Short answers, pulled from the story.
Chinese astronomers recorded a comet in 240 BC, marking the first confirmed sighting of Halley's Comet in human history. This entry describes the object moving from east to north and appears in the Records of the Grand Historian.
Edmond Halley used Newton's laws of gravity to calculate the orbits of three comets and concluded they were the same object returning every 76 years. His 1705 Synopsis of the Astronomy of Comets predicted its return for 1758 after accounting for gravitational pulls from Jupiter and Saturn.
The nucleus is pitch black with an albedo of 0.04 and reflects only 4% of sunlight hitting it, similar to coal. The shape resembles a peanut or potato rather than a perfect sphere and contains surfaces composed largely of dusty non-volatile materials.
Spectroscopic analysis discovered toxic cyanogen gas in the comet's tail, leading press speculation that life on Earth could be endangered by this substance. Public panic buying of gas masks occurred despite scientific reassurances, and quack anti-comet pills were sold to fearful consumers.
The next perihelion occurs on the 28th of July 2061 when the comet reaches its closest point to the Sun. Earth approach happens one day after perihelion on the 29th of July 2061 with an apparent magnitude expected to reach negative 0.3.