Kesari tours for However, if a comet is out of sync with Earth, as was Hale-Bopp, humans can only watch the action from their seats near the back row. Long-Period and Short-Period Comets Astronomers like to divide comets into two major groups long-period and short-period ones. Long-period comets take more than years to complete a single orbit, while shortperiod comets have an orbital period of years or less. In terms of performance and productivity, long-period comets are wild and powerful in contrast to short-period comets, which are tame and weak. Long-Period Comets Many of the individual comets observed over the last few hundred years have been in extraordinarily long orbits with periods in the hundreds, thousands, and even millions of years. Indeed almost all the great comets in history are long-period comets. Long-period comets have no particular preference for the plane of Earth’s orbit, with many cutting across it at very sharp angles. Kesari tours 2016.