Long-period comets have periods of over 200 years.The longest would probably be somewhere around a million years (comparable to the orbital periods of objects in the Oort cloud); much longer than that, and it will go away far enough to be captured by the gravitational field of other stars.
A comet with a period of 200 years or more.
600,000,000,000,000,000,000,000,000,000
That depends on what you call 'long' or 'short'. Halley's period is in the neighborhood of 75 years, give or take a few years. Since that's short enough for two perihelions to occur within a single human lifetime, I guess it ought to be considered a short period.
Hyakutake is a long-period comet. Before its most recent passage through the solar system, its orbital period was about 17,000 years, but the gravitational influence of the giant planets has increased this period to 102,070 years.
Shoemaker-Levy 9 had a short period, as it was a comet that was first discovered in 1993 and eventually collided with Jupiter in 1994. The comet had been fragmented by Jupiter's gravity during a previous close approach, leading to its eventual collision with the planet.
A comet with a period of 200 years or more.
A comet with a period of 200 years or more.
Long period comet
Comet (C/2010 X1 (Elenin)) is a long-period comet.
600,000,000,000,000,000,000,000,000,000
The orbital period of Halley's Comet is about 75.3 years.
each 76 years
Between 74 and 76 years.
That depends on what you call 'long' or 'short'. Halley's period is in the neighborhood of 75 years, give or take a few years. Since that's short enough for two perihelions to occur within a single human lifetime, I guess it ought to be considered a short period.
A short period comet.
Halley's comet has a period of 76 years.
Not more than 200 years - less than 200 years. As to the "why", that's because this is how "short-period" vs. "long-period" is defined. Any comet that takes less than 200 years for one revolution is defined as short-period.