Multiple resonances of exoplanets in the TOI-178 system

Credit: NASA

This six-planet system has orbit periods from 1.9~ to 20.7~ days, all much closer to their star than Mercury is to the Sun.

It was recently ‘upgraded’ from the three planets discovered in 2018 and 2019.

As usual, the key to understanding the timings of the orbits is to look at the conjunction periods of the neighbour pairs.


The planet names start with TOI-178 followed by a letter, so we’ll just refer to the letters here: b,c,d,e,f,g. Note that b is not in the main analysis, but is discussed at the end.

Working from the chart shown on the right, we find these conjunction alignments of planets c,d,e,f, and g:
9 c-d = 57.582932 days
3 d-e = 57.57645
2 e-f = 57.585146
1 f-g = 57.58892

Multiples of 3 and 2 are not unique in such systems, as shown by our analysis of the well-known Trappist-1.

Regarding planet b, the chart shows that all the other planets repeat their conjunction cycles in multiples of 41.
It appears that the b-c conjunctions occur in multiples of 42, although another interpretation might be possible.

Orbit summary
=============
1233 b = 2360.6487 days
729 c = 2360.8358
360 d = 2360.7698
237 e = 2360.9636
155 f = 2360.9491
114 g = 2360.8784

Data source: exoplanet.eu

via Tallbloke’s Talkshop

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January 2, 2021 at 04:45AM

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