Periodic Orbit of Halley's Comet

Discovered by : Edmond Halley

Discovered in year : 1705

Comet Halley or more popularly known as Halley's Comet is a periodic comet and can currently be seen every 75–76 year. It was officially designated as 1P/Halley. It is one of the most famous periodic comets as is clearly visible to the naked eye as compared to others and also because it is certain to return within a human lifetime.Halley's Comet last appeared in the inner Solar System in 1986, when it became only the second comet to be visited by spacecraft. It is predicted appear on July 28, 2061. Though Halley is a periodic comet, its orbit suggests that it originated in the Oort cloud, the reservoir for long–period comets with orbits lasting thousands of years, but was dragged into the inner Solar System by the gravity of the planets. Halley's apparitions over the past thousand years have been interpreted as omens and portents for several historical events, including the Battle of Hastings in 1066 and the 1456 Siege of Belgrade.

History of the Discovery

During its returns to the inner solar system, Halley's Comet has been observed by astronomers since at least 240 BC, but it was not recognized as a periodic comet until the eighteenth century when its orbit was computed by English astronomer Edmond Halley, after whom the comet is now named. Edmond Halley (1656–1742) was an English astronomer and mathematician. He is particularly noted as the first astronomer to predict the return of a comet

On the basis of Newton's theory, Halley calculated the orbit of the great comet of 1682 since known as Halley's comet and predicted its return in 1758. In his 1705, 'Synopsis of the Astronomy of Comets', Halley used Newton's new laws to calculate the gravitational effects of Jupiter and Saturn on the orbits of comets. There had been comet sightings in 1456, 1531, 1607, and 1682 which intrigued Halley. Based on Newton's Law and after examining historical records, he came to the conclusion that these sightings belonged to one and the same comet. He determined that  the orbital elements of a second comet which had appeared in 1682 were nearly the same as those of two comets which had appeared in 1531 (observed by Petrus Apianus) and 1607 (observed by Johannes Kepler). Halley thus concluded that all three comets were in fact the same object returning every 76 years, a period that has since been amended to every 75–76 years. After a rough estimate of the perturbations the comet would sustain from the attraction of the planets, he predicted its return for 1758. Halley did not live to see the comet's return, having died in 1742.

Role of the Discovery of Halley's Comet in Human Life

• The confirmation of the comet's return was the first time anything other than planets had been shown to orbit the Sun.

• It was also one of the earliest successful tests of Newtonian physics and a clear demonstration of its explanatory power

• Study of Halley's Comet had enabled Humanity to better understand the vast space around us about which we only know as much as a speck of dust.