@Silveroak: You do have a point in that unless something happens to the entire solar system chances are relocation and resettlement could be done quite happily inside the oort cloud and for a fraction of the cost. And you're right. But there are celestial events which can and would render the entire solar system uninhabitable - gamma ray bursts & near earth supernovae are the most commonly cited. And that's before we get into the really bizarre posibilities of rogue stars or gravitational bodies ripping the solar system apart on a near miss/transit.
Thing is, humanity might get lucky and get the width and breadth of what's left of sol's main sequence. We might not. It's a nonzero chance - not a big nonzero chance, but a nonzero chance - and the kind of fundamental quetion that has to be, when you're talking about the survival of a species, is how low can that chance be and still be acceptable. What's an acceptable percentile on which to gamble everything we ever were and could be?
Granted, that's not going to be compelling logic to people who want returns on their investment now and frankly when it comes to long term planning we as a species kind of suck. But that's the math, if we care to look at it. There is a reason to make the attempt, even if it seems unnecesary now.
@Agricolus. I'm not so sure it would be in its death throes, honestly. A three day orbital period represents a fair chunk of kinetic energy and while the orbit is likely decaying it's likely doing so about on the same
|100K to millions of years. Not billions though, so in celestial terms pretty quickly |
as that of our moon, so as a piece of physical real-estate it should be around long enough even if it did take a 40,000 year mission. The big thing here though is that where there's one there are probably more - with the exoplanet detectiont echniques we have the other potential planets are just orders of magnitude harder to detect. Xavier Dumusque in one of these articles mentioned in the original post said that they could try and observe the signs of a planet in the habitable zone of the system, where it would have an orbital period of about 200 days, but it would take about a decade of continous observation of Alpha Centauri to have enough data as to hazard a substantive guess.