusion reactions, they eventually deplete the hydrogen fuel at their core, entering the red giant stage. In the process, they may undergo supernova explosions or turn into white dwarfs, neutron stars, or even black holes.
Many of these stellar evolutions have been observed in our Milky Way. For example, our immediate neighbor, Sirius, is a star that is about to enter old age. In the next few million years, it will expand into a red giant star whose outer layers could swallow our Earth.
## 3. The Lost Suns
So, where do the "suns" that have reached the end of their life cycle go? Some of them have become white dwarfs or neutron stars, floating quietly in the universe. These dense celestial bodies, despite their small size, have a considerable mass. For example, UImas, the largest white dwarf star in our Milky Way, is 1.4 times the mass of the Sun, but its diameter is only the size of Earth.
There are also "suns" that have undergone supernova explosions and turned into black holes. These mysterious celestial bodies have an extremely strong gravitational pull that can attract and devour everything that approaches it. About 20 such black holes have been discovered in our galaxy.
However, there are many more "suns" that have disappeared into the depths of the universe. When a star runs out of fuel, its outer layers may be ejected to form a planetary nebula. These nebulae are made up of gas and dust, forming a beautiful sky landscape. Over time, however, these nebulae will gradually dissipate into the universe, leaving behind only a lone white dwarf or neutron star.
## Fourth, Hou Yi's Arrow and Scientific Explanation
The story about Hou Yi shooting down nine suns is just a fable that is used to explain the changing of seasons and the importance of agriculture. Scientifically, we know that the Earth's orbit has not changed because of Hou Yi's arrow. The movement of the earth around the sun is determined by the law of gravitation, which is an objective law of nature.
However, this story provokes us to think about the "sun". Each "sun" has its life cycle, going through the process of birth and death. Just like humans, we all have our own life course. We should cherish every moment, because time is passing, like those "suns" that disappear.
## V. Conclusion
In general, the stars known as the "lost sun" have not really disappeared. They have simply entered a new life cycle stage, or have been transformed into other types of celestial bodies. These stories of the "sun" teach us a truth: every life has a value and meaning, no matter how it ends.
At the same time, the story reminds us that our planet and solar system are fragile. We need to protect our homes and cherish every beautiful moment of sunrise and sunset. Because in this vast universe, we have only one earth and one sun.
Finally, let us once again thank those "suns" who provide us with light and heat. Whether real or legendary, they are an important part of our lives. Let's explore this amazing universe together, look for those lost "suns", and cherish every moment we have.