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Wednesday, December 19, 2012


Tau Ceti has Planets? maybe even an Earth-Like One in a Habitable Zone.

Location of Tau Ceti as seen from Australia at around 10 pm local daylight saving time, click to embiggen.

If you go out at around 10 pm tonight (or over the next week or so) and look north, you will see a unprepossessing star (magnitude 3.5) about 11 hand-spans up from the horizon. This is the star Tau Ceti.

A mere 12 light years away and a close twin of our sun, Tau Ceti has been the focus of many science fiction stories based on imagined planets.

But today it was announced that, like our neighbours Alpha Centauri and Epsilon Eridani, Tau Ceti may have real planets, Earth-like ones, with one possible world in Tau Ceti's habitable zone.

The Earth-likeness may be a bit strained, the planets have periods of 13.9, 35.4, 94, 168, and 640 days and minimum masses of 2.0, 3.1, 3.6, 4.3, and 6.6 M earth, respectively. It's the M earth 4.3 planet with a 168 day orbit which is in the habitable zone (that means its mass is 4.3 times that of Earth, it may be a  water world rather than a rocky world). I'll make a Celestia file after New Year.

Note the "may", which appears to have been dropped from many press releases. The planets have been uncovered by an international team of astronomers using clever statistical techniques on 14 years of observational data. the signals of these planets have been sifted from the years of noise. Their technique is a clever one, and has the potential to uncover more Earth-like systems, but requires independent confirmation before we get too excited.

The preprint of the paper is here.The PDF of the preprint is here (warning, big). ABC science online reporting here, Astrobiology Magazine article here. PhysOrg news article here.

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