Tau Ceti: The next Earth? Probably not

Wednesday, May 27, 2015
by Nikki Cassis

Tau Ceti is a star that's close to Earth. It also a little bit like our star, The Sun. Tau Ceti has often been seen as a place where extra-terrestrial life might be found. The science fiction series Star Trek portrayed Tau Ceti as an alien home world. It also shows up in the Halo: First Strike novel.

The star has become even more popular since December 2012. That’s when scientists found possible evidence of five planets orbiting Tau Ceti. Tau Ceti e and Tau Ceti f were two of those planets. Scientists think life might be able to evolve on e and f. Regions like this are called “habitable zones.”

Researchers from Arizona State University study Tau Ceti e and f. They wanted to know if e and f really were in habitable zones.

“Planet e is in the habitable zone only if we make very generous assumptions,” says ASU researcher Michael Pagano. At first, planet f looked more promising to be habitable. But Pagano says that computer models of the evolution of the star show it has only moved into the habitable zone recently. And Tau Ceti has gotten more luminous over the course of its life, says Pagano. He is an astrophysicist who led the research team.

The team found that planet f has likely been in the habitable zone less than 1 billion years. “Less than 1 billion” still sounds like a long time for humans. But it is a very short time for stars and planets. It took about 2 billion years for the Earth’s atmosphere to change enough that scientists could detect signs of life. Scientists might not be able to detect these signs on a planet that has been in the habitable zone for only a few hundred million years. So even if Tau Ceti f could support life, scientists might not be able to find signs of it.

Pagano says his team didn’t pick Tau Ceti “hoping, wanting or thinking” it would have life. They picked it because they thought the planets around the star might be “alien” new worlds. In other words, Tau Ceti e and f might have life that’s very different from life on Earth.  

Planets e and f might have very different life, or none at all. That’s because the star Tau Ceti is made differently from our star, The Sun. Tau Ceti has different minerals in it. These minerals could make the planets orbiting Tau Ceti have different environments from our Earth.

The researchers think that Tau Ceti’s planets might have different amounts of volcanic and tectonic activity. Volcanic activity is how volcanoes behave. A planet with a lot of volcanic activity has a lot of volcanoes that can explode or emit lava. Tectonic activity is one of the causes of volcanic activity. It is how the surface of a planet moves or changes. Earthquakes are another example of tectonic activity.

Volcanoes and tectonic activity have a big impact on the Earth’s ability to support life, or its habitability. Scientists believe they could also have a big impact on life on other planets like Tau Ceti f.

Tau Ceti has been a popular destination for science-fiction writers, Pagano says. In everyone's imagination, it could possibly have life. But life around Tau Ceti may be unlikely. However, it should not be seen as a letdown. It should inspire our minds to consider what exotic planets likely orbit the star, Pagano says. There are new and unusual planets that may exist in this vast universe.

This work was supported by funding from the NASA Astrobiology Institute and NASA Nexus for Exoplanet System Science. The results of the research are appearing in a paper published in the Astrophysical Journal. The team also included ASU astrophysicists Patrick Young and Amanda Truitt. Mineral physicist Sang-Heon (Dan) Shim was another team member.