Scientists discover two potentially habitable 'super-Earth' planets

TRAPPIST 2.0? Scientists discover four Earth-sized planets orbiting Sun-like star

Brit astronomers are probing two new "super-Earth" planets in the hunt for life in our universe.

A new study by an worldwide team of astronomers, led by the University of Hertfordshire, reveals that tau Ceti, the nearest Sun-like star (about 12 light years away from the Sun), has four Earth-sized planets orbiting it - two of which could be habitable.

New advances in this technique, which is called Doppler spectroscopy (aka radial velocity or "the wobble method"), revealed the presence of four worlds tugging on Tau Ceti as they orbited it, detecting variations in the movement of the star as low as 30 cm/s (about 12 inches per second).

"We realized that we could see how a star's activity differed at different wavelengths, then used that information to separate this activity from signals of planets". Our detection of such weak wobbles is a milestone in the search for Earth analogs and the understanding of the Earth's habitability through comparison with these'.

The Herefordshire-Santa Cruz team previously collaborated on a study of Tau Ceti in 2013, a study that concluded that five much larger "super-Earth" planets orbited the star.

Download the News Nation Mobile App and stay connected with top stories from India and around the world. Every star has a habitable zone around it, with its size and location dependent upon the star's size and radiance. There is evidence of a vast debris disk that revolve around the star, increasing the chances of the planets being attacked by asteroids and comets. Two of these planets, the researchers say, might barely be on the edge of the habitable zone, that not-too-hot, not-too-cold region that can potentially support liquid water and even life.

"Together with colleagues in United Kingdom and US", Feng said "I have detected the smallest movement of a star caused by planets". Numerous other "potentially habitable" exoplanets discovered to date orbit dim red dwarf stars, which, for a variety of reasons, could prove hostile to life.

"We are getting tantalizingly close to the 10 cm per second limit required for detecting Earth analogs", said team member Dr. Fabo Feng, also from the University of Hertfordshire. The earth located halfway between the middle of the zone, fit for life, and her domestic turn.

In this case, the team obtained observations from the HARPS spectrograph on the European Southern Observatory in Chile, and Keck HIRES (above) on the W.M. Keck Observatory in Mauna Kea, Hawaii. The results are published in a study in the Astrophysical Journal.

The four Earth-like planets are the smallest orbiting around tau Ceti.

"Since then we've painstakingly improved the sensitivity of our techniques and could rule out two of the signals our team identified in 2013 as planets".

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".

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