Halley's Comet
Halley's Comet, officially known as 1P/Halley, is a short-period comet visible from Earth every 75–76 years. It is named after the English astronomer Edmond Halley, who in 1705, calculated its orbit and predicted its return. Here are some key details about Halley's Comet:
Discovery and Historical Observations
- Observations of Halley's Comet go back over 2,000 years. Its earliest recorded sighting was in 240 BC by Chinese astronomers.
- The comet was visible during significant historical events, such as the Battle of Hastings in 1066, depicted in the Bayeux Tapestry.
- Edmond Halley recognized that the comets observed in 1531, 1607, and 1682 were likely the same object returning periodically. He predicted its return for 1758, which occurred posthumously.
Orbital Characteristics
- Its orbit is retrograde and elliptical, taking it from just inside the orbit of Venus to beyond Neptune.
- The perihelion (closest point to the Sun) of Halley's Comet is about 0.587 AU, and its aphelion (farthest point from the Sun) is about 35.1 AU.
- The comet's orbit is influenced by gravitational perturbations, particularly by Jupiter, which can alter its period slightly.
Physical Properties
- Halley's Comet has an estimated nucleus size of 15 km × 8 km × 8 km.
- It is composed of water ice, frozen gases, and dust. When it approaches the Sun, the ice sublimates, creating the visible tail.
- The comet's tail can stretch over tens of millions of kilometers, and its direction is always away from the Sun due to solar wind.
Notable Returns
- Its return in 1910 was particularly memorable because Earth passed through the comet's tail, causing public panic.
- The 1986 return was the first time Halley's Comet was visited by spacecraft, including Giotto, Vega 1, and Vega 2, which provided detailed images and data of the nucleus.
- The next predicted perihelion passage is in July 2061.
Cultural Impact
- Halley's Comet has been a source of inspiration in art, literature, and culture. For instance, it's depicted in the Bayeux Tapestry and inspired Mark Twain, who was born and died during its appearances.
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