A Natural History of Enkei

Enkei is a double planet and the second planet to orbit Magnus along with its sibling planet, Yaima. Enkei and Yaima are hypothesised to have formed from a single large planet approximately 5 billion years ago. The theoretical "proto-planet" would have been struck by a smaller planetary body, splitting the proto planet into two seperate bodies. This impact is believed to be the reason why Enkei's iron core is smaller than what would be expected for its size while Yaima's iron core is relatively larger.

 

It has been speculated that when Enkei and Yaima formed, they were close enough to exchange atmospheres. During this period it is possible that early life forms may have migrated from one planet to another although this does not align with the currently accepted timeline for the origin of life. The earliest known fossil stromatolites indicate that bacteria has existed for at least 4 billion years. Since deep-sea hydrothermal vents exist on both Enkei and Yaima, it is entirely possible that life arose independantly on both planets. This does not rule out the possibility of cross-planet species migration.

Enkei's day lasts 32 hours, being slowed over time by Yaima, which is tidally locked to Enkei. Enkei has a shallow axial tilt of 12.8°. Due to the low obliquity seasons are not very pronounced throughout most of the planet. The southmost continent, Polaris, exhibits the most seasonal variation. Much of Polaris can spend up to six months in near-total darkness. The greenhouse effect, axial tilt and arangement of continents mean that the majority of landmasses only experience two seasons - wet and dry.

The unique orbital mechanics between Enkei, Magnus and Ignis result in Enkei's eccentricity fluctuating on an anual basis. This change in eccentricity typically means that Enkei's climate alternates between low seasonal variation and moderate seasonal variation. A year with mild seasons is typically followed by a year with more pronounced seasons. This also effects Enkei's semimajor axis which can vary by up to 0.03AU over a span of around 8 years. The change in insolation results in extreme summer and winter periods, each lasting around 4 years. The intensity of these periods are difficult to predict but are usually significant enough for extensive ice sheets to form and thaw on Polaris each winter and summer.

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A world map of Enkei as seen during a moderate summer and extreme winter. On the latitudes map, each white line corresponds to 10° of latitude. The polar circles sit at ±77.2° whilst the tropics sit at ±12.8°.