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4 Earth-Sized Planets Discovered Around Nearest Sun-Like Star

S u m m a r y :
Four Earth-sized planets have been discovered around the nearest sun-like star. The system is located 12 light years away from us, which makes it easily visible to us. The findings are published in the Astronomical Journal.

4 Planets Around tau Ceti

The nearest sun-like star, tau Ceti, situated around 12 light years away from us, has four planets comparable to our Earth in size orbiting it, says an international team of researchers.

Tau Ceti resembles our sun in terms of both size and brightness and the hosting of several planets.

Wobbles Reveal Planetary System

The discovery of the system of planets was made through the study of tiny wobbles in tau Ceti’s movement whose subtle differences as low as 30 centimeters per second were detected. The finding is huge in the world of science because sun-like stars are associated with better chances of habitable worlds.

“We are now finally crossing a threshold where, through very sophisticated modeling of large combined data sets from multiple independent observers, we can disentangle the noise due to stellar surface activity from the very tiny signals generated by the gravitational tugs from Earth-sized orbiting planets,” says one of the study authors, Steven Vogt, from UC Santa Cruz.

This minimum might go to 10-centimeter-per-second, says lead author Fabo Feng from UK’s University of Hertfordshire; this would allow the researchers to detect Earth analogs. Feng explains that identifying these weak wobbles is an important step in the search of Earth-size planets.

Habitable Worlds?

To better appreciate the relatively short distance between tau Ceti and us, consider this: we can see the star with the naked eye. Its planets, with masses at around 1.7 Earths, are the smallest ones to be orbiting a sun-like star that is in close proximity to us. Furthermore, two of these are super-Earths, the outermost ones, are found in the habitable zone, an area around a star where it is believed that liquid water might exist on the surface of heavenly bodies.

The outer pair of planets are possible candidates for habitability in spite of being vulnerable to collisions from asteroids and comets from the huge disk of debris that surrounds their star.

The team of astronomers had to differentiate between data pertaining to signals coming from the planets and that relating to activity of the star. They, thus, had to improve their techniques to cater for a greater sensitivity.

“But no matter how we look at the star, there seem to be at least four rocky planets orbiting it,” says study author Mikko Tuomi from the University of Hertfordshire. “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.”


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