The 100YSS mission currently includes a discussion about Alpha Centauri (our closest star) as a potential target destination, but is it really the best candidate for the 100YSS?

To narrow the question's scope, I'll add that my own criteria in asking the question make the discovery of extraterrestrial life the highest priority, so I would add:

  1. stars with larger numbers of Earth-like planets are better than stars with fewer (in hopes of maximizing the probability of finding life)
  2. closer stars are better than farther stars (to minimize travel time)
  3. stars with more stable surroundings (like our star) are better than stars with less stable surroundings (like stars in a binary system such as HDE 226868/Cygnus X-1)
  • $\begingroup$ Since inhabitable worlds do not necessarily imply inhabited worlds, it would probably be more worth our while to choose a star system that had other interests besides just extraterrestrial life. That is, unless we could somehow guarantee that the star system we chose almost certainly has life of some kind (such as through analysis of planetary atmopsheres, etc.). $\endgroup$
    – called2voyage
    Jul 24, 2013 at 18:30
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    $\begingroup$ I think "Best candidate" may have set off the subjective question alarm. I would suggest you rephrase your question to: "How can we determine the optimal destination for a manned mission beyond our solar system?" $\endgroup$
    – JohnB
    Jul 24, 2013 at 18:58
  • $\begingroup$ CopyrightX, not everybody understands the scope of the 100YSS mission. The synopsis can be found only through the Web Archive, for instance: web.archive.org/web/20120522192408/http://www.100yss.org/pdf/… $\endgroup$ Jul 24, 2013 at 19:25
  • $\begingroup$ Please note that there is scarcely a word about sending humans into an interstellar voyage at 100yss' web site. Maybe I'm not looking at the right places... $\endgroup$ Jul 24, 2013 at 19:32
  • $\begingroup$ @DeerHunter see "multigenerational spacefarers" $\endgroup$ Jul 24, 2013 at 19:34

1 Answer 1


Through unmanned missions.

A set of probes of moderate complexity would be able to gather enough data to help making the decision.

I can imagine prerequisites of such probes.

  • as it gains speed, it discards trailing segments. Possibly another probe just with such segments is sent. At preprogrammed time the segments activate and start acting as radio relays - we don't need the probe back, just its data, so the "way back home" of the data would be at speed of light, from relay to relay.

  • The probe contains a central module with a good spectrometric telescope to provide automated survey of the planets, and a couple landers similar to simple Mars landers, autonomous vehicles capable of airbraking and landing on potentially inhabitable planets. We don't need inhabited, just inhabitable by humans or at least resources-rich so that the actual 100YSS could establish a base of operations.

  • The core module picks promising candidate planets using the telescope data, and deploys the landers to these. The probes relay their findings to the core module, the core module sends it back home through the relay system.

  • One such probe is sent to each candidate star system.

  • As the probes are underway, we use the time to develop actual spaceship, develop needed technologies for easily deployable sustainable base, and so on. We should have it ready once the replies start coming in, then we pick the best candidate planet using the gathered data - if there is any life in given system, a most human-habitable planet in that system. If there is no life in any of them, most human-habitable of them all.

  • $\begingroup$ I dunno. I think a decision could be made with data we already have. True, it won't be as well-informed a decision as one you describe here, but it would certainly be much timelier. $\endgroup$ Aug 1, 2013 at 1:07
  • $\begingroup$ @CopyrightX: I expect at least 50 years gap between capability to build unmanned probe and a manned vehicle; why not use that time well and send these probes early? $\endgroup$
    – SF.
    Aug 1, 2013 at 6:58
  • $\begingroup$ Perhaps you're right, but I think we could build something like a Bernal Sphere today if we decided to spend the money on it. I don't think there is a material science or engineering hurdle in such a project that we could not clear right now. Gerard O'Neill thought the same in the 1970s after very careful analysis (which I've not done myself), so I'm hard pressed to believe that 40 years later we'd face insurmountable problems with that project. What specific technology for interstellar travel do you suppose we'd need 50 years to build before beginning to accelerate such a Bernal Sphere? $\endgroup$ Aug 1, 2013 at 17:49
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    $\begingroup$ @CopyrightX: Build - possibly. Propel so that it gets there within, say, 10 generations - not really. We have some quite good projects of space habitats. We don't have the resources to bring hardware needed to build them over the orbit. This is not something of order of magnitude of "NASA budget over the cold war". It's the order of magnitude "all of humanity contributes 20% of their income". $\endgroup$
    – SF.
    Aug 1, 2013 at 19:27
  • $\begingroup$ +1 for answering a question marked as "manned-flight" with probes. $\endgroup$
    – mart
    Nov 4, 2013 at 15:05

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