Planet Profile: Arlena

This planet profile was sent to us by Nathan Hall. Kepler 186f is a real planet, but Nathan has mixed real-life astronomical observations with his own imagination to create this fictional depiction.

oceanworldName: Arlena (Kepler 186f)
Star: Kepler 186
Constellation: Cygnus
Distance from Earth: 500 light years
Average Year: 129 Earth Days
Average Day: Unknown
Size: About the same as earth
Gravity: 1g (same as earth)
– No seasons
– No visible land
– Huge trees that are the main and only ecosystem of the planet
– Large insects and arachnids due to large amounts of oxygen
– Massive oceans with thousands of trees gathered so closely, they look like islands
– Many varieties of life forms due to the vast immensity of the trees
– Intelligent feline humanoids with a clan society (one clan on each tree) that calls themselves Arlenians (which means People of the Trees in their language).


Kepler 186f is an aesthetically pleasing world with massive trees and no visible land. It is called Arlena by the indigenous Arlenians. The partially submerged trees grow in shallow waters, forming forests and coppices that look like islands from above.

Arlena is a host to a vast variety of aquatic and air based life forms, including massive, truck sized centipedes and horse sized dragonflies, which are the result of large amounts of oxygen produced by the Arlena trees and are often used by the Arlenians as riding and cargo beasts. The Arlena trees are the back bone of the Arlenian civilization, each tree supporting an entire family clan of about 1,000 individuals. The Arlenians set up apartments, houses and mansions on the trunks and branches of their trees based on social and age class, with the eldest leading the clan. As there is no land, they do not have farms. Another reason for the lack of farms is the Arlenian desire to live ‘natural’ lives, inspired by an ancient religion that had no deities. The religion said that if you lived naturally and became part of the ecosystem, your spirit would be sent to the stars and become one with them. That religion was abandoned due to the development of science and the arrival of super advanced aliens, but its main teachings remain culturally important.

For electric power, the Arlenians set up massive power rigs on the oceans, where the sun is unobstructed and the winds and currents are the strongest. They also serve as space ports and harbors for navigation and transportation on and off world. Before their discovery of electricity, they used the sap of the glow flower, a plant with powerful bioluminescence that grows on the branches of trees and holds special significance in Arlenian society. The sap of the glow flower is a living jumble of millions of cells which automatically glow during night due to a chemical response.

Article by Nathan Hall.

Find out more about the indigenous Arlenians by reading Nathan’s alien profile.

  • Anon

    Great world building Nathan. The bioluminescent sap is a pretty cool idea.

  • avrorik369 .

    Nice idea. Could use it if a planet with no dry land yet non-bathypelagic pops up in the generator.

  • Nova

    I have some questions: Which consequences will have an increased level of oxygen in the atmosphere on plant and animal life other than larger insects? Is there a maximum level above which life becomes impossible? And: Could sentient life forms on such planets use fire or would this lead to total destruction, because oxygen is flammable?

    • Logan Testa

      I’m not a biologist, so I cant answer your first question. However, i might be able to answer your second. While oxygen is required for the combustion of many substances, it is only flammable when mixed with other gasses and in the correct stoichiometric ratio (moles of O2:moles of whatever you are burning). Oxygen doest burn by itself, but it is a powerful oxidizer to allow other substances to burn. The fires on this planet might be very large and last very long, because they have lots of oxygen at their disposal, but the flame would not ignite all the oxygen on the planet all at once, unless that oxygen was also mixed with some flammable gas, like methane, at a proper stoichiometric ratio. Please correct me if i am wrong.

  • FoxyThePirate117

    Can you make underwater trees that can stand without support even under 5 gees of gravity(In this case,water)?

  • TeVaughn

    How is this planet habitable?