Despite all the exotic exoplanetary systems discovered so far, the one potential system that has the power to truly galvanize astronomers as well as the public is Alpha Centauri A and B.
The star system lies a mere 4.3 light years away, but unfortunately it is only clearly visible from southern skies. The third member of the system, a red dwarf star called Proxima Centauri, yields no evidence for planets and is so far from the binary pair as to be inconsequential.
No planets have yet been discovered orbiting A and B either, but given the preponderance of planets everywhere else we look in our galaxy, it would be a much bigger shock if planets weren't found in the Centauri system after detailed surveys.
ANALYSIS: Do Aliens Go Invisible by 'Going Green'?
The stars are prime targets because they are similar to our sun in terms of age and temperature. There has been plenty of time for Darwinian evolution to yield an extraterrestrial Serengeti of creatures on any planets lying in the habitable zones around either star.
Several models have shown that both stars, separated by as far as two billion miles, are capable of forming terrestrial planets despite the perturbing influence of their binary companion. In fact, having a companion star can be a gravitationally stabilizing influence, like massive Jupiter is in our solar system.
Duncan Forgan of the Scottish Universities Physics Alliance at the University of Edinburgh and colleagues, have taken a closer look at habitability around the cooler and less active member of the pair, Alpha Centauri B. That star has a wide habitable zone stretching the equivalent of the distance from just inside the radius of Venus' orbit to the nearly the radius of Earth's orbit.
Forgan’s study take into account the fact the Alpha Centauri A would also heat a planet in Alpha Centauri B's habitable zone. Alpha Centauri A is in an elliptical orbit around Alpha Centauri B. This means that when it comes closest to B's habitable zone the star would quickly appear to grow three times brighter than when farthest away. This mean a frozen Mars-like planet on the edge of the habitable zone might be periodically thawed out.
NEWS: Weird Exoplanet Discovered Orbiting Two Stars
An ocean planet like Earth inside the habitable zone would have more thermal inertial to maintain a steady temperature despite the warming effect of Alpha Centauri A's close approach. But arid planets would experience a wider temperature swing. In any event the warming would be brief but intense, raising planet-wide temperature by a few degrees.
This would happen every 70 years, which is the period of A's orbit. Sleep specialist Michael Breus' research implies that life on such a planet might develop two circadian rhythms corresponding to both the length of day on the planet, and Alpha Centauri A's orbital period. This would alter the available habitable areas on the planet's surface by a few percent, say the researchers.
NEWS: What's Taking E.T. So Long to Find Us?
Given the awesome power of biological evolution, it's likely life would easily evolve to cope with living with a second star. There may be planet-wide migrations with anticipation of the approaching "super-summer." And there would be a variety of other novel coping mechanisms.
Intelligent life on such a planet would note Alpha Centuri B's passage in front of the A star every 70 years. This might be a culturally profound event leading to a Times Square-like News Year's celebration. Or, maybe it would be a period of fear and atonement, depending on the culture's level of science literacy.
If the aliens think like us, no doubt they would have soothsayers predicting the "End of Times" with the approaching transit. Pseudoscience books would be a big business and perennial for the Beta Centaurians. Come to think of it, such books are in our culture despite the fact we don't have such interplanetary melodrama.
Image credits: NASA, ESO
No comments:
Post a Comment