Centauri A and B continue to stand out as likely venues for terrestrial planets. What a change since the days when it was thought orbits in binary systems like this one would be completely unstable. Today we believe that both the major Centauri stars could support small, rocky worlds within about 4 AU, and that such planets are as likely, if not more so, to form there as around our own Sun. The latter insight emerges directly from the work of Elisa Quintana and Jack Lissauer.
Add to that two other factors: At UC-Santa Cruz, Greg Laughlin and Jeremy Wertheimer have shown that Proxima Centauri could perturb the debris disk surrounding the Centauri stars enough to deliver volatiles to inner worlds there. Laughlin has been arguing the Centauri case for some time now, discussing not just the Proxima factor but pointing as well to the metallicity of Alpha Centauri, which is high enough to provide the kind of materials needed to form planets analogous to Earth.
Keen on detecting such a planet, Laughlin now advocates a radial-velocity investigation of Centauri B, toward which end he has been working up detailed feasibility studies. The method: model terrestrial planetary systems in stable orbits using accepted accretion models, then work out hypothetical observing strategies. The radial velocity measurements thus produced are fed to the downloadable systemic console for manipulation.
So far, so good. In fact, working with this data at the highest time resolution produces clearly readable planetary signatures. “The peak at 351 days corresponds to an Earth-mass planet,” Laughlin writes. “The three neighboring peaks correspond to smaller planets having masses on the order of Mars.”
Remember, these planets are simply simulations. But detecting Earth-like worlds in Centauri space looks to be a workable proposition provided we have time and resources to make the needed observations (Laughlin worked with 96,464 radial velocities obtained in a simulated five-year observing run). And there are numerous complications, not the least of which involve the proximity of Centauri A. Can a special purpose telescope be built to handle these observations, given that existing instruments aren’t going to let themselves be comandeered for the length of time required? Laughlin promises more on system modeling and telescope strategy soon.
This is excellent news. I realize it is a simulation but still quite exciting. An earth-sized planet and three Mars-sized ones that close ought to fire up the imagination and stimulate our wonderment.
I am not a believer in SETI (oh, how I hope I am wrong). To run before my horse to market if the planets do exist and there is no intelligent life in the system than the answer to Drake’s equation looks an awful lot like zero.
Whatever the astronmers find planets or not it is great that people keep exploring and searching even in those places where we already “know” the answer.
A few weeks back, in April, planet hunters had announced the discovery of a 1.5 Earth sized planet around the red dwarf star Gleise 581 using the common radial velocity method; the planet was located within the habitable zone of the star and was speculated to being a rocky terrestrial world like Earth. I know that red dwarfs are faint, and so the radial velocity method is much easier to use on them than brighter stars like Alph Centauri, but because Gleise 581’s distance from Earth is so great, (about 20 light years), shouldn’t it be that this method would work just as well, if not better, on the Alpha Centauri system? If so, then has there ever been any reported usage and/or results on the usage of this method on the Alpha Centauri system?
P.S.- I have always been a strong advocate for possible habitable planets in all members of the Centauri system.
Justin, your question about radial velocity and the Centauri stars is a good one. One difference other than the size of the stars involved is the fact that we’re dealing with a triple system at Alpha Centauri. However, radial velocity measurements could indeed be used there. One problem is the sheer length of the observing run that an instrument like HARPS would have to make to get the needed data. I’m no expert on this, but Greg Laughlin is, and I recommend you check out his systemic site via the links in the story above. Have a look, too, at these thoughts on Proxima:
You’ll see that there is reason for optimism about the existence of rocky worlds in this system. But at this point we still don’t know for sure. You’ll also, be interested, in Elisa Quintana and Jack Lissauer’s work on close binaries. Here’s one link that may be useful background: