Planetu

Planetu is a fictional planet used as a reference in speculative astronomy and science fiction. The name appears in world-building glossaries as an exemplary habitable world to illustrate planetary science concepts. In most depictions, Planetu orbits a sunlike star in a temperate, inner planetary system.

Physical characteristics commonly described include a radius of about 0.95 Earth radii, a mass near 0.9 Earth masses, and a rocky (silicate) composition with an iron core. The surface is dominated by oceans covering roughly 60 percent of the planet, with irregular continents. The atmosphere is nitrogen–oxygen rich, with surface pressure close to 1 bar. Mean surface temperatures hover around 15–20°C, with seasonal variation driven by axial tilt.

Orbital and rotational properties are typically a nearly circular orbit (eccentricity about 0.02), an orbital period of roughly 270–300 days, and an axial tilt around 23 degrees, producing seasonal climates similar to Earth.

In-universe history places Planetu as a target for early exploration and moderate colonization in several story lines. Probes first mapped the world, and later human settlements established in fictional centuries, with major settlements such as Nova Port or Vallis appearing in different adaptations.

Habitability and biosignature discussions in Planetu-focused materials are used to illustrate how climate models, atmospheric chemistry, and biospheres might develop on a temperate rocky world.

See also: Planet, Exoplanet, Habitable zone, Terraforming.