Question

Could the Alpha Centauri system support earth-like planets?

Yes. The Alpha Centauri star system, which consists of 3 stars (Alpha, Beta, and the distant Proxima) is the nearest good candidate for life. Both Alpha (1.5 sun luminosity) and Beta (0.44 sun luminosity) are fairly large stars very similar to our own sun. Because they are the right size, their habitable zones--the boundaries that define the conditions essential to life--are expansive enough to provide a viable heat source and allow for earth-like planets to exist.

Because the Alpha Centauri system is not a single star, there are some complications. For years, astronomers worried that the gravitational attractions of multiple star systems would prevent planets from forming or destabilize their orbits. However, present views point to some unusual alternatives. One such situation is if the planets’ orbits are sufficiently close to one of these two stars. In this case, planetary orbits might be stable enough to keep the Alpha Centauri system in gravitational balance. Another possibility may be that planets could orbit at a large distance from both members of the double-star system, such as along the orbit of Proxima Centauri. Unfortunately, revolution at 50,000 times the Earth-Sun distance from the star cluster's center of mass is not very promising. Why? Organisms would have no light to live by brighter than the Moon. Even if these Earth-like planets revolved around Proxima itself, they would require an extremely small orbit because of the dim star's tiny habitable zone. Nevertheless, the Alpha Centauri system remains one of our best candidates for life. For general information about this star system, see click here.
October 29, 2001