Astronomy

Astronomy Factors that Impact the Visibility of a Comet



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Comets have intrigued, fascinated and had man a little wary for more years than one could ever imagine. Most people find the presence of a comet lighting up the nigh sky quite magical and mesmerizing. While comets are no rarity to our solar system they are very seldom witnessed by the naked eye. Comets are in orbit around the sun just like the planets in our solar system are. Comets are composed of dust, ices and rock debris which is said to have carried from the early formation of the solar system well over 4.6 billion years ago. Where do they come from? Scientists state that comets are remnants from the outer cold regions of the solar system. A host of scientists believe that they come from the Oort Cloud and the Kuiper Belt.

These areas are said to be where materials which are left over from the formation of the solar system have become condensed into icy objects. They are said to still be part of our solar system even though they both extend beyond the orbits of Pluto and Neptune. A comet has three parts and these are; the nucleus, coma and the tail. The nucleus is the solid centre which is made up of ice, gas and rocky debris. The coma is the dust and gas around the nucleus which is the result of the heat from the sun after it warms the nucleus so that the gas spews forward in all directions. The coma is defined as a dense water cloud which is made up of carbon dioxide and neutral gases which come from the nucleus.

The dust tails are formed when the energy from the sun turns the coma so that it flows around the nucleus. It then forms what scientists call a ‘fanned tail’ behind it. These extend millions of miles through space. When we watch this through a telescope we see the coma and tail due to the sunlight reflecting off the dust. Due to the fact that the sun settles on some molecules and makes them glow and form a bluish type tail which is called an ion tail. It also forms a yellow tail which is made up of neutral sodium atoms. The ion tail consists of plasma. This is the part of the tail that is said to interact with the solar wind. Comets have been viewed by scientists which range from less than 1km in diameter up to an amazing 300km.

Comets are a very popular and intriguing space phenomenon. They are frequently nicknamed ‘dirty snowballs’ by astronomers. When the composition of comets are studied they can tell us a great deal about the history of the solar system. Without the sun, astronomers and those who enjoy gazing at the skies would not be able to see comets easily. This is because they reflect light from the sun. In fact many scientists deem this a comets light source. The sun is what actually helps form the various parts of a comet. As it nears the sun, its radiation evaporates the ice. When this happens the gases and dust are dragged from the nucleus. The radiation from the sun basically blows the dust from the head of the comet away. This then creates the dust tail. The solar wind then drags the ionized gas from the comet and creates the ion tail.

Perchance you have wondered where the comets go. Comets orbit around the sun yet their orbits are far more elongated and take longer to complete. The majority of these go far beyond Pluto. Periodic comets are those which have an orbit of less than 200 years. These type of comets actually make up the majority of comets we have known. How long they last is dependent on the comet’s orbit. Each time it passes the sun it loses a percentage of its ice and gases. By the time it has passed the sun approximately 500 times, most of the ice and gas is gone. The comet then turns into what many deem a type of asteroid. Comets have caused quite a stir throughout history, often being blamed for a host of tragedies.

Viewing a comet is an amazing and exciting event. Although we can now chart when and where they shall appear. Knowing the many factors that effect their visibility aids astronomers immensely. The size of your telescope aids in visibility and when comets are very small they are certainly hard to follow. Amateur astrologists can view approximately 12 comets a year. But as of May 2010, there are a reported 3,976 known comets of which approximately 1,500 are Kreutz Sungrazers while 484 are said to be short period. The number visible to the naked eye without the need for telescopes and so forth averages to one per year. Hale Bop and Halley's Comet can be see with binoculars or the naked eye. Others are so small or too far away to be seen without the use of a telescope.

With the use of information from various websites such as http://science.nasa.gov/ one can learn when and where a comet will make its appearance. Weather conditions also come into the equation and both low and high clouds can block your view of comets. Often times, high humidity, fog, water and evaporation will distort and infringe on your viewing opportunities. These can also fog up your binoculars and telescopes. Pollution in the air will also make it difficult to see a comet. This can be anything from industrial smoke, general smog or fire smoke. These can all create an airborne haze. Unfortunately light pollution can also interfere with you chances of viewing a comet. More so if you reside in an urban area. Light pollution can cause a glow which seems to settle on the entire town. This is caused by a plethora of light sources such as car headlights, household lights, street lights and so forth. One also has line of sight pollution to contend with.

Unfortunately a comet’s orbit can be elongated making viewing almost impossible. Therefore the comet is sometimes out of viewing range. The earth tilts on its axis and in doing so has a great effect on the seasons as well as what can be viewed in the skies above. Consequently someone in Australia won’t necessarily be seeing the same things in the sky as someone in a different hemisphere. It is also said that the higher the comet sits within the sky, the easier it is to view. Viewing a comet is a sensational experience and a very possible one. Now that you know the factors that impact the visibility of comets, your chances of viewing one have greatly increased.

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