Aren′t Comets just dirty snowballs? Possibly, as comets are icy celestial object which rotates the sun in a highly eccentric elliptical orbit, which orbital periods range from several years to thousands of years and some, possibly as many as several million years.

As a comet passes closer to the sun, it warms and begins to produce gasses which creates around the comet a visible atmosphere called a coma and sometimes a tail. This phenomena is due to the effects of the solar wind and solar radiation acting upon the nucleus of the comet. At times during the comet′s approach to the sun, this warming trend may causes a huge and sudden outburst of gas and dust, during which, the size of the coma greatly increase for a period of time. Although the solid nucleus of comets are generally less than 37 miles (60 km) across, the coma may be thousands or millions of miles across, even to an extent that the size of the comet appears larger than the Sun. Some Ion tails have been observed to be one AU, (one astronomical unit, or 93 million miles).

The nuclei of a comet is made up of ice, dust and small rocky particles, ranging in size from a few hundred meters to tens of kilometers across. When warmed by the sun, the coma may expand to be up to fifteen time the diameter of the earth and the tail may stretch as far as the distance from the sun to the earth, which on an average, is 93 million miles (150 million kilometers).

Most comets enter the inner solar system with little fanfare, in fact, most require the aid of a telescope or in the least a pair of binoculars to observe even faint light from these celestial objects.

Sometimes, when sufficiently bright, a comet may be seen from the Earth without the aid of a telescope and may have a visible apparition which traverses an arc of 30° across the sky, (or the width of about two hands). Comets have been observed and recorded since ancient times by many cultures, long before the invention of the telescope.

While there is evidence of the probity of visual aiding that occurred in ancient times, the modern invention of what is now known as the telescopes came about in the 1500s and immerged through the craftsmanship and technology in the science of optics from the developments of spectacles. The first patent application in 1608 was by Hans Lipperhey a Dutch spectacle maker who began using lenses to magnify distant objects. Although most telescopes were originally used for Earth-bound observation such as surveying, military tactics and other purposes, it was not long before a small group of astronomers turned there attention outward away from the earth to examine celestial objects. Even though the exact person who invented these long range visual aiding devices is debated, there were several who during the same time also began designing the first models of telescopes.

In 1609, Italian astronomer Galileo Galilei significantly improved the design and was the first to use it for astronomy. Galileo Galilei (1564-1642), after hearing about what Lipperhey called the Danish Perspective Glass constructed his own telescope and not long after, he demonstrated his telescope in Venice, which demonstration earned him a lifetime lectureship. After Galileo′s initial success, he then focused on refining his instrument from 3X to 8X, but not stopping there, he continued his refining process until his telescope achieved 30X magnification.

However, in the amazing story about Galileo, by no means was the telescope the only technology that he used. In fact, Galileo skillfully printed books and included the design of his telescopes in his books, and then he would present his research in printed form to the learned community.

However, this is in no way the story of a lone thinker who through his examinations with his telescopes and subsequent theorizing, was able to slowly piecing together an entirely new model of the cosmos. NO, it is totally to the contrary, as there was a large group of individuals in the early 1600s who took the newly created telescopes and pointed them toward the heavens.

Unlike those other observers, Galileo, instead used another new technology, the printing press to rapidly published his findings. In a larger way, Galileo understood the importance and significance of his celestial observations more so than did his contemporaries. Therefore, it was this understanding, and foresight to publish, that made Galileo's ideas stand the test of time and become the one who even today, we learn about as the most prominent of all the other important figures in the study of Astronomy and the one person whose name became synonymous with the telescope.

Furthermore, in 1610 CE, the four largest moons of Jupiter were discovered by Galileo.

Others followed, including Johannes Kepler′s Astronomical Refractor in 1611 using two convex lenses that improved astronomical observations.

Isaac Newton′s Reflecting Telescope, which he invented in 1668, which used mirrors instead of lenses to gather and focus light, solving the chromatic aberration problem of the convex lenses.

Early in the 1900s would see construction of large research reflector telescopes designed for precision photographic imagining and located atop remote high altitude clear sky locations. This telescopes included the 60 inch Hale telescope built in 1908 and the 100 inch Hooker telescope, both of which were located in the Southern Mountains Ecoregion in southern California within the Transverse Ranges at Mount Wilson Observatory upon Mount Wilson, a 5.710 foot peak in the San Gabriel Mountains

The word magnitude in astronomy, unless stated otherwise, usually refers to a celestial object's apparent magnitude.

The apparent magnitude of a comet (or other celestial object) is the brightness that the object has as it appears to an observer on Earth.

The apparent magnitude depends on its intrinsic luminosity, its distance, and any extinction of the object′s light caused by interstellar dust along the line of sight to the observer.

The peak or absolute magnitude is one of the main parameters in the expression for the brightness of a comet.

It is expressed as the apparent magnitude a comet would have if it was observed when at a distance of 1 AU from both the Earth and the Sun.

In astrodynamics, orbital eccentricity of an astronomical object that revolves around the Sun is a parameter that determines the amount by which its orbit around another body deviates from a perfect circle. The parameter in which that satellite′s orbit results in a perfect circle is considered to be zero (0).

The planets within the Solar System have an orbital eccentricity of zero or very near zero and thus have a circular orbit around the Sun.

If a satellite (or any other object) entering the Solar System has an orbital eccentricity value between 0 and 1, then this will cause that satellite to be captured by the gravity of the Sun and thereafter have an elliptical shaped orbit around the Sun. This can also be referred to as a Elliptical Orbit, which is what most comets have.

As the eccentricity value increases from 0.01 to any higher level upwards to 0.99, then the higher that the eccentricity value becomes, will result in increasing the overall length of the elliptical orbit of the satellite (or comet).

For example: the eccentricity value closer to the 0.01 value will usually result in Short Period Comets. The eccentricity value closer to the 0.99 value will usually result in Long Period Comets.

If a satellite (or other object) entering the Solar System with the orbital eccentricity value of greater than 1, then that satellite, instead of obtaining an elliptical orbit and be captured by the Sun′s gravity, will obtain a hyperbolic orbit, also known as an escape orbit, which is an orbit which will cause the satellite to escape the gravitational restraints of the Sun and thereafter leave the solar system, never to return.

If in the rare occurrence, the orbital eccentricity of a satellite upon entering the Solar System, is equal to 1, then the satellite will be exactly on the border between the capture orbit and the escape orbit.

Then, any perturbations along the path of the orbit of this satellite can cause the satellite to goes either direction, either into a capture orbit (elliptic orbit) or into an escape orbit and thereafter be ejection from the solar system.

Short period comets are defined as those having an orbital period of less than 200 years. These orbits generally have an orbit which takes them out to the region of the outer planets to reach their aphelion before returning towards the sun. (Example: Comet Encke: about 3.3 year period)

Short period comets usually orbit along or close to the ecliptic plane in the same direction as the planets. There are families of comets which are grouped by where their aphelion. Such planets are thought to arise from the planet capturing formerly long-period comets into shorter orbits.

Because the orbit of short period comets frequently take the comet close to the giant planets, these comets are subject to further gravitation perturbations.

Long period comets are icy body object which have a highly eccentric orbits and an orbital period range of 200 and 1000 years. These comets come from the Kuiper belt and scattered disk, beyond the orbit of Pluto, with possible origins in the Oort cloud for many.

Due to the origin of their location, these comets are likely pristine relics from the early Solar System, and are known for spectacular appearances such as were Hale-Boop and Hyakutake. However, sometimes, due to their speed and size, these comets may pose a collision hazard with other celestial bodies within the Solar System.

There are galactic tides (a tidal force from within a galaxy and/or a passing star) around the outer edges of our Solar System which can give otherwise sedentary celestial objects a nudge causing that object to begin to move into the inner Solar System.

There is a third type of orbit which is termed as an ejection orbit meaning the comet has been ejected outside of the solar system and will not be returning.