Before the seventeenth century, comets were considered portents-warning shots fired at a sinful Earth from the right hand of an avenging God. However, in the post-Newtonian era, when their paths were understood to intersect that of the Earth, they were considered actual agents of destruction. Experts have described comets as the carriers of both life-seeds to the early Earth and horrific missiles that will one day snuff out life as we know it. At one time or another, people have blamed comets for war and held responsible for the deaths of men, the birth of good wine, the London fire of 1666, severely cold weather, etc . . . If one central theme runs throughout history of comets, it must be the public concern they have commanded. Comets are ancient objects, formed in the outer reaches of the Solar System from the ice of gases such as methane, water vapor, and ammonia, combined with dust from primitive rock compounds. Sometimes comets are described as "dirty snowballs" because they are icy lumps, or wandering icebergs. Comets are relatively tiny- just a few miles across on average. Their nuclei are very different from glowing balls of light, with multimillion-mile-long tails. This is one reason comets occasionally visit the inner Solar System. Astronomers divide comets into long-period types with orbits of more than 200 years and short-period types with orbits of less than 200 years (as cited in Branley 1988 p. 43). All comets begin their journey as long- period types. Gravitational fields of planets then capture long- period comets. Comets can have orbits at any angle because they can come from any region. Once comets are captured, they fall into line with the movement of planets, staying close to the ecliptic, orbiting the sun in the same direction as the planets. One exception is Halley's Comet. It is a short-period comet with an orbital period of about seventy-six years- known as retrograde orbits (as cited in Branley 1988 p.
A Comet looks like a star with a tail. Some comets do not have tails, and look like hazy, round spots of light. But most comets have three parts; a nucleus, a head, and a tail. ... The most famous comet to be seen as a brilliant, and inspiring was Halley's comet, in 1910. ... in 1456, Halley's comet frightened everyone in Europe so much that Christian churches added a prayer to be saved from "the Devil, and the comet." ...
Observations of the comet of 1577 by Tycho Brahe demonstrated that comets were more distant than the moon. ... The material released is lost to the comet, and therefore the lifetimes of comets must be limited. ... Comets have even hit a planet's surface. ... COMET TAILS A comet normally has two tails. ... COMET TRAJECTORIES Comets are often close to the sun and sometimes to the earth at the time of discovery. ...
Comets are not on fire. As they near the sun, the sun's heat melts the comet's ices and releases dust particles which are most evident as the comet's tail. ... Typical comets remain visible for periods of several weeks up to several months. Comets are the long-distance runners of the solar system. ... Most meteoroids- fragments from asteroids and dust from comets, remain in outer space. ...
- Observations of a comet in 1577 - By measuring the parallax for the comet, he was able to show that the comet was further away than the Moon... - this contradicted the teachings of Aristotle - Aristotle thought that comets were atmospheric phenomena ("gases burning in the atmosphere" was a common explanation among Aristotelians). As for the case of the supernova, comets represented an obvious change in a celestial sphere that was supposed to be unchanging; furthermore, it was very difficult to ascribe uniform circular motion to a comet... - Brahe's observations of the new star ...
Whitemire and Matese came up with a theory that the killer comets are on a planet, not a star. ... Most comets remain unnoticed in the deep freeze of the Oort cloud. ... Comets entering the inner solar system have an equally haphazard pattern. ... The comets were similar in their orbits. The astronomers concluded that something 3 to 5 times larger was bouncing comets our way. ...
As its orbit nears the Sun it will pass through the Oort Cloud, a patch of billions of comets which orbit the Sun beyond Neptune. The gravitational force of Nemesis will then be able to send some of these comets in random directions. ... The size of the suspected comet was then found by comparing the amount of iridium found at Gubbio with the known levels in other comets. ... His reasoning for this was that the ratios of the isotopes in this element differ greatly between the Earth's crust and comets. ... This finding gave another supporting argument for the theory that a comet was re...
Comet Borrelly Immediately after the flyby of asteroid Braille, Deep Space 1 was given a new objective. This time it was to fly near comet Borrelly. However, on the way to this comet a device called the DS-1, an orientation instrument, failed [1] and that made it even harder to continue successfully. ...
Asteroids and comets are also in part of our solar system. ... Comets are sometimes called dirty snowballs or "icy mud-balls". ... Below is a picture of a comet called Halley's Comet that has records of sightings going all the way back to 240 B.C. by ancient Chinese astronomers. ...
Chinese could predict eclipses by analyzing the motions of the moon COMETS There are Chinese records of comet halley going back to at least 240 BC Comets are a mixture of ices and dust and orbit around the solar system When they get near the sun, the ice melts, leaving behind a tail. ...
