Halley's Comet, officially designated as 1P/Halley, is a short-period comet visible from Earth every 75–76 years. Here are some key details about this celestial phenomenon:
Discovery and Naming
- Halley's Comet was named after the English astronomer Edmond Halley, who in 1705, calculated its orbit and predicted its return. Halley's work on comets helped him realize that the comet sightings in 1531, 1607, and 1682 were likely the same object.
- The comet has been observed and recorded by astronomers since at least 240 BC, with Chinese, Babylonian, and medieval European records documenting its appearances.
Physical Characteristics
- The nucleus of Halley's Comet is relatively small, with an estimated size of about 15 by 8 kilometers. It is composed of dust, water ice, and other frozen gases like carbon dioxide and methane.
- As it approaches the Sun, the heat causes the comet's ices to sublimate, creating a coma, which is a temporary atmosphere, and two tails: a dust tail and an ion tail.
Orbit and Appearances
- Halley's Comet orbits the Sun in a highly elliptical path. Its closest approach to the Sun (perihelion) is about 0.6 AU (Astronomical Units), while its aphelion takes it to around 35 AU, beyond the orbit of Neptune.
- Notable appearances of the comet include:
- 1066 AD - Its appearance was recorded in the Bayeux Tapestry, which depicts the Battle of Hastings.
- 1910 - During this passage, Earth passed through the comet's tail, leading to widespread panic over potential poisoning by cyanogen gas.
- 1986 - The last time Halley's Comet was visible from Earth, it was less spectacular due to its greater distance from Earth. Several spacecraft, including Giotto and Vega, were sent to study the comet up close.
Historical Significance
- The comet has been considered a harbinger of change or disaster in many cultures. For example, its appearance in 1066 was interpreted as an omen before the Norman Conquest of England.
- It played a crucial role in the development of cometary science, as Halley's prediction of its return was the first time a comet's periodicity was recognized.
Next Appearance
- Halley's Comet is next expected to be visible from Earth in 2061. Given its long orbital period, each return is an event of significant interest for astronomers and the public alike.
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