Halley s comet

Alkanes have the general molecular formula C H2 +2 The srmplest one methane (CH4) rs also the most abundant Large amounts are present rn our atmosphere rn the ground and rn the oceans Methane has been found on Juprter Saturn Uranus Neptune and Pluto and even on Halley s Comet... 

Formaldehyde cyanohydrin was detected in Halley s comet by the Vega I space probe (27). 

Hoek, M.J.v.d., The Treatment of the Problems Due to Hypervelocity Impact During a Fast Fly-By (57 km/s) of Halley s Comet, European Space Agency Report No. ESA SP-153, Paris Cedex, France, pp. 121-129, October 1979. 

Water can be found, in all three aggregate states, almost everywhere in the universe as ice in the liquid phase on the satellites of the outer solar system, including Saturn s rings and in the gaseous state in the atmospheres of Venus, Mars and Jupiter and in comets (as can be shown, for example, from the IR spectra of Halley s comet). The OH radical has been known for many years as the photodissociation product of water. 

The mass of Halley s Comet is about 1014kg, and thus its mean density is only 200 kg/m3. The rate of loss of material has been estimated as 5,000 kg/s. The nucleus is loosely packed and exhibits point craters and chasms from which gas and dust escape. These emissions consist mainly of water vapour (—80% by volume) as well as 6% CO, < 3% C02, -2.5% CH4, -1.2% NH3 and < 6% N2 (Flechtig and Keller, 1987). At the point where Giotto came nearest to the comet, the estimated amount of water being ejected was close to 15,000 kg/s, while that of dust particles was between 6,000 and 10,000 kg/s. Ions derived from water were detected in the... 

In fact the method may be strong in getting information on neutrons in comets, and in fact at our laboratory a mass spectrometer probe for the cometary mission of Halley s comet is prepared. But the scenario is a little bit different. Of course the gas tail of the comet has a very complex chemistry and you have gradients in concentrations and change in direction with the radiation field, that the ultimate goal would be to trace back the so-called OH. In order to get these, of course you have to translate or to imravel the entire chemistry — you measure a gas constituent which was produced by possibly not very well known processes. You have to evaporate first the material from the comet, then it is exposed to the UV radiation field of the sun, it s processed photo-chemically, it may undergo some reactions, so that would be very difficult. But there is a chance to get some information. 

Geiss J. (1988) Composition in Halley s comet clues to origin and history of commentary matter. Rev. Mod. Astron. 1, 1-27. 

A contemporary and friend of Newton, Halley, observed a comet in 1682 and suspected others had observed it many times before. Using Newton s new mechanics (laws of motion and universal law of gravity) Halley calculated that the comet would reappear at Christmas, 1758. Although Halley was dead, the comet reappeared at that time and became known as Halley s comet. This was a great triumph for Newtonian mechanics. 

A poster advertising a lecture on campus provided this opportunity for humor Professor Elizabeth Sewell will discuss the latest appearance of Halley s Comet in room 104. Under the announcement a local wit had scribbled, Shall we reserve room 105 for the tail Or take the case of this startling headline Calf Born to Rancher with Two Heads. ... 

Like the appearance of Halley s comet every 76 years, the properties of the elements repeat in a regular way when they re arranged in the periodic table. When you understand the table s arrangement, you ll be able to explain why silver and potassium don t act in the same way. The repeating patterns in the periodic table are the key to differences as well as similarities in behavior and properties of all the elements. 

Mendeleev s insight was a significant contribution to the development of chemistry. He showed that the properties of the elements repeat in an orderly way from row to row of the table. This repeated pattern is an example of periodicity in the properties of elements. Periodicity is the tendency to recur at regular intervals— like the appearance of Halley s comet every 76 years. 

The "bright new star" was actually a comet, known today as Halley s comet. Halley s comet reappears on a regular basis every 76 years. Each of its appearances has caused fear and amazement among people around the world. Indeed, comets are among the most dramatic of all astronomical events. 

Comets are masses of frozen gases, cosmic dust, and small rocky particles. Astronomers think that most comets originate in a dense comet cloud beyond Pluto. Comet consists of a nucleus, a coma, and a tail. A comet s tail always points away from the sun. The most famous comet, Halley s Comet, is named after the person whom first discovered it in 240 B.C. It returns to the skies near earth every 75 to 76 years. 

Newton showed that, under the inverse-square attraction of gravitational forces, the motion of a celestial object follows the trajectory of a conic section. The stable orbits of the planets around the sun are ellipses, as found by Kepler s many years of observation of planetary motions. A parabolic or hyperbolic trajectory would represent a single pass through the solar system, possibly that of a comet. The better known comets have large elliptical orbits with eccentricities close to 1 and thus have long intervals between appearances. Halley s comet has e = 0.967 and a period of 76 years. 

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