Halleytype

Halleytype (also Halley-type) is a designation used in cometary astronomy to classify short-period comets with orbital periods typically between about 20 and 200 years. The class is named after Halley's Comet (1P/Halley), the best-known member and the prototype of the group.

Orbits of Halley-type comets are generally highly elliptical and can have a wide range of orbital inclinations, including retrograde trajectories. Perihelion distances commonly fall within the inner Solar System, allowing visits roughly once a decade to two centuries.

Most Halley-type comets are believed to originate from the Oort cloud, from which planetary perturbations can send them toward the Sun; some may have originated from the trans-Neptunian region or be fragments of longer-period comets. They occupy a dynamical niche between Encke-type comets (short-period with P less than 20 years) and long-period comets (P greater than 200 years).

Notable Halley-type comets include 1P/Halley and 109P/Swift-Tuttle. The study of HTCs contributes to understanding cometary nuclei composition, evolutionary processes, and the early Solar System.