The Next Earth? Tau Ceti May Not be as Hospitable to Life as Previously Thought

The hunt for alien life continues, but one planet may not be as hospitable to life as scientists once believed. Researchers have examined our cosmic neighbor, Tau Ceti, and have found that the system is unlikely to host life.

The Tau Ceti system, which has been popularized in several fictional works, has long been thought of as a likely place to have life due to its proximity to Earth and the star's sun-like characteristics. In 2012, this system became more appealing when scientists discovered that there were five planets orbiting the star. Two of these planets actually resided in the habitable zone.

Now, though, it seems as if these hopes for life are dashed. Using the chemical composition of Tau Ceti, the researchers modeled the star's evolution and calculated its habitable zone. Although their data confirms that planets e and f may be in the habitable zone, this doesn't mean that life flourishes there.

"Planet e is in the habitable zone only if we make very generous assumptions," said Michael Pagano, lead author of the new paper, in a news release. "Planet f initially looks more promising, but modeling 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."

Based on the new models, planet f has probably been in the habitable zone for less than 1 billion years. To make a comparison, Earth's biosphere took about 2 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 be habitable, but not have any 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 the vast universe,"' said Pagano.

The findings are published in The Astrophysical Journal.

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