Halley's Comet was the Sol system's best known comet, with a
regular orbit of approximately 76 years. Halley's Comet was
often visible from Earth's surface when nearing perihelion, its
point of least distance from Sol. Two of Halley's appearances
marked the years of the birth (1835) and death (1910) of the
famous American writer Samuel Clemens. A time travel incident
brought him from San Francisco in August 1893 to a short visit
on the decks of the USS Enterprise-D in 2369. Clemens was
curious as to whether the starship had ever reached Halley's
Comet. (TNG: "Time's Arrow, Part II") In 1996, the Griffith
Observatory featured an exhibit about Halley's Comet. In order
to get from Rain Robinson's lab to the lobby, one had to "go
right down the hall, take a left at Mars, right at Halley's
Comet and then just keep going straight ahead past the soda
machine". (VOY: "Future's End") After 1910, Halley's Comet's
perihelia occurred, or will occur, on: Given the gravitational
effect of the Sol system planets on the come