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Nothing But the Facts About Astronomy

written by: Anurag Ghosh•edited by: Jason C. Chavis•updated: 5/23/2011

There are innumerable fascinating astronomy facts beyond our imagination. From the ancient Antikythera mechanism to modern-day amateur radio astronomy, the world is filled with many astronomical marvels and facts.

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    Interesting Facts about Astronomy

    Meaning of Astronomy:

    The word astronomy is derived from the Greek astronomia. Literally it means “law of the stars" (astron for “star" and nomos for “laws or culture"). In general, astronomy refers to the study of the physical and chemical properties of objects and matters outside Earth’s atmosphere. Below are some of top astronomy facts for space enthusisats:

    Ancient Astronomy Facts:

    Antikythera Mechanism • The Antikythera mechanism was the oldest known astronomical device. This ancient Greek device was used between 150-80 B.C. for calculating a planet’s movement. The device was discovered off the Greek island of Antikythera in an ancient shipwreck. Revered as the first ancestor of the astronomical computer, the Antikythera mechanism had some very modern features. The complexity of its bronze parts was similar to an 18th century clock. The device became popular for its use of a differential gear, which was previously believed to have been invented in the sixteenth century.

    • Ancient Babylonian astronomers applied mathematics to their predictions on any astronomical phenomena. The oldest written evidences of celestial phenomena were the ancient Babylonian cuneiform tablets called as Enuma Anu Enlil. Of these astronomical texts, Tablet 63, known as the Venus tablet of Ammisaduqa, records the visible risings of planet Venus over the period of 21 years. This was the earliest reference about planetary phenomena.

    • The writings of Homer and Hesiod included references about identifiable stars and constellations. In the classic Iliad and Odyssey, Homer refers to many constellations including Ursa Major, Orion, Pleiades, Bootes and Sirius, the Dog Star.

    • The name “planet" is derived from the Greek term planetes, meaning “wanderer".

    • Ancient Greeks thought that the morning and evening appearances of planet Venus represented two different objects. When Venus appeared in the eastern morning sky, it was called Phosphorus, or “light-bringer". When it appeared in the western evening sky, it was thought to be an “evening star" and was called Hesperus.

    • The geocentric model entered Greek astronomy in the 4th century BC. During this period, educated Greeks thought that Earth was The geocentric model_by Bartolomeu Velho at the center of the universe and the Sun, Moon, stars and other planets surrounded Earth. But, earlier theories about the heliocentric model were completely ignored. The earliest reference to a heliocentric model of the solar system was made in the 3rd century BCE by Aristarchus of Samos! Aristarchus is also known as the “Greek Copernicus".

    • The Indian astronomer Aryabhata’s (476-550 CE) writings greatly influenced Islamic astronomy. Aryabhata, in his books, Āryabhatīya and the Aryabhatasiddhanta, plainly mentioned that the earth rotated around its own axis. Aryabhata also stated that the moon shines because of reflected sunlight.

    (Image, top left: The Antikythera mechanism from the ship wreck courtesy:

    (Image, Bottom Right: Classic illustration of the Ptolemaic geocentric model of the universe by Bartolomeu Velho, from his work Cosmographia, France, 1568, image courtesy of:

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    Modern Astronomy Facts

    There are numerous books and encyclopedias abounding with modern astronomy facts. Below are some of the most interesting facts about modern astronomy. These include key astronomy facts about the Ptolemaic system, Galileo's telescope, the three laws of Johannes Kepler and Isaac Newton facts:

    • The Ptolemaic system, based on the geocentric model, was adopted by Claudius Ptolemaeus of Alexandria, Egypt in the 2nd century AD. Quite interestingly, the geocentric system was left unchallenged for more than 1400 years until Copernicus’s De revolutionibus orbium coelestium was published in 1543. The book explicitly challenged the geocentric model by proposing that the Earth and other planets revolved around the Sun.

    Galileo Galilei • The application of the telescope by Galileo Galilei in 1609 questioned the very foundation of geocentrism. With the help of his telescope, Galileo defended, corrected and expanded the heliocentric model challenging Ptolemy’s geocentrism.

    • In the year 1609 and 1619, Johannes Kepler constructed three laws that were based on the heliocentric view. He used these laws to predict the transit of Venus for the year 1631.

    • Isaac Newton devised the law of gravitation in 1678. The law of gravitation explained the motion of planets.

    • William Herschel discovered the planet Uranus in 1781.

    • The existence of the Milky Way, as a separate group of stars, and the existence of other external galaxies was proven in the 20th century by Edwin Hubble.

    (Image, Left: Painting of Galileo Galilei by Justus Sustermans, painted in 1636, image courtesy: )

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    Astronomy: Fun Facts

    Astronomy holds a wealth of amazing information one could ever imagine. Books after books have been written to coves these interesting facts about astronomy. Few astronomy fun facts including facts about galaxies, the comet Hale Bopp and neutron stars are presented in this section. Hope you will find these astronomy facts interesting and informative

    • On a clear night, the naked eye can only perceive about 3000 stars. Our galaxy alone has an estimated 1011 to 1012 stars and there are probably more than 1012 galaxies in the universe. With this simple calculation, there might be more than 1024 stars in the universe. (Source:

    • Even if you had the most sophisticated spacecraft that travels at the speed of light (speed of light=186,000 miles per second), it would take approx. 105 (one hundred thousand) years to cross the galaxy.

    • Comet Hale Bopp will pass Earth in the year 4937 AD.

    NeutronStar Neutron stars are created from the core of the massive stars during a supernova explosion. These are fascinating dense objects and are only 10 miles in diameter. One teaspoonful or sugar cube of neutron star weighs about 100 million tons. (Source:

    • The year 2009 is declared to be the International Year of Astronomy (IYA 2009). IYA 2009 celebrates astronomy and its immense contributions to various cultures and societies.

    • Amateur radio astronomy owes its birth to Karl Jansky. In the early 1930's Karl began observing the night sky at radio wavelengths. There are many radio telescopes available to amateur astronomers, for example: the One-Mile Telescope. These telescopes were first built for serious astronomy research, but are now available to amateur astronomers.

    (Image, Left: Neutron star RX J185635-3754 in visible light, photo credit: Fred Walter (State University of New York at Stony Brook) and NASA, image courtesy of

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