Long-period comet

Extinction

Jupiter-family comets and long-period comets appear to follow very different fading laws. The JFCs are active over a lifetime of about 10,000 years or ~1,000 orbits whereas long-period comets fade much faster. Only 10% of the long-period comets survive more than 50 passages to small perihelion and only 1% of them survive more than 2,000 passages. Some asteroids in elliptical orbits are now identified as extinct comets. Roughly six percent of the near-Earth asteroids are thought to be extinct comet nuclei.