What is the size of Halley's comet?

Halley's comet has a mean diameter of 11 kilometers across. On average, it passes by Earth between every 75 to 76 years. In 1910, Halley's comet came as close as 13.9 million miles.

The first written observations of Halley's comet are found in Chinese manuscripts from 239 B.C. Additional recorded sightings date back to 164 B.C. and 87 B.C. Halley's comet is named after astronomer Edmond Halley, who wrote about the comet's passage by Earth in 1531, 1607 and 1682. In the 20th century, the comet passed by Earth in 1910 and again in 1986. In the 21st century, Halley's comet is expected to pass by Earth in 2061.