YZ Ceti update: resonant echoes of Pluto’s moons

Posted: February 9, 2020 by oldbrew in Astrophysics, Fibonacci
Tags: , ,


There’s been a data update for the three planet system of star YZ Ceti, which featured in our 2018 post: Why Phi? – resonant exoplanets of star YZ Ceti. According to NASA the third planet YZ Ceti d is a ‘super Earth’, about 1.14 times the mass of our planet.

The paper:
‘The CARMENES search for exoplanets around M dwarfs.
Characterization of the nearby ultra-compact multiplanetary system YZ Ceti’
(Submitted on 5 Feb 2020)

With an additional 229 radial velocity measurements obtained since the discovery publication, we reanalyze the YZ Ceti system and resolve the alias issues.

The re-calculated synodic periods for planets b,c,d are:
b-c 5.9514156 days
c-d 8.9250255

3 b-c = 17.854246
2 c-d = 17.8650051
This is a first-order (3:2) resonance.

Orbit periods:
53 b = 107.10611 days
35 c = 107.09615
23 d = 107.09398
(Data: exoplanet.eu)

18 b-c (53-35) = 12 c-d (35-23) = 30 b-d (53-23)
Dividing by 6, the synodic ratios in ascending order are:
2 c-d = 3 b-c = 5 b-d (2:3:5)
2,3, and 5 are Fibonacci numbers.

The same ratios apply to three of Pluto’s moons. Quoting our post Why Phi? – Moons of Pluto:
‘The ratios of synodic periods are such that there are 5 Styx–Hydra conjunctions and 3 Nix–Hydra conjunctions for every 2 conjunctions of Styx and Nix.’

That line comes straight from Wikipedia.

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