If you are a "Star Trek" series lover, you will know what the popular Tau Ceti system is. Popularised in several fictional works, Tau Ceti is a very likely place to have life due to its proximity to Earth and the star's sun-like characteristics.
Since December 2012, Tau Ceti has become even more appealing, thanks to evidence of possibly five planets orbiting it, with two of these -- Tau Ceti e and f -- potentially residing in the habitable zone.
But now, applying a new approach that couples astronomy and geophysics, Arizona State University researchers report that, we can cross off our cosmic neighbour Tau Ceti from the list of hopefuls.
Using the chemical composition of Tau Ceti, the team modelled the star's evolution and calculated its habitable zone.
Although their data confirms that two planets (e and f) may be in the habitable zone, it does not mean life flourishes or even exists there.
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Planet e is in the habitable zone only if, we make very generous assumptions.
"Planet f initially looks more promising but modelling the evolution of the star makes it seem probable that it has only moved into the habitable zone recently as Tau Ceti has gotten more luminous over the course of its life," explained astrophysicist Michael Pagano, postdoctoral researcher and lead author of the paper.
Based upon the team's models, planet f has likely been in the habitable zone much less than one billion years.
This sounds like a long time but it took Earth's biosphere about two billion years to produce potentially detectable changes in its atmosphere.
A planet that entered the habitable zone only a few hundred million years ago may well be habitable and even inhabited, but not have detectable biosignatures.
Tau Ceti has been a popular destination for science fiction writers and everyone's imagination as somewhere there could possibly be life.
"But even though life around Tau Ceti may be unlikely, it should not be seen as a letdown, but should invigorate our minds to consider what exotic planets likely orbit the star, and the new and unusual planets that may exist in this vast universe," Pagano concluded.
The research appeared in the Astrophysical Journal.
