Which is the most popular and well known comet of all times? Indeed, it is the Halley’s Comet. Records state that the Halley’s Comet has been observed by people over centuries. The Babylonians, Europeans and Chinese star gazers have seen this comet with their naked eye. It was assumed to be a long period comet originating from the distant Oort cloud. Its elongated orbit takes it near to the Sun and the powerful solar winds flung it out of our solar plane, beyond the orbit of Pluto. This comet was proven correct by the prediction of the astronomer Edmond Halley about its reappearance. Only 54 comets having an orbital period between 20– 200 years have been recognized. Halley’s Comet is the first amongst them. Shaped like a broom, it is the most viewed and is a spectacular apparition in the skies. Halley’s Comet is also responsible for the Orionid meteor shower in October when the earth passes through its debris stream and Eta Aquarid meteor shower in May. Let us learn in detail about this comet.
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Most of the apparitions of this comet have been in pre–historic times. English astronomer Edmond Halley first published his work on comets in the year 1705. He was the first to state that this was a periodic comet. His catalogue contained calculations about the orbits of 24 comets and he mentioned that the comets observed in 1531, 1607 and 1682 were one and it returned every 76 years. Edmond Halley predicted the return of this comet in 1758. However, he passed away in 1742. The comet returned late in 1758 and was sighted in March 1759. The comet was named Halley’s Comet in his honour. The earlier perihelion passages of Halley’s Comet were calculated using this information. Sighting of this comet have been reported from Greece around 467 and 466 BC but the Chinese astronomers have recorded its appearance in 240 BCE. Halley’s close approach to the earth has been noted on 10th April, 837 and apparitions were also noted in 1066 and 1301.
Observations made by Halley in 1705 about the Halley’s Comet include:
- This comet orbited around the Sun. It was a member of our solar system.
- Studies made in 1986 apparition states that the nucleus of this comet is ellipsoidal and measures about 15 km x 8 km x 8 km.
- Observations also include that this comet may have been a long period comet that has been perturbed by the gravitational field of giant planets and became a short period comet of less than 200 years of orbital period.
Halley’s Comet reached a magnitude of about 2.6 in the 1986 apparition. The 1003 apparition was the brightest apparition of this comet. The apparent magnitude of this comet was revealed at about 28.2 in 2003.
The perihelion distance (closest to the sun) of the Halley’s Comet has been noted at 0. 586AU.
The orbital period of the Halley’s Comet is 76 earth years approximately. This period changes due to the perturbations caused by the gravitational effects of the giant planets.
The comet, popularly known as the Halley’s Comet was recovered on 25th December, 1758 by Johann Georg Palitzsch (Prohlis, Germany). Palitzsch was a farmer and an amateur astronomer who used to observe the skies for comets and other celestial objects. This return of 1758–59 comet was a link to study the apparitions of this comet prior to its 1531 appearance.
A comet, now known as the Halley’s Comet had close approaches to the earth in the 19th century. However, it is expected to have a close approach to the planets Venus and the Earth and one close approach with Jupiter in the 21st century.
Perihelion date of Halley’s Comet is July, 2061. It orbits the sun every 75–76 years. Its last perihelion was on 9th February, 1986.
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