One thing us as humans have never been able to fully understand is astronomy. Always having an unexplained mystery, astronomy also has served as a way to keep time and predict the future. The word astronomy is defined as the study of heavenly bodies, meaning anything in the sky such as stars, galaxies, comets, planets, nebulae, and so on. Many people, if not everyone, is amazed by the night sky on a clear, moonless night.

Astronomy dates back to ancient times when peoples such as the Babylonians, Egyptians, and Chinese kept written records of astronomical events and occurrences. Todays seven day week originates from the Babylonians seven important bodies in the night sky: the Sun, Moon, Mars, Mercury, Jupiter, Venus, and Saturn. The ancient Egyptians used the stars to align their pyramids and many of their corridors in almost perfect north-south or east-west directions. The Chinese were experts at predicting solar eclipses. They believed that a solar eclipse was a dangerous warning.

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Chinese astronomers were executed if they failed to predict an eclipse.Over the years there have been many more important figures in astronomy. One extraordinary astronomer was Galileo Galilei who invented the first refractor telescope in which light is bent to enlarge an image of the sky (Galileo Project). The next great astronomer to follow him was Isaac Newton. Newton had made a great amount of contributions to astronomy during his life.

He further proved that the Earth was not the center of the universe and he also invented the Newtonian reflector telescope which is still used today in observatories. Also, he discovered that light could be split into a visible spectrum of colors. Spectral colors from stars would later be used to determine their size, temperature, chemical composition, and even the direction the star is moving.Today, professional astronomers play a very different role than hundreds of years ago. Surprisingly, astronomers today spend minimal time at the telescope gazing at the night sky. Operating planetariums, teaching astronomy classes, or operating and maintaining an observatory are some of the things astronomers today do.

Along with professional astronomers are amateur astronomers who only observe the heavens for personal satisfaction and enjoyment. I myself am an amateur astronomer and enjoy observing everything in the night sky with a 5-inch Newtonian reflector. Amateurs help professionals by keeping a watch for new discoveries of comets, asteroids, and other bodies that professionals dont have time to scan the sky for.

A wide array of instruments is used to observe heavenly bodies today. These instruments include optical telescopes which are used to magnify objects that emit visible light. Some celestial bodies are very difficult or impossible to see with optical telescopes. To see these, we use radio, X-ray, ultraviolet, or infrared instruments. An advantage of radio astronomy is the fact that radio waves arent stopped by the sun or clouds, therefore the stars can be observed at any time.

Our own solar system today is thought to have formed from a large, single cloud of dust and gas. The center of the cloud became dense enough and created enough energy from contraction to spark a nuclear reaction, forming the Sun. The remaining dust and ice in the cloud formed into the nine planets we know of today.

Other objects within the solar system include comets, asteroids, meteorites, interplanetary dust and plasma.Any star that we can see belongs to our own galaxy, the Milky Way. Stars do not exist outside of galaxies in empty space, rather in galaxies which are groups of billions of stars orbiting the center of the galaxy (Fradin 140). Every star has a color ranging from red to blue-white.

These colors tell us many things about each star. Also, a stars brightness is called its magnitude. Put in perspective, the magnitude of stars visible to the naked eye are all below 6. As the magnitude increases, the brightness of a star decreases.

The Milky Way contains single stars, such as our Sun, and also clusters of stars. Either open or globular, star clusters are made up of stars held together by their own gravity. One famous globular cluster that can be seen easily is the Great Cluster in the constellation Hercules.

From personal experience, observing these clusters with a telescope doesnt show much. Time lapse photography exposes details that cant be seen with telescope since more light is gathered in a longer amount of time. Some of the most beautiful sights in the sky are nebulae which are also contained within the Milky Way.

They are large clouds of dust and gas possibly from the explosion, or supernova, of another star.The night sky is also shared with other galaxies than our Milky Way. Galaxies can come in many sizes, ranging from those containing under a billion stars to over a trillion stars.

One of the closest galaxies to our own is the Andromeda Galaxy at only 2.2 million light years (Goldsmith 98). This is a very bright galaxy easily seen in the Andromeda constellation on winter nights near the zenith (straight overhead position). Two galaxies which are believed to revolve around our own are the Small and Large Magellanic Clouds.

Only visible from the Southern Hemisphere, Magellan, the famous European explorer, was the first to describe these galaxies.Even though we know a great amount more than the astronomers in the past, there is still an even larger amount we do not know about the universe to this day. Even our own solar system contains many questions yet to be answered. Some of these include the possibility of a planet beyond Pluto (Planet X), the means by which the system was created, and even the possibility of a sister star to the Sun named Nemesis. Another astronomical mystery is the creation of the universe. In time, many questions will be answered but some will always remain.

Astronomy is something that will never be completely understood.Works Cited:Goldsmith, Donald. The Astronomers. New York: St.

Martins Press,1991.Fradin, Dennis P. Astronomy. Chicago: Childrens Press, 1987.The Galileo Project. in History of Astronomy.

collection of sites(rev. Dec. 2002; accessed 6 Jan, 2002); available from http://www.cv.nrao.edu/fits/www/yp_history.html

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