According to a new study, scientists believe that alien life could possibly exist on nearly 90% of Earth-size planets found in the universe.
According to a team at the American Georgia Institute of Technology, it’s the tilt of the planet that determines if it can sustain life. If the planet’s tilt is stable while it is orbiting its sun, it would have steady and predictable seasons that would allow life to survive there. In fact, dual-star systems are quite common and that allows planets to have an even more stabilized tilt.
The team believes that 87% of exo-Earths would have the same type of axis tilts as ours, which is essential in order for life to thrive there. While the mild changes to Earth’s tilt have helped the evolution of life, the drastic variations to Mars’ tilt have had the opposite effect as it helped to destroy the atmosphere.
The team studied planets in the “habitable zone” of star systems, including stars “A” and “B” from Alpha Centauri which is only four light years away from us. “We simulated what it would be like around other binaries with multiple variations of the stars’ masses, orbital qualities, and so on,” explained principal investigator Billy Quarles, adding, “The overall message was positive – but not for our nearest neighbor.” While there haven’t been any confirmed exoplanets discovered around stars “A” or “B”, if there were any, they would probably be uninhabitable.
Even though Earth has had periods of heat waves and ice ages, our climate has pretty much been steady for millions of years because of the tilt of our axis. In fact, the orientation of Earth has only changed slightly in the last 41,000 years – between 22.1 and 24.5 degrees. We can thank our Moon for our stability because without it, the gravity from our planetary neighbors (Mercury, Venus, Mars and Jupiter) would completely destabilize our tilt. “If we didn’t have the moon, Earth’s tilt could vary by about 60 degrees,” Dr. Quarles said, adding, “We would look maybe like Mars, and the precession of its axis appears to have helped deplete its atmosphere.”
If an Earth-like planet is in the habitable zone of a star system and has a steady axis, alien life is definitely a huge possibility, especially in binary systems. “Multiple-star systems are common, and about 50% of stars have binary companion stars,” stated co-investigator Professor Gongjie Li, adding, “So, this study can be applied to a large number of solar systems. Single-star solar systems with multiple planets like ours appear to be rarer.
Li went on to say, “In general, the separation between the stars is larger in binary systems, and then the second star has less of an effect on the model of Earth.” Their findings were published in The Astrophysical Journal and can be read in full here.