Halley’s Comet comes close to the Sun around every 75.3 years, but the period varies somewhat due to changes in the comet’s orbit.
Halley’s Comet became visible to the naked eye in the night sky this day in 240 BC, and remained so for a few more days. The event was noted down in China and this is considered the first recorded appearance of Halley’s Comet in general.
Halley’s Comet comes close to the Sun around every 75.3 years, but the period varies somewhat due to changes in the comet’s orbit. When it is closest to the Sun, Halley’s Comet passes between the orbits of Venus and Mercury, but when it’s the farthest away, it is located beyond Neptune’s orbit, at a distance of around 5.25 billion km. The mass of Halley’s Comet is around 220 billion tons.
As far as it is known, astronomers in classical antiquity and the middle ages didn’t understand that Halley’s Comet periodically passes near Earth and the Sun; they considered its appearances to be different comets (this applies to the mentioned Chinese record). It was only the British astronomer Edmond Halley who discerned the truth. The comet is slated to return near Earth in 2061.