[Popular Science] Is the Earth the only habitable planet in the universe?

If we do a questionnaire survey: Which planet in the universe is the most habitable? Without a doubt, most people’s answer will definitely be: Earth.

If there were no cosmic rays, sufficient oxygen and suitable temperature, abundant water and rich minerals, etc., considering the habitability of the Earth from the current perspective of human beings, then there might not be a second habitable planet better than the Earth.

However, there are countless galaxies in the universe, and each galaxy contains countless stars. According to our current scientific observations, most stars in the Milky Way have their own planetary systems. How many of these planetary systems are suitable for human survival?

This is a very interesting question. In the world known to humans, the key conditions for life are the presence of energy and water. Therefore, in the area around a star with moderate temperature, if liquid water can exist on the surface of a planet in this area, we humans call it the star's habitable zone, and its boundary depends on the size and brightness of the star. For the sun, this area is roughly distributed between 0.99-1.7 astronomical units, and the earth is located at the innermost edge of the sun's habitable zone. At the same time, our Mars is also located in the sun's habitable zone.

Although Mars looks like a barren celestial body, it is the main target of extraterrestrial life exploration and the biggest hotspot in deep space exploration by various countries. In the near future, it may only be a matter of time before humans transform it into a habitable celestial body, making it possible for future humans to migrate to Mars.

At the same time, with the continuous deepening of observations by a new generation of very powerful space telescopes and the continuous advancement of more deep space exploration, humans have also discovered more and more stars with planets similar to the Earth in their habitable zones. The surfaces of these planets also allow the existence of liquid water, which provides the necessary conditions for the birth and prosperity of possible life on the surfaces of these planets.

Facing the vast universe, humans still have too many answers to explore. I believe that in the future humans will be able to walk on a new planet suitable for everyone to survive. So, let us carry forward the spirit of aerospace, ask the sky, explore the vast universe, look up at the stars, and embrace the sea of ​​stars. (School of Earth and Space Sciences, University of Science and Technology of China/Leng Wei)