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A planet around Tau Ceti with an Earth-like moon

Tau Ceti is surrounded by a dust disk, which is as extensive as the Kuiper Belt in the Solar System, but ten times as massive [1]. It is not yet settled if the dust disk has once been more massive in the past or if it has grown as a result of interaction with planets.

Five planets are known to orbit Tau Ceti, named Tau Ceti b to f. Planets e and f are near the inner or outer edge of the star's habitable zone, respectively [2].

However, a recent study has demonstrated that Tau Ceti's chemical compositions differs in many important points from the Sun [3]. Magnesium is 70% more common than silicium. This means, an earthlike planet around Tau Ceti would have a mantle dominated by magnesium rather than silicium, as on Earth. Magnesium compounds often melt at higher temperatures than silicium compounds, resulting in a less viscous planetary mantle layer. This would have drastic effects on the flow of the molten mantle and movement of tectonic plates. Planets around Tau Ceti may thus be less likely to be life-friendly than Earth.


1. GREAVES, J. S., et al. The debris disc around τ Ceti: a massive analogue to the Kuiper Belt. Monthly Notices of the Royal Astronomical Society, 2004, 351. Jg., Nr. 3, S. L54-L58.

2. TUOMI, Mikko, et al. Signals embedded in the radial velocity noise-Periodic variations in the τ Ceti velocities. Astronomy & Astrophysics, 2013, 551. Jg., S. A79.

3. PAGANO, Michael, et al. The chemical composition of τ Ceti and possible effects on terrestrial planets. The Astrophysical Journal, 2015, 803. Jg., Nr. 2, S. 90.

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