Langeperiodische

Langeperiodische is a German adjective meaning long-periodic. In astronomy, the term is commonly used in the compound langeperiodische Kometen to denote comets whose orbital periods exceed about 200 years. The phrase appears in German-language science writing and education about comets.

These comets are believed to originate primarily from the distant Oort cloud, a vast reservoir of icy bodies surrounding the outer solar system. They enter the inner solar system on highly elongated orbits, with semi-major axes spanning thousands to tens of thousands of astronomical units. Their orbital periods can stretch across centuries or millennia, and their trajectories are often highly inclined, sometimes retrograde.

Observationally, langeperiodische comets are challenging to study because they spend most of their time far from the Sun and are faint when near aphelion. They are typically discovered when they approach perihelion and brighten, bringing them into the range of naked-eye visibility. Their paths are sensitive to gravitational perturbations from planets, the galactic tide, and passing stars, meaning that their orbits can change over time and predictions of return can be uncertain.

Notable examples include Comet Hale-Bopp (C/1995 O1) and Comet Hyakutake (C/1996 B2), among others. These objects provide valuable information about the early solar system’s volatile materials and isotopic compositions. Studying langeperiodische comets also informs models of the Oort cloud’s structure and the dynamical evolution of cometary bodies within the solar system.

See also: Short-period comets, Oort cloud, comet taxonomy.