Exoplanet analysis is a growing field of scientific study as data pours in from the likes of NASA’s successful Kepler probe.
The abstract of a new paper explains its focus on this data:
‘Mean motion resonances and near-resonances up to the outer/inner orbital period ratio’s value of 5 and the denominator 4 are tested for all adjacent exoplanet orbits.’
Without delving into the nuts and bolts of the analysis here, let’s look at the list of results (click on image to view details):
By Marian C. Ghilea (2015)
The column ‘resonance type’ shows the planet:planet ratios we’re interested in.
Clearly there are many examples, although ‘near resonances’ are also included.
From the author’s concluding remarks:
‘Performing a simple analysis, the resonance or near-resonance states present in all the multiplanetary systems known to date can be found numerically using a computer analysis tool.’
‘The first results, presented in this paper, suggest different resonance or near-resonance distributions for different planet categories. The resonance/near resonance numbers of 2/1 and 3/2 appear to be dominant for the planets with larger masses while the 5/3 resonance seems to be the most common for terrestrial planets and mini neptunes. For giant planets, the 2/1 resonances are dominating at larger distances from the host star while the 3/2 resonance is more common at close distances from it. Resonances for values higher than 5/2 are encountered
only for planets with masses larger than 10 (ME*)’ [*Earth masses].
We can see from this that these ‘near resonances’ crop up regularly in exoplanet systems just as they do in our solar system e.g. Jupiter-Saturn 5:2, Neptune-Pluto 3:2.
Whatever the mechanism(s) involved, the frequency of their appearance can’t be regarded as accidental.
See also the Wikipedia page on orbital resonance