Besides the Earth and Mars, which planets are suitable for human habitation?

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European astronomers announced on April 24, Eastern Time, that for the first time they had discovered a planet outside the solar system that may be suitable for human habitation. There may be oceans and life on this planet.

This planet has a mass about five times that of the Earth, is 20 light-years away from the Earth, and orbits a red dwarf star called "Gliese 581", so it was named "Gliese 581c". Among the approximately 200 extrasolar planets discovered so far, Gliese 581c is the smallest one. Additionally, its orbit is within the "habitable zone," where surface water and life could exist if other conditions are right.

Gliese 581c was discovered by a team of 11 European astronomers, who have written a related paper and submitted it to the Journal of Astronomy and Astrophysics. However, Stephane Udry, an astronomer at the Geneva Observatory and the lead author of the paper, said that it is not yet possible to conclude that liquid water exists in Gliese 581c. Sara Seager, a planetary expert at MIT, said: "If Gliese 581c had an atmosphere thicker than Venus, liquid water would be too hot to exist."

Two years ago, astronomers discovered a planet with a mass similar to Neptune in the Gliese 581 system. After that, astronomers discovered a suspected planet in the "Gliese 581 system" with a mass eight times that of the Earth. The discovery of the new planet means that Gliese 581 will become the first choice for human space navigation in the future. Dimitar Sasselov, an astronomer at the Harvard-Smithsonian Center for Astrophysics, said: "This new planet is only 20 light-years away from Earth, and we are fully capable of reaching it."

In their search for Gliese 581c, Udry and his team used a 141-inch-diameter spectroscopic telescope at the European Astronomical Observatory. Previously, the smallest extrasolar planet discovered by astronomers was six times the mass of Earth. The discoverers were Geoff Marcy of the University of California, Berkeley, and Paul Butler of Carnegie University. Butler).

Gliese 581c orbits its host star, Gliese 581, every 13 days at an orbit about 7 million miles away. According to a planetary model drawn by Sutheroff and colleagues, Gliese 581c is about one and a half times the size of Earth and is made mostly of rock and water. He said: "The most exciting thing is that the new discoveries tell us that this type of planet has many unique properties. Due to billions of years of geological movements, this type of planet may be more suitable for life than the Earth. U.S. Aerospace The agency's upcoming Kepler mission may discover hundreds of similar planets. "The distance between Gliese 581c and its host star is much smaller than the distance between the Earth and the Sun, but because Gliese 581 is only one percent as bright as the Sun, it is 7 million." The distance of miles does not affect the habitation of life. Udry said Gliese 581c's temperature depends on its albedo. Using Earth and Venus as reference, he expected Gliese 581c's surface temperature to be between 0 and 40 degrees Celsius.