Alien life can be more common than we thought, according to scientists.
But every extraterrestrial life in the universe tends to inhabit very different, very distant star systems, the researchers concluded.
The new study looks at the twin theories of Earth and explores how it fits into the binary star system. Unlike our own solar system, places like that have planets that revolve around two stars.
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They found that in 87 percent of the cases, the planets had to be tilted similar to Earth. That in turn is considered an ingredient for a climate that supports the birth of complex life, like us or aliens.
The star system was found throughout the universe, showing that at least some of them could function as a home for planets where alien life looked up to see two suns in the sky. Single star systems like the one we live in actually look even rarer.
"Multi-star systems are common, and about 50% of stars have binary companion stars. So, this research can be applied to a large number of solar systems," said Gongjie Li, co-researcher research assistant professor at Georgia Tech's. School of Physics, in a statement.
The researchers began by examining how the tilt of the Earth compared to the tilt of Mars. They found that our relatively mild tilt changes helped make the Earth a great place to start and develop, while far more extreme variations on Mars helped to destroy the atmosphere.
They then saw how the Earth could rise if it was located in a system known as Alpha Centauri AB, which is a neighbor of our solar system, and is a binary system consisting of two stars known as "A" and "B". The news is pessimistic in the system, offering bad news to those who plan to send spacecraft to the system in the hope of discovering alien life.
"We simulate how it happens around other binaries with many variations in star mass, orbital quality, and so on," said Billy Quarles, lead researcher of the study and a research scientist at Li's laboratory. "The overall message is positive but not to our closest neighbors."
The researchers then looked further into the universe. This finding is more positive for alien life when they look farther, because research shows that gentle variations like those on Earth are far more likely when looking deeper into the cosmos.
"In general, the separation between the stars is greater in the binary system, and then the second star has less influence on the Earth model. The dynamics of the planet's own motion dominate other influences, and the slope usually has smaller variations," Li said. "So, this is quite optimistic."
The new study, 'Obliquity Evolution of Circumstellar Planet in Sun-like Stellar Binaries', was published in the Astrophysical Journal today. It was funded by NASA's Exobiology Program.
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