A new study by a team of astronomers from the United States and United Kingdom reveals that four Earth-sized planets have been discovered revolving around the nearby star Tau Ceti.
The four planets have masses as low as 1.7 Earth mass, and the two outer planets are located within the habitable zone, which means both could potentially support liquid water in their surfaces.
Since Tau Ceti is only 12 light-years away, the four planets are reportedly visible to the naked eye, even if they are some of the smallest planets ever found orbiting nearby sun-like stars.
Tau Ceti And The 4 Planets
As already mentioned, the four planets were found orbiting Tau Ceti, but the two inner planets were actually first detected and confirmed in 2013. However, the researchers say that their data seemed to show four rocky planets instead of just two, so they devised a way to make their technique more sensitive to weak planetary signals.
"We have introduced new methods to remove the noise in the data in order to reveal the weak planetary signals," University of Hertfordshire astronomer and lead author Fabo Feng said.
By making their technique more sensitive to these weak wobbles, the researchers found the third and fourth rocky planets orbiting Tau Ceti.
"We are slowly learning to tell the difference between wobbles caused by planets and those caused by stellar active surface. This enabled us to essentially verify the existence of the two outer, potentially habitable planets in the system," University of Hertfordshire astronomer and co-author Mikko Tuomi explained.
The two super Earth planets are located at a distance 0.5 and 1.25 times farther away from Tau Ceti as the Earth is to the sun. Since Tau Ceti is a little less intense than our solar system's own sun, both planets are considered within the habitable zone, and researchers believe both could potentially support a liquid surface, which could mean that they can support life, as well.
The only problem is that Tau Ceti is surrounded by a disc of space debris that makes it more susceptible to comet and asteroid impacts so, unless the outer planets are good at dodging, there is a lower probability for the outer planets to actually support life — or at least life as we know it.
Fine Tuning Planet Detection Techniques
According to the study, the four planets were detected by observing weak wobbles around the yellow dwarf Tau Ceti and by using sensitive techniques that can detect very small movements. In fact, the technique that was used attempted to detect movements as small as 30 centimeters per second.
The detection of the four planets is already a milestone, especially since it required techniques that can detect 30-cm-per-second movements but Feng said that the required limit to detect Earth-like planets is actually 10 cm per second.