Outside the solar system, at least 20 planets may be more suitable for life than Earth. The planets are slightly older, wetter, warmer and slightly larger than Earth, the researchers wrote in the September 18 issue of astrobiology. All of these factors may mean that some of these planets will be the best destinations for extraterrestrial life. < / P > < p > “we have to focus on the planets that are most likely to give birth to complex life. But at the same time, we should also be wary of being too obsessed with finding a second earth, because there may be planets that are more suitable for life than Earth, “said Dirk Schultz markucci, an Astrobiologist at the University of Washington. To date, astronomers have discovered more than 4000 exoplanets. Most of them are not habitable. Kelt-9b, for example, is very hot and its atmosphere is melting. Tres-2b, the darkest known planet, has an atmosphere temperature of 1800 degrees Fahrenheit (900 degrees Celsius). GJ 433 D, an uninhabitable planet, is extremely cold. Its discoverers say it is the coldest Neptune like planet ever discovered. < / P > < p > but there are also many planets that are “within the habitable range” from their stars, or “just right” from their stars, which can maintain a surface temperature suitable for life evolution, neither too cold nor too hot. Schultz markucci and his colleagues aim to find the most likely exoplanets to become “super habitable.”. In other words, in addition to being livable, they also have other characteristics, making them a good place for life to multiply. < / P > < p > these features include a star of the right size and longevity, especially considering that on our planet, it took 3.5 billion years for complex life to evolve and another 4 billion years for humans to emerge. The larger the planet, the larger the land mass and habitat space; a larger planet will have more gravity and thus a thicker atmosphere, which is more conducive to the survival of flying creatures, the researchers wrote. Given that there are no large areas of barren polar regions, planets slightly warmer than the earth would be more habitable, but warmer planets would also be wetter than the earth, otherwise there would be deserts everywhere. Thus, a more habitable planet might be similar to the earth that was in the Early Carboniferous 395 million years ago, when many of the earth’s continents were in a tropical rainforest climate. (modern global warming is not conducive to the survival of life on earth, not only because of the rapid change, many animals can not adapt; also because the rise of sea level will affect the infrastructure of human survival; however, a little higher temperature is essentially harmless to life.) < / P > < p > the researchers also wrote that the upgraded version of the earth may also “come with” a slightly larger moon, or a slightly closer moon, which will help stabilize the planet’s orbit and prevent life disrupting tremors. < / P > < p > the researchers then gave a set of parameters to determine whether a candidate planet meets all of these criteria. Based on these parameters, the perfect super habitable planet will orbit a K-type main sequence star (a relatively small star, which is slightly cooler than our sun, so it is also called an orange dwarf); it is between 5 billion and 8 billion years old; it is 10% larger than earth; its average temperature is 9 degrees Fahrenheit (5 degrees Celsius) higher than Earth’s; its surface is moist, land and water The oxygen content in the atmosphere is between 25% and 30%. The perfect planet will also have plate tectonics, or earth like geological processes that recycle minerals and nutrients through its crust and create diverse habitats and terrain. And it also has a moon between 1% and 10% of its own size, spinning at an appropriate distance. Of course, it is not realistic to evaluate a distant exoplanet by all these criteria. For example, we can’t calculate the size of continents on exoplanets, let alone the distribution of them. < / P > < p > but based on some measurable factors (such as star type and planetary radius), the researchers studied some objects that may meet the above criteria and have been observed by Kepler telescope. They then found 24 “Kepler objects of interest,” though not all of them were planets. Of the 24 Kepler objects of interest, two have been identified as exoplanets (Kepler 1126b and kepler-69c). Some may be false positives. They are not planets. Of the 24 objects, 9 orbit around the appropriate type of star, 16 are in the appropriate age range, and 5 are in the appropriate temperature range. Only one Koi 5715.01 meets the above three conditions. But the real surface temperature of the planet depends on the intensity of the greenhouse effect in its atmosphere, the researchers write. All 24 possible planets are 100 light-years away. And even with our most powerful telescopes, some of the planets are too far away to study. Kepler-69c, for example, is more than 2000 light-years away, meaning it will be difficult for astronomers to look closely at it for signs of life for a long time. But Schultz markucci and his colleagues write that it’s important to find out what makes a planet “super habitable” because it’s possible to find one within 100 light-years. If such a planet can be found, it should be the first choice for us earthlings to search for extraterrestrial life in the universe. Global Tech