Four Earth-sized planets found orbiting Sun-like star
Aug 10 2017 by Michele Stevens
This star supports a multi-planetary solar system that's been a point of focus for astronomers for some time, and now, an worldwide team of researchers led by the University of Hertfordshire in the United Kingdom have revealed something new about the system: it may include four Earth-sized planets, two of which could be habitable.
But, they did warn that a massive disc of debris around the star could be bombarding them with asteroids and comets, reducing their habitability. One of the new planets might have a mass as low as 1.7 Earths. That makes them the smallest worlds ever found around a star like our own sun, and has knock-on effects for the search for other planets like ours.
Modeling of large data sets from different observers made it possible for the team to differentiate between noise from stellar surface activity from small signals due to gravitational pulls from the Earth-sized planets orbiting the star.
A new study by an worldwide team of astronomers reveals that four Earth-sized planets orbit the nearest sun-like star, tau Ceti, which is about 12 light years away and visible to the naked eye.
Smaller planets require extra precision since the wobble is smaller and they can be harder to spot.
"We're getting tantalisingly close to observing the correct limits required for detecting Earth-like planets", said lead researcher Dr Fabo Feng, from the University of Hertfordshire.
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Dr Feng said: "Our detection of such weak wobbles is a milestone in the search for Earth analogues and the understanding of the Earth's habitability through comparison with these".
Tau Ceti is similar to our Sun in both size and brightness, and like our Sun hosts a multi-planet system.
Like the sun, it has a "habitable zone", a narrow region around it where conditions are favorable for Earth-like life.
Scientists believe the planets are located in an area that is not too hot or cold to support liquid water - a requirement for life. A habitable zone planet could have oceans, lakes and rivers.
The team, led by researchers at the University of Hertfordshire, discovered the "Super Earths" orbiting the Tau Ceti solar system right within the habitable corridor known as the "goldilocks zone". The Earth is situated halfway between the middle of the sun's habitable zone and its inner boundary. Their findings are to be published in the Astronomical Journal. This helped them eliminate two possible planets thought to exist based on signals received during research in 2013.
But even when using this technique the researchers found that there are definitely at least four rocky planets orbiting the star.
Mikko Tuomi, another researcher at the University of Herefordshire, explained, "We came up with an ingenious way of telling the difference between signals caused by planets and those caused by star's activity".