There are billions and billions of stars in the universe, each unique and special. But few have captured the imagination of scientists as Tau Ceti, a yellow dwarf star nestled in the constellation Cetus, just a mere 11.9 light-years away from us.
Tau-Ceti: Sun-like in more than one way
The Tau Ceti system seems to be a favorite of science fiction shows (especially Star Trek). We haven't been able to locate those types of humanoid lifeforms anywhere in the universe yet, but the Tau Ceti system seems like it could be as good a neighbor as anywhere to harbor at least some type of life.
Tau Ceti is a G-type main-sequence star, much like our own sun, and is believed to be around nine billion years old. For comparison, our Sun is just over 4.5 billion. It is the nearest single G-type star to us, and its relative proximity makes it an ideal target for study. Indeed, Tau Ceti has been researched extensively over the years, with astronomers keen to learn more about this fascinating system.
Perhaps the most intriguing feature of Tau Ceti is its large debris disk, comprised of rock and ice left over from the formation of the star and its planets. This debris disk is a sure sign that planets may be present, and astronomers have indeed detected at least four potentially habitable planets in the system, with more waiting to be discovered.
The first two planets were discovered in 2012, and they were found to be about 4.3 and 6.6 times the mass of Earth, respectively. These planets orbit very close to the star, with orbital periods of just 13.9 and 35.4 days.
More recently, in 2017, two more planets were discovered around Tau Ceti. These planets are about 1.7 and 1.8 times the mass of Earth, and they orbit at distances of 0.55 and 0.75 astronomical units (AU) from the star, respectively. An AU is the average distance between the Earth and the Sun, which is about 93 million miles.
The planets were detected by observing how Tau Ceti moved and wobbled. To do so, the researchers needed techniques to pick up changes in the star's movement as small as 30 centimeters per second.
The discovery of these four planets has made Tau Ceti a prime candidate for the search for life beyond our Solar System. The two inner planets are likely too hot to support life, but the two outer planets are located in the system's habitable zone, where temperatures are just right for liquid water to exist on their surfaces. Liquid water is a key ingredient for life as we know it, and its presence on a planet is one of the main criteria for habitability.
However, it is important to note that the discovery of planets around Tau Ceti does not necessarily mean that they are habitable or that they harbor life. Many factors go into making a planet habitable, such as the presence of an atmosphere, the composition of the planet's surface, and the amount of radiation and stellar activity from the star. Obviously, more research and observations will be needed to determine the potential habitability of these planets.Something like Project RIGEL, for instance.
Searching for alien life on Tau-Ceti
The project is an ambitious plan to transport a "robot geologist" to a distant world orbiting a star similar to our Sun.
Nonetheless, there is a minor issue. Current space travel technology would require at least a thousand years to reach even neighboring Tau Ceti.
Even so, that didn't stop Philip Horzempa, a planetary scientist at LeMoyne College in Syracuse, New York, from publishing a 2021 white paper last fall outlining the specifics of Project RIGEL (Robotic Interstellar GEologicaL probe), an ambitious multi-generational mission.
Project RIGEL, which aims to land on and explore the surface of an exoplanet, will be difficult. However, the paper makes it clear that the mission should be put together as soon as possible because of the enormous engineering challenge it presents. The article claims, "For the first time in history, an explorer from Earth will be able to walk about the surface of an alien planet," albeit a machine, a "geologist avatar" stand-in for humanity.
“This is a mission that will span centuries,” writes Horzempa. “It does not assume undefined breakthroughs that would allow rapid transit across interstellar space. The RIGEL concept exists within the known laws of physics. We can send a robot proxy to a distant exoplanet, but patience is required. The daunting chasm between stars dictates the major features of the Rigel craft. It must be built to last for centuries and it must act completely on its own.”
A Tau Ceti system planet is the intended destination. It's probably the nearest system with a temperate rocky planet like Earth or Mars, but more study is needed to confirm this. The difficulty lies in engineering a spacecraft that can travel at speeds far beyond what is currently achievable.
The scientist suggests that engineers shoot for a speed of 2,000 miles (3,200 kilometers) per second, or just over one percent of the speed of light. Tau Ceti may be relatively close to Earth, but it is still almost 12 light-years away. This means that even if we just send signals or messages to the star, it will take over a decade to reach their destination, and any response will take just as long to reach us, so anyone involved in such a project should be ready for the long haul.
"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," says astrophysicist Michael Pagano, Arizona State University postdoctoral researcher and lead author of a 2015 paper appearing in The Astrophysical Journal studying Tau Ceti.
Sun-like stars are believed to be the best targets for the search for habitable Earth-like planets. In contrast to more common dwarf stars, such as Proxima Centauri and Trappist-1, they are not so faint that planets would be tidally locked, always presenting the same side to the star.
Tau Ceti is comparable to the sun in terms of size and luminosity, and both stars contain multiple-planet systems. Tau Ceti could be the best option out there in our search for possible habitation and Earth-like planets.