XYPlanet

XYPlanet is a hypothetical terrestrial exoplanet frequently used in astronomy education and research simulations to illustrate planetary formation, atmospheric evolution, and habitability boundaries. It is commonly described as orbiting a sun-like star in a fictional system designated Euxora, at a distance near 1 AU, which provides Earth-like insolation in many standard models.

Physical characteristics of XYPlanet vary by model, but it is typically depicted as a rocky world with a radius close to Earth's (about 1.0–1.2 R⊕) and a mass around 0.8–1.5 M⊕. In baseline representations, it hosts a tenuous atmosphere—often nitrogen-dominated with trace carbon dioxide—and a surface gravity suitable for habitability studies. The exact composition and thickness of the atmosphere depend on the scenario being demonstrated.

Orbit and climate models assume a near-circular trajectory (eccentricity < 0.1) with an orbital period of several hundred days. Climate outcomes are sensitive to atmospheric properties and greenhouse effects; some simulations yield temperate conditions with potential for liquid water, while others predict drier or more greenhouse-limited environments. The planet's hypothetical surface conditions are used to explore how small changes in composition, albedo, or stellar input influence habitability.

Uses and significance: XYPlanet serves as a standard reference in teaching planetary formation, atmospheric retention, detection methods, and habitability assessments, appearing in textbooks, classroom simulations, and software datasets. It also functions as a placeholder in fiction and educational media when illustrating exoplanet catalogs.