long-period comet

…than 200 years and the long-period comets with orbital periods longer than 200 years. The short-period comets were split into two groups, the Jupiter-family comets with periods shorter than about 20 years and the Halley-type comets with periods longer than 20 years but shorter than 200 years. In 1996 American…

…called near-Earth objects (NEOs)—and those long-period comets that make their closest approach to the Sun inside Earth’s orbit. Short-period comets complete their orbits in less than 200 years and so likely have been observed before; they generally approach along the plane of the solar system, near which lie the orbits…

Long-period comets have orbital periods greater than 200 years and usually much greater; they can approach from any direction.

…denotes that it is a long-period comet (period greater than 200 years), while “P/” denotes that the comet is periodic; i.e., it returns at regular, predictable intervals of fewer than 200 years. A designation of “D/” denotes that the comet is deceased or destroyed, such as D/Shoemaker-Levy 9, the comet…

…whether it is periodic or long-period. The system uses the year of the comet’s discovery, the half-month in the year denoted by a letter A through Y (with I omitted to avoid confusion), and a number signifying the order in which the comet was found within that half-month. Thus, Halley’s…

But some orbit solutions for long-period comets suggested that they were slightly hyperbolic, suggesting that they came from interstellar space. That problem would not be solved until the 20th century.

Some long-period comets did have orbit solutions that were slightly hyperbolic, barely above an eccentricity of 1.0. But a truly hyperbolic comet approaching the solar system with the Sun’s velocity relative to the nearby stars of about 20 km (12 miles) per second would have an…

…with the known orbits of long-period comets, which showed no concentration of comets that would have formed at that distance or in that direction. In addition, the total amount of gases that could be adsorbed on a sandbank cloud was not sufficient to explain the measured gas production rates of…

…in orbital energy for the long-period comets, with as many long-period comets ending in very long-period orbits as in very short-period orbits. Finally, van Woerkom showed that Jupiter would eventually eject all the long-period comets to interstellar space over a time span of about one million years. Thus, the comets…

…noticed that the number of long-period comets returning to the planetary system was far less than what his model predicted. To account for that, he suggested that the comets were physically lost by disruption (as had happened to Biela’s Comet). Oort proposed two values for the disruption rate of comets…

…known original orbits of the long-period comets.

…computed the rocket forces for long-period comets and found that there too the mean residuals were reduced. For the long-period comets, the rocket force was typically a few ten-thousandths of the solar gravitational attraction. Long-period comets tend to be far more active than short-period comets, and thus for them the…

…thought that short-period comets were long-period comets from the Oort cloud that had dynamically evolved to short-period orbits because of planetary perturbations, primarily by Jupiter. But astronomers who tried to simulate that process on computers found that it was very inefficient and likely could not supply new short-period comets fast…

…up to about 35°, whereas long-period comets have completely random orbital inclinations from 0° to 180°. Fernández suggested that the easiest way to produce a low-inclination short-period comet population was to start with a source that had a relatively low inclination. Kuiper’s hypothesized comet belt beyond Neptune fit this requirement.…

…the nucleus is large for long-period and Halley-type comets, which have made relatively few approaches close to the Sun, and very low, typically only a few percent, for short-period, Jupiter-family comets, which have made hundreds of returns, on average.