Tau Ceti has an enduring whiff of the Sixties about it. Peace, love, dolphins. The connotations are not a fluke: Tau Ceti was lifted out of back-of-the-Greek-alphabet obscurity in 1960, when it and Epsilon Eridani shared the distinction of being the target stars for the Project Ozma SETI experiment.
Yes, that was years before the Summer of Love, but - especially in that pre-Internet era - it took time for ideas to filter into the science fiction popular culture. Before Project Ozma, I doubt that many people had heard of Tau Ceti.
It got the attention of Project Ozma's designers because it is close to Sol (11.9 light years) and similar in spectral type (G8.5). Alpha Centauri is closer and more similar, but the prevailing view at the time was that double (and other multiple) stars went poorly with planets. Indeed this remained a cause for hesitation right up until planets were found in multiple-star systems, recently including Alpha Centauri itself.
And now planets - five of them - have (possibly) turned up around Tau Ceti as well. They have minimum masses between 2 and 6.6 times Earth mass, and orbit between 0.11 and 1.35 AU from the parent star.
Tau Ceti radiates at just over half (0.52) solar luminosity. Thus the fourth planet (at 0.52 AU) and fifth planet orbit respectively at the thermal-balance equivalent of 0.76AU and 1.87 AU from Sol.
A bit farther out than Venus, and considerably farther out than Mars. Neither sounds like Paradise World, but depending on a host of secondary assumptions they might both be in the habitable zone.
Minimum masses are 4.4 and 6.3 Earths, which for the inner planet is all too suggestive of a super Venus. The outer planet could be more promising, and if it has a deep hydrosphere the surface gravity could even be comparable to Earth's.
Proviso time: Sky & Telescope throws some cold water on the whole planetary system. The detection method is experimental, and the indications suggesting planets are no louder than the noise in the data. This does not rule out valid detection, but makes it the equivalent of eavesdropping on an interesting conversation at a loud party.
In this case my gut feeling is that S&T is being a bit too cautious - that the Tau Ceti planets will likely turn out to be real. And along with the Alpha Centauri finding, it seems as though extrasolar planets, including kinda sorta Earthlike ones, are - so to speak - creeping closer to Sol.
Reaching Tau Ceti with any semi-demi-plausible drive is outrageously difficult. Refer to the Alpha Centauri post and comment thread for speculation. But it is perhaps time to assess just where we stand when it comes to planets and life.
According to the Extrasolar Planets Encyclopedia, there are now 854 known, that is to say confirmed, extrasolar planets. (The Tau Ceti system is not listed in their main catalog.) Extrasolar worlds thus outnumber 'major' Solar System planets by a hundred to one, an impressive balance.
Planets are common. Planetary systems are odd. So far as I can tell, we have not yet found any systems that look a lot like ours - rocky inner planets, larger gas or ice-rich outer ones, most or all in near-circular orbits. This may be a mere selection effect.
And in spite of the Kepler findings we have not yet found an 'Earth' - a planet of similar size orbiting at a distance closely equivalent to 1 AU. This could be a different sort of selection effect. We are finding a decent number of kinda-sorta Earths, and hitting bingo depends on the constraints you set.
As for the biological implications? Alas, we still have a data set of precisely one. Which means that we don't really have a clue as to how common life is, or what conditions are needed for it to appear.
Project Ozma, like rocketpunk-era SF, lay in the bright glow of the Miller-Urey experiment in 1952. This experiment showed that, given an atmosphere similar to what was then thought to be Earth's primordial atmosphere, the simpler molecular building blocks of light were easy to produce. Life in a test tube seemed just around the corner.
As with controlled fusion and human-like AI, things have not worked out that way. On the other hand, I don't get the impression that biochemists have made a major research project out of trying to brew up living organisms. The project has no obvious application except to generate media hysteria, not good for funding proposals.
Behind all discussions of life lurks the Fermi Paradox. Yes, it is specific to intelligent (or at least interstellar-signaling) life, not life in general. But the more common life is elsewhere in the universe, the more opportunities it has to make its presence known. And the harder to explain why it hasn't.
The image of dolphins comes from this Flickr page. Back around the 1970s, National Lampoon magazine included dolphins (meaning dolphin intelligence) in a list of Great Disappointments. True? False? Irrelevant?