Edmund Halley and Halley’s Comet – Astronomy Essay
Edmund Halley was born on the twenty-ninth day of October 1656 in Haggerston, Shoreditch, England. As a young child, he was an avid astronomer. Halley showed remarkable interest in classics and mathematics. During his studies at Queen’s College Oxford, he was steadily
becoming an expert astronomer. At the age of 19, Halley assisted Flamsteed, a wealthy man, with astronomy observations. Flamsteed commended Halley about his talent and dedication in a publication, Philosophical Transactions of the Royal Society. Throughout his studies at Oxford, Halley continued to embark on various important observations ranging from subjects of Mars, the Moon, Mercury, comets and constellations. Although Halley continued his observations, it is uncertain why Halley’s studies did not show importance because he gave up his studies. Throughout his career, Halley committed himself to science and discovery of astronomy. With the financial support provided through his father, Halley continued to build upon a notable reputation. His reputation had spread and support was evident when King Charles II submitted a letter to the East India Company requesting them to transport both Halley and an associate to St. Helena.
While stationed at St. Helena for eighteen months, Halley continued to catalog the southern hemisphere constellations in relation to Flamsteed’s northern hemisphere constellation catalog. In addition to his cataloging, Halley discovered a star cluster in Centarus. For the next several years, Halley’s reputation continued to blossom. He was increasingly become a well-known and leading astronomers. It is interesting to note that although Halley did not complete his degree at oxford, his outstanding reputation was recognized by King Charles II when he commanded Halley graduate without taking the degree examinations. Halley’s remarkable accomplishments all ensued before the age of 22.
Halley became interested in the path of the planets. By assessing Kepler’s third law, which states the ratio of the squares of the periods of any two planets revolving about the Sun is equal to the ratio of the cubes of their mean distances from the Sun, he believed that through Kepler’s third law that planets had an ecliptical orbit. Mathematically Kepler’s third law is defined as (T1/T2)2 = (r1/r2)3. Although, many did not support his theories, Sir Isaac Newton, a good friend of Halley, had attained proof that this was quite possible. Halley was confident in his support for Newton that he encouraged Newton to write Principia Mathematica, and in addition, Halley financially supported Newton’s publication. It is through Halley’s support and encouragement that one of the most renowned publications, Principia Mathematica, was possible. Later Halley began to examine the path of comets.
Although Newton believed comets followed a parabolic path, Halley predicted through Newton’s newly devised law of universal gravitation and motion that the comet of 1682 was in fact the same comet which appeared in 1531 and 1607. He formulated that the same comet would resurface December 1758. Halley died before he could view the return of the comet of 1758. The comet was later named in honor of Halley for his discovery. His prominent prediction of the comet supported his theory that comets in fact follow an ecliptic path through orbit. He essentially revealed that the comet has a periodicity of seventy-six years.
There have been five explorations of the Comet, three by the former USSR and two from Japan. Spacecraft Vega -1 and Vega-2, launched by the USSR in 1984, did a flyby of the Comet. Each spacecraft was equipped with a Halley flyby probe and a Venus descent module. Vega captured 1500 images of the comet’s nucleus at a distance of 8000 km. In addition, Giotto, another USSR mission, was launched on July 2, 1985. It approached within 540km +/- 40 km of the comet’s nucleus on March 13, 1986. Giotto’s mission consisted of several objectives: (1) obtain color photographs of the nucleus; (2) determine the elemental and isotopic composition of volatile components in the cometary coma, particularly parent molecules; (3) characterize the physical and chemical processes that occur in the cometary atmosphere and ionosphere; (4) determine the elemental and isotopic composition of dust particles; (5) measure the total gas-production rate and dust flux and size/mass distribution and derive the dust-to-gas ratio; and, (6) investigate the macroscopic systems of plasma flows resulting from the cometary-solar wind interaction. Giotto was equipped with a multicolor camera which transmitted images to Earth before it was severely damaged by high speed dust or wind. Japan also contributed to the research of the Comet. The Japanese mission consisted of two similar spacecrafts, a test spacecraft called Sakigake and a Comet Halley encounter spacecraft called Suisei. The mission for Sakigake and Suisei was to fly by Halley’s Comet and study its effects on space environment. Suisei carried two prevalent scientific experiments, a UV imager (UVI) and a plasma experiment (ESP). The experiments were used to observe the solar wind plasma and cometary ions. Suisei passed the Comet twice on March 1 and March 8 of 1986. Although at this time, Suisei was unable to record anything due to the elongation angle. UV images of the comet’s hydrogen coma were documented continuously from November 26, 1985 until April 15, 1986. Suisei returned up to six UV images a day of Halley’s Comet. On March 8, 1986, the UVI was shut off and the solar wind instrument was activated, which was carried by Sakigake. Sakigake was equipped with three scientific experiments, a plasma wave probe (PWP), a solar wind experiment (SOW) and a magnetometer (IMF) Sakigake had a cometary flyby on March 11, 1986 The purpose the wave probe was to measure the solar wind and magnetic field as it flew by Halley’s Comet. Even though Sakigake passed Halley’s Comet it was did not carry any imaging instruments. When the SOW was activated cometary water, carbon monoxide and carbon dioxide ions were detected.
Through the Sakigake spacecraft, the beginning of Halley’s Comet physical nature was unwinding. The nucleus is 16 x 8 x 8 km. Halley’s nucleus is dark. “It’s albedo is only about 0.03 making it darker than coal and one of the darkest objects in the solar system.” (Comet Halley, 2001) The density is low roughly 0.1 gm/cm3. It is probably porous maybe due to the its composition consisting of dirt or dust that are the remnants of the ice which has sublimed. Halley’s orbit is regular. It is predicted to return in 2061. This is accountable due to its period of 76 years. Halley’s Comet distance is equivalent to 0.587 AU. Its orbital eccentricity is 0.967. The orbital inclination is 162.24°. Halley’s orbit is retrograde, orbital motion in a clockwise direction. As earlier indicated, Halley’s Comet in fact has an eclipical orbit.