Brumfield reports that a new study focuses on the axial tilt of Earth-like exoplanets in binary or double star systems. It boosts hope for complex life elsewhere … although not, these astronomers say, within the star system closest to our sun. Are we alone, or are there other intelligent civilizations in our Milky Way galaxy? In recent years, astronomers have discovered thousands of exoplanets, or worlds orbiting distant suns, some of which are potentially habitable. The growing consensus seems to be that we probably aren’t all by ourselves. Now a new study – announced by astronomers at the Georgia Institute of Technology (aka Georgia Tech) on November 20, 2019 – focuses on the axial tilt of Earthlike exoplanets in binary or double star systems. It also boosts hope for complex life elsewhere … although not, these astronomers say, within the star system closest to our sun.
The new peer-reviewed study was published in The Astrophysical Journal on November 19. The researchers found that if a theoretical twin of Earth were placed into a binary star system – where two stars orbit each other – up to 87% of them should tilt on their axes in a way similar to Earth’s. What’s more, the tilt should be as stable as Earth’s: not perfectly stable, but not wildly unstable, either. This result is significant, since Earth’s relatively steady tilt on its axis helps our world maintain a stable climate, needed for complex life to evolve.
Astronomer Gongjie Li at Georgia Tech said in a statement that multiple-star systems are common, and about 50% of stars have binary companion stars. So, this study can be applied to a large number of solar systems. Do the results mean that all exoEarths in double star systems have steady and stable axial tilts, along with a greater potential for complex life? Unfortunately, no. We need only look as far as the next-nearest star system to find a counter-example. That is, the researchers modeled an example of an Earthlike world within the habitable zones of the two primary stars in the Alpha Centauri system, only 4.2 light-years away. Their statement explained:
Alpha Centauri A actually didn’t look bad, but the outlook for mild axis dynamics on an exo-Earth modeled around star B was wretched. This may douse some hopes because Alpha Centauri AB is 4 light-years away, and a mission named Starshot with big-name backers plans to launch a space probe to examine the system, including for signs of advanced life.
So far, no actual exoplanets have yet been detected around either Alpha Centauri A or B. On the other hand, a planet is thought to orbit Proxima Centauri, a red dwarf star and technically our sun’s nearest neighbor (although no one knows for sure if Proxima is gravitationally bound to the A-B stars). This planet – called Proxima b – isn’t thought to be habitable, though. According to the new study’s principal investigator Billy Quarles, also of Georgia Tech:
We simulated what it would be like around other binaries with multiple variations of the stars’ masses, orbital qualities, and so on. The overall message was positive, but not for our nearest neighbor.
Read on. Interesting topic.
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