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Hey neighbors! Nearest sun-like star hosts 4 Earth-sized planets
10 August 2017, 01:08 | Justin Tyler
The discovery was made by an international group of astronomers
According to lead author Fabo Feng of the University of Hertfordshire, UK, the researchers are getting tantalizingly close to the 10-centimeter-per-second limit required for detecting Earth analogs. Two of those planets, tau Ceti g and h, are newly described, whereas tau Ceti e and f are the same ones described previously, but now with lower mass estimates (a minimum mass of 3.9 Earths for each).
An global team of scientists devised a new, more accurate and sensitive method of detecting planets by looking for "wobbles" in the star's movement caused by the minute gravitational tug of orbiting planets, while also better ruling out false positives coming from activity on the star itself.
These planets are detected by observing the wobbles in the movement of tau Ceti. The technique, they claim, is now almost precise enough to detect Earth-mass planets.
Dr Tuomi continued, 'We're slowly learning to tell the difference between wobbles caused by planets and those caused by stellar active surface.
"This enabled us to verify the existence of the two outer, potentially habitable, planets in the system".
Neither of Tau Ceti's "super-Earths" lie in the centre of its habitable zone.
If so, that means they're far less likely to be habitable - and there's also the issue of the super Earths hanging uncomfortably close to the outskirts of Tau Ceti's habitable zone - although it's premature to abandon all hope. The gravitational tug of nearby planets causes the parent star to wobble around the shared center of mass, and the resulting doppler shift in the starlight can be measured. Numerous other "potentially habitable" exoplanets discovered to date orbit dim red dwarf stars, which, for a variety of reasons, could prove hostile to life. Space.com noted that a large debris disk much like our own Kuiper Belt surrounds Tau Ceti, which in the absence of a large Jupiter-like planet to absorb projectiles, may be constantly bombarding its planets with comets and meteors.
"The planets in the habitable zone around nearby dwarf stars, like Proxima Centauri or TRAPPIST-1, are exposed to strong stellar winds that could strip their atmospheres", Loeb said.
Tau Ceti is located just 12 light-years away from you and me, and it's nearness and brightness has long made it a mainstay in sci-fi and video games - but now it looks like the star's potential to support alien life may not just be the stuff of fantasy.
The four planets are the closest Earth-like worlds yet discovered.
"The most important discovery in this work is that we have detected the weakest signal and are reaching the limit of detecting Earth analogs using radial velocity method", Feng said.
In the search for potentially habitable Earth-like exoplanets, those found orbiting Sun-like stars are good candidates.
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